Peripheral Nerve Block Techniques and Considerations
240 Questions
2 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which scenario best illustrates a contraindication for peripheral nerve block?

  • A patient requiring anesthesia for a routine dental procedure.
  • A patient with severe pulmonary disease undergoing an orthopedic procedure.
  • A patient with an active infection at the injection site preparing for thoracotomy. (correct)
  • A patient experiencing recurrent headaches seeking nerve block for chronic pain relief.

    • What is a significant advantage of using a regional technique over general anesthesia in patients with obstructive sleep apnea?

  • Higher likelihood of requiring postoperative oxygen therapy.
  • Enhanced sedation levels during the procedure.
  • Increased risk of intraoperative complications.
  • Reduction in opioid consumption during the perioperative period. (correct)

    • What is a potential drawback of performing procedures under regional anesthesia?

  • Surgical outcomes dependent on the effectiveness of the nerve block. (correct)
  • Greater patient cooperation required.
  • Increased perioperative pain management options.
  • Ability to adapt the surgical approach during the procedure.

    • How can local anesthetic injections benefit tissue perfusion during surgery?

    <p>By causing vasodilation at the block site.</p> Signup and view all the answers

    What is a characteristic of peripheral nerve block procedures in terms of administration?

    <p>They may involve a single injection or continuous infusion.</p> Signup and view all the answers

    What is the primary advantage of using an in-plane approach for ultrasound-guided nerve blocks?

    <p>It provides better visualization of the entire needle shaft.</p> Signup and view all the answers

    Which technique utilizes exsanguination and an inflated tourniquet before local anesthetic injection?

    <p>Bier block</p> Signup and view all the answers

    What is a major disadvantage of using ultrasound during nerve block procedures?

    <p>The need for specialized and expensive equipment.</p> Signup and view all the answers

    In nerve stimulation techniques, what does the disappearance of muscle twitching indicate?

    <p>The nerve is adequately surrounded by anesthetic.</p> Signup and view all the answers

    What does lateral resolution in sonographic imaging primarily depend on?

    <p>Width of the ultrasound beam and frequency of the wave.</p> Signup and view all the answers

    What is the appropriate course of action if a patient becomes pulseless during treatment?

    <p>Start cardiopulmonary resuscitation.</p> Signup and view all the answers

    Which of the following is NOT a primary benefit of performing an analgesic peripheral nerve block?

    <p>Enable avoidance of general anesthesia.</p> Signup and view all the answers

    What is a major contraindication for administering a peripheral nerve block?

    <p>A patient with anticoagulation therapy.</p> Signup and view all the answers

    Which brachial plexus block is primarily used for shoulder procedures due to its effectiveness?

    <p>Inter-scalene block.</p> Signup and view all the answers

    How should the patient be positioned for a supraclavicular nerve block?

    <p>Semi-sitting with the head turned to the opposite side.</p> Signup and view all the answers

    What should be done when a twitch response below 0.3 mA is obtained during a nerve stimulator block?

    <p>Withdraw the needle slightly and reassess.</p> Signup and view all the answers

    Which factor does NOT influence the duration of action of a local anesthetic?

    <p>Patient's age</p> Signup and view all the answers

    Which additive is known for decreasing the time to block onset by alkalinizing local anesthetic solutions?

    <p>Sodium bicarbonate</p> Signup and view all the answers

    Which type of ultrasound probe would be most suitable for visualizing deep structures like the subgluteal sciatic nerve?

    <p>Low frequency probe (2–5 MHz)</p> Signup and view all the answers

    What is a characteristic that distinguishes bupivacaine from ropivacaine?

    <p>Bupivacaine induces more motor blockade.</p> Signup and view all the answers

    What is the appropriate depth adjustment when visualizing nerves under ultrasound?

    <p>The depth must be set to locate the target nerve effectively.</p> Signup and view all the answers

    What is the initial step recommended in treating a patient exhibiting signs of LAST?

    <p>Immediately discontinue all local anesthetic administration.</p> Signup and view all the answers

    What are the components of the brachial plexus subdivisions?

    <p>Roots, trunks, divisions, cords, and branches</p> Signup and view all the answers

    Which of the following complications is specifically associated with interscalene and supraclavicular blocks?

    <p>Ipsilateral diaphragmatic paresis</p> Signup and view all the answers

    What is the appropriate technique to minimize the risk of complications during regional anesthesia?

    <p>Inject local anesthetic in small increments while aspirating before each injection.</p> Signup and view all the answers

    What is a key consideration when performing a supraclavicular nerve block to minimize the risk of pneumothorax?

    <p>Achieving excellent visualization of the needle tip during the procedure</p> Signup and view all the answers

    What is the medical rationale behind using a supplementary rescue block following inadequate analgesia in a supraclavicular nerve block?

    <p>To directly target the specific nerves that were inadequately blocked</p> Signup and view all the answers

    Which anatomical position is ideal for inserting the needle during an axillary nerve block?

    <p>Along the medial aspect of the arm in the axilla</p> Signup and view all the answers

    When considering nerve blocks for lower extremity surgery, what is an essential factor to evaluate regarding postoperative outcomes?

    <p>The need for postoperative motor function monitoring</p> Signup and view all the answers

    What is a common risk associated with the infraclavicular nerve block that requires special attention during the procedure?

    <p>Higher likelihood of intravascular injection</p> Signup and view all the answers

    Which of the following risks is NOT associated with nerve blocks in the lower extremity?

    <p>Complete anesthesia failure</p> Signup and view all the answers

    What differentiates a plane block from a standard peripheral nerve block?

    <p>Involves infiltration in fascial planes without distinct nerve identification</p> Signup and view all the answers

    Which nerve is primarily targeted during the Erector Spinae block?

    <p>Thoracic/lumbar spinal nerves</p> Signup and view all the answers

    What complication is specifically associated with paravertebral blocks due to their anatomical proximity?

    <p>Pneumothorax</p> Signup and view all the answers

    Which technique is indicated for managing pain during lower abdominal surgeries, such as hysterectomy?

    <p>Transversus Abdominis Plane (TAP) block</p> Signup and view all the answers

    What is a primary advantage of performing an erector spinae block compared to a paravertebral block?

    <p>It is lower risk for nerve damage due to its anatomical location.</p> Signup and view all the answers

    Why might a PECS block be favored over the paravertebral block for breast surgery?

    <p>It has a lower risk of complications and provides equivalent analgesia.</p> Signup and view all the answers

    What is a significant drawback of the quadratus lumborum block compared to the TAP block?

    <p>It is more challenging to perform.</p> Signup and view all the answers

    How does spinal anesthesia differ from epidural anesthesia regarding the volume of local anesthetic required?

    <p>Epidural anesthesia requires ten times the volume of local anesthetic.</p> Signup and view all the answers

    Which of the following correctly describes a characteristic of neuraxial anesthesia compared to general anesthesia?

    <p>It reduces the incidence of venous thromboembolic complications.</p> Signup and view all the answers

    What frequency probe is most suitable for visualizing deep structures like the subgluteal sciatic nerve?

    <p>2–5 MHz</p> Signup and view all the answers

    Which of the following techniques is least likely to help visualize the needle during an IP block?

    <p>Injecting the anesthetic before visualizing the tip</p> Signup and view all the answers

    Which of the following nerves is NOT a branch of the lumbar plexus?

    <p>Tibial nerve</p> Signup and view all the answers

    Which complication is NOT typically associated with interscalene nerve blocks?

    <p>Pneumothorax</p> Signup and view all the answers

    What structure forms the anterior border of the paravertebral space?

    <p>Parietal pleura</p> Signup and view all the answers

    What is a primary effect of adding epinephrine to local anesthetics?

    <p>Prolongation of block duration</p> Signup and view all the answers

    Which local anesthetic has the fastest onset time according to its properties?

    <p>2-Chloroprocaine</p> Signup and view all the answers

    In managing LAST, which initial treatment step is recommended?

    <p>Immediately discontinue all local anesthetics</p> Signup and view all the answers

    What common symptoms are seen during the excitatory phase of LAST?

    <p>Tinnitus and altered mental status</p> Signup and view all the answers

    What is the maximum intravenous lipid emulsion dose for patients experiencing LAST?

    <p>12 mL/kg</p> Signup and view all the answers

    Which of the following conditions makes a patient a poor candidate for a peripheral nerve block?

    <p>Chronic infection</p> Signup and view all the answers

    What factor primarily influences the duration of action of a local anesthetic?

    <p>Type of local anesthetic used</p> Signup and view all the answers

    Which brachial plexus block is considered most suitable for shoulder surgery?

    <p>Interscalene block</p> Signup and view all the answers

    What is the correct bolus dosing of intravenous lipid emulsion for patients weighing less than 70 kg?

    <p>1.5 mL/kg</p> Signup and view all the answers

    What is a recognized benefit of performing a peripheral nerve block for analgesia?

    <p>Reduces the need for postoperative medications and their side effects</p> Signup and view all the answers

    What is a potential consequence of intravascular injection during a nerve block procedure?

    <p>Systemic toxicity from local anesthetic</p> Signup and view all the answers

    In the context of paralysis from nerve blocks, what unique risk is associated with lumbar plexus blocks?

    <p>Bowel perforation</p> Signup and view all the answers

    Which of the following best describes a characteristic of the quadratus lumborum block compared to other truncal blocks?

    <p>It can block multiple spinal nerves simultaneously</p> Signup and view all the answers

    What distinguishes the risk of pleural puncture in paravertebral blocks from standard peripheral nerve blocks?

    <p>Anatomical proximity to the pleura</p> Signup and view all the answers

    Which factor contributes to the increased safety of the transversus abdominis plane (TAP) block compared to traditional methods?

    <p>Ultrasound guidance for correct placement</p> Signup and view all the answers

    What is one potential advantage of peripheral nerve blocks for patients with severe cardiopulmonary disease?

    <p>They can help avoid pulmonary complications during surgery.</p> Signup and view all the answers

    What could lead to inadequate sensory loss just prior to surgical incision in a patient receiving a peripheral nerve block?

    <p>Insufficient time allowed between the block and the incision.</p> Signup and view all the answers

    Why might procedures requiring cooperation from the patient be unsuitable for peripheral nerve blocks?

    <p>Patients are less likely to cooperate if they experience anxiety.</p> Signup and view all the answers

    What is one disadvantage of using peripheral nerve blocks as the primary anesthetic technique?

    <p>They may limit the surgeon's options if intraoperative findings change.</p> Signup and view all the answers

    Which of the following accurately describes a contraindication for peripheral nerve block?

    <p>Current infection at the injection site.</p> Signup and view all the answers

    What is a key advantage of using ultrasound guidance during peripheral nerve blocks compared to traditional techniques?

    <p>It provides better visualization of anatomical structures and blood vessels.</p> Signup and view all the answers

    In the Bier block technique, what is the purpose of exsanguinating the limb before injection?

    <p>To ensure the local anesthetic is distributed evenly.</p> Signup and view all the answers

    What aspect of the nerve stimulator technique can potentially complicate its use?

    <p>The possibility of muscle twitching being misidentified as nerve stimulation.</p> Signup and view all the answers

    Which characteristic differentiates the in-plane (IP) approach from the out-of-plane (OP) approach in ultrasound-guided nerve blocks?

    <p>The IP approach allows visualization of the entire needle shaft.</p> Signup and view all the answers

    What is a notable disadvantage of utilizing ultrasound equipment in nerve block procedures?

    <p>It may not be portable and requires high maintenance costs.</p> Signup and view all the answers

    What is the primary reason for positioning the arm above the head during an infraclavicular nerve block?

    <p>To elevate the clavicle and increase room for the ultrasound probe</p> Signup and view all the answers

    Which type of brachial plexus block poses the greatest risk of pneumothorax?

    <p>Supraclavicular nerve block</p> Signup and view all the answers

    When achieving complete surgical anesthesia for lower extremity procedures, which blocks would typically be combined?

    <p>Popliteal sciatic and saphenous nerve blocks</p> Signup and view all the answers

    What anatomical feature poses a challenge for adequate anesthesia in the supraclavicular nerve block?

    <p>The proximity of the lower trunk in the corner pocket</p> Signup and view all the answers

    What is a key factor to ensure when performing an infraclavicular nerve block to avoid complications?

    <p>Aspiration before every injection to check for intravascular placement</p> Signup and view all the answers

    What is a notable disadvantage of the erector spinae block as compared to the paravertebral block?

    <p>Its benefits are not well described in the literature.</p> Signup and view all the answers

    Which of the following correctly compares the characteristics of spinal anesthesia to epidural anesthesia?

    <p>Spinal anesthesia involves puncturing the dura, while epidural anesthesia does not.</p> Signup and view all the answers

    What is a key advantage of performing PECS blocks over paravertebral blocks specifically for breast surgery?

    <p>PECS blocks carry a lower risk of complications than paravertebral blocks.</p> Signup and view all the answers

    Which of the following statements about the TAP and quadratus lumborum blocks is correct?

    <p>Quadratus lumborum blocks cannot be performed while the patient is supine.</p> Signup and view all the answers

    What is the primary reason neuraxial anesthesia can be preferred over general anesthesia in certain surgical scenarios?

    <p>It maintains the patient’s mental status and avoids airway manipulation.</p> Signup and view all the answers

    Which condition is a contraindication for performing a peripheral nerve block?

    <p>Coagulopathy</p> Signup and view all the answers

    What is a notable disadvantage of using peripheral nerve blocks compared to general anesthesia?

    <p>Patient cooperation is required</p> Signup and view all the answers

    What are the two primary methods of administering regional anesthesia?

    <p>Single injection or continuous infusion via catheter</p> Signup and view all the answers

    In which scenario would regional anesthesia be particularly advantageous?

    <p>When dealing with anticipated difficult airways</p> Signup and view all the answers

    Which of the following is an effect of local anesthetic injection at the block site?

    <p>Vasodilation</p> Signup and view all the answers

    What is the primary reason for adding sodium bicarbonate to local anesthetic solutions?

    <p>To alkalinize the pH and increase the nonionized form</p> Signup and view all the answers

    Which local anesthetic has the potential for higher cardiotoxicity?

    <p>Bupivacaine</p> Signup and view all the answers

    Which response should NOT be expected after an intravascular injection of epinephrine?

    <p>Decreased blood pressure</p> Signup and view all the answers

    What factor influences the duration of action of local anesthetics MOST significantly?

    <p>Presence of a vasoconstrictor</p> Signup and view all the answers

    Which stage is characterized by seizures and altered mental status in the event of LAST?

    <p>Excitatory phase</p> Signup and view all the answers

    What is a significant risk associated with performing a Bier block due to the method of local anesthetic delivery?

    <p>Increased risk of systemic toxicity from rapid absorption</p> Signup and view all the answers

    In the context of ultrasound-guided nerve blocks, what is a primary disadvantage of the out-of-plane approach compared to the in-plane approach?

    <p>Limited visualization of local anesthetic spread</p> Signup and view all the answers

    What is the maximum intravenous lipid emulsion dose for a patient experiencing LAST?

    <p>12 mL/kg</p> Signup and view all the answers

    How does the nerve stimulator technique confirm needle placement, and what could complicate this process?

    <p>By eliciting muscle twitching; however, direct muscle stimulation can mimic nerve response</p> Signup and view all the answers

    Which of the following patients is least suitable for receiving a peripheral nerve block?

    <p>A patient on anticoagulants with a known history of bleeding disorders</p> Signup and view all the answers

    What crucial factor can influence the axial resolution in ultrasound imaging for nerve blocks?

    <p>The frequency of the ultrasound transducer</p> Signup and view all the answers

    Which brachial plexus block provides anesthesia from the mid-humerus to the fingers but often spares a key nerve requiring a separate block?

    <p>Axillary block</p> Signup and view all the answers

    What limitation is commonly associated with anatomic landmark techniques for peripheral nerve blocks compared to ultrasound guidance?

    <p>Reduced effectiveness due to anatomical variations</p> Signup and view all the answers

    What is the recommended bolus dose of intravenous lipid emulsion for a patient weighing less than 70 kg experiencing LAST?

    <p>1.5 mL/kg</p> Signup and view all the answers

    What position should a patient be in for performing a supraclavicular nerve block?

    <p>Semi-sitting with the head turned to the opposite side</p> Signup and view all the answers

    Which statement accurately describes the relationship between ultrasound probe frequency and structure visualization?

    <p>High frequency probes provide the best resolution for superficial structures.</p> Signup and view all the answers

    What nerve roots contribute to the formation of the lumbar plexus?

    <p>T12–L4</p> Signup and view all the answers

    Which of these complications is specifically associated with interscalene and supraclavicular nerve blocks?

    <p>Horner syndrome due to sympathetic chain involvement</p> Signup and view all the answers

    Which branch of the brachial plexus arises from the medial cord?

    <p>Ulnar nerve</p> Signup and view all the answers

    What procedure best facilitates visualization of an interscalene block needle aligned with the ultrasound beam?

    <p>Positioning the needle parallel to the plane of the probe</p> Signup and view all the answers

    What specific anatomical consideration is crucial to avoid during a supraclavicular nerve block?

    <p>Location variability of the subclavian artery</p> Signup and view all the answers

    Which nerve block method requires multiple injections for effective circumferential anesthesia of the upper extremity?

    <p>Axillary nerve block</p> Signup and view all the answers

    What is a significant risk associated with the infraclavicular nerve block compared to the axillary block?

    <p>Increased risk of intravascular injection</p> Signup and view all the answers

    When performing a rescue block due to inadequate supraclavicular nerve block, what theoretical risk should be taken into account?

    <p>Nerve damage from repeated needle passage</p> Signup and view all the answers

    In terms of anatomical landmarks for a lumbar plexus block, which landmark is essential for the needle insertion point?

    <p>4-5 cm lateral to the L4-L5 interspace</p> Signup and view all the answers

    What is the primary risk associated with lumbar plexus blocks due to its anatomical positioning?

    <p>Aortic perforation with retroperitoneal hematoma</p> Signup and view all the answers

    Which factor contributes to the need for higher volumes of local anesthetic in plane blocks compared to peripheral nerve blocks?

    <p>The technique's reliance on infiltrating fascial planes</p> Signup and view all the answers

    Which nerve is primarily affected by the quadratus lumborum block?

    <p>Thoracic spinal nerves</p> Signup and view all the answers

    In a paravertebral block, what complication arises due to its close association with the pleura?

    <p>Pneumothorax from pleural puncture</p> Signup and view all the answers

    What is a significant disadvantage of using truncal nerve blocks compared to regular peripheral nerve blocks?

    <p>Possibility of unintended hemodynamic changes</p> Signup and view all the answers

    What is a distinguishing feature of spinal anesthesia compared to epidural anesthesia?

    <p>Spinal anesthesia involves direct injection into the intrathecal space.</p> Signup and view all the answers

    Which statement correctly describes the relative effectiveness of the quadratus lumborum block compared to the TAP block?

    <p>The quadratus lumborum block may cover more dermatomes per injection.</p> Signup and view all the answers

    What is a significant limitation when performing the quadratus lumborum block?

    <p>It may pose challenges related to patient positioning.</p> Signup and view all the answers

    Which of the following statements best describes a drawback of the erector spinae block?

    <p>It is less effective in providing analgesia compared to the paravertebral block.</p> Signup and view all the answers

    What is a primary benefit of neuraxial anesthesia over general anesthesia?

    <p>Reduction of the total systemic dose of anesthetics used.</p> Signup and view all the answers

    What might indicate that the tip of the needle is intraneural when providing nerve stimulation blocks?

    <p>A twitch response below 0.3 mA</p> Signup and view all the answers

    Which local anesthetic is specifically noted for its rapid metabolism and low toxicity risk when used in high concentrations?

    <p>2-Chloroprocaine</p> Signup and view all the answers

    What is the effect of adding sodium bicarbonate to local anesthetics prior to injection?

    <p>Decreases the time to block onset</p> Signup and view all the answers

    What potential side effect can occur with lidocaine in comparison to other local anesthetics?

    <p>Greater risk of LAST</p> Signup and view all the answers

    Which factor does NOT influence a local anesthetic's duration of action?

    <p>Patient's mental status</p> Signup and view all the answers

    What specific risk is often associated with lumbar plexus blocks due to their depth and anatomical proximity?

    <p>Bowel perforation</p> Signup and view all the answers

    Which truncal nerve block is performed by depositing local anesthetic between the internal oblique and transversus abdominis muscles?

    <p>TAP block</p> Signup and view all the answers

    What distinguishes a plane block from a standard peripheral nerve block in terms of nerve recognition?

    <p>No distinct nerve needs to be located</p> Signup and view all the answers

    Which of the following statements about the saphenous nerve is true?

    <p>It is typically blocked deep to the sartorius muscle.</p> Signup and view all the answers

    What anatomical consideration should be taken into account to avoid complications during a supraclavicular nerve block?

    <p>Presence of the phrenic nerve</p> Signup and view all the answers

    What should be considered a rare yet serious complication of paravertebral blocks?

    <p>Pneumothorax due to pleural puncture</p> Signup and view all the answers

    What is the primary reason for ensuring U-shaped spread of anesthetic during a brachial plexus block?

    <p>To avoid medial or lateral cord sparing</p> Signup and view all the answers

    What anatomical landmark is used to locate the lumbar plexus block for nerve stimulation?

    <p>Top of the iliac crest</p> Signup and view all the answers

    In the context of a supraclavicular nerve block, which potential complication is linked to inadequate anesthetic distribution in the lower trunk?

    <p>Ulnar nerve sparing</p> Signup and view all the answers

    What is a critical aspect of performing an infraclavicular nerve block that differs from the axillary nerve block?

    <p>Needle insertion is done at a shallower angle</p> Signup and view all the answers

    What is the appropriate bolus dose of intravenous lipid emulsion for patients weighing less than 70 kg experiencing LAST?

    <p>1.5 mL/kg bolus followed by a 0.25 mL/kg/min infusion</p> Signup and view all the answers

    Which of the following agents should be avoided in the treatment of a hemodynamically unstable patient experiencing LAST?

    <p>Lidocaine</p> Signup and view all the answers

    What is a primary risk factor that could contraindicate a patient from receiving a peripheral nerve block?

    <p>Anticoagulation therapy</p> Signup and view all the answers

    In which anatomical position should a patient be placed for administering a supraclavicular nerve block?

    <p>Sitting with head turned to the opposite side</p> Signup and view all the answers

    What is one of the limitations of the supraclavicular brachial plexus block?

    <p>High likelihood of phrenic nerve blockade</p> Signup and view all the answers

    What is the main reason for choosing the in-plane approach over the out-of-plane approach in ultrasound-guided nerve blocks?

    <p>It provides better visualization of the entire trajectory of the needle.</p> Signup and view all the answers

    What is a significant disadvantage of the nerve stimulator technique in administering peripheral nerve blocks?

    <p>It may cause unintentional nerve trauma due to lack of visualization.</p> Signup and view all the answers

    What factor primarily influences the axial resolution in sonographic imaging?

    <p>The number of cycles per pulse and pulse wavelength.</p> Signup and view all the answers

    Which factor is NOT a recommended consideration when performing a Bier block?

    <p>Use a high dose of lidocaine to ensure effective analgesia.</p> Signup and view all the answers

    In ultrasound-guided nerve blocks, what advantage does visualization of blood vessels provide?

    <p>It improves the accuracy of identifying neural structures.</p> Signup and view all the answers

    What is the significance of choosing the appropriate probe frequency for ultrasound visualization of nerves?

    <p>It allows for optimal resolution based on the depth of the target structure.</p> Signup and view all the answers

    Which layer of the abdominal muscles is innervated by the anterior rami of T7–L1?

    <p>External oblique</p> Signup and view all the answers

    From which nerve roots does the lumbar plexus derive, and what is an effective block for that area?

    <p>T12–L4 and fascia iliaca block</p> Signup and view all the answers

    What type of issues can arise from performing regional anesthesia techniques?

    <p>Ipsilateral Horner syndrome and phrenic nerve involvement.</p> Signup and view all the answers

    How can one optimize visualization of the needle during an injection under ultrasound guidance?

    <p>By increasing the distance from the probe when puncturing the skin.</p> Signup and view all the answers

    Which of the following statements about the PECS block is true?

    <p>It effectively blocks the pectoral nerves, which are not blocked by other techniques.</p> Signup and view all the answers

    What is a notable disadvantage of the erector spinae block compared to the paravertebral block?

    <p>Its effectiveness in delivering analgesia is unclear in current literature.</p> Signup and view all the answers

    In regards to the quadratus lumborum block, which statement is most accurate?

    <p>It provides broader dermatomal coverage than the TAP block per injection.</p> Signup and view all the answers

    What differentiates spinal anesthesia from epidural anesthesia in terms of local anesthetic administration?

    <p>Spinal anesthesia requires penetrating the dura and injecting into the cerebrospinal fluid.</p> Signup and view all the answers

    Which of the following is a primary advantage of neuraxial anesthesia over general anesthesia?

    <p>It typically results in lower total systemic drug doses.</p> Signup and view all the answers

    Which of the following conditions may indicate the use of regional anesthesia over general anesthesia?

    <p>Presence of chronic obstructive pulmonary disease (COPD)</p> Signup and view all the answers

    Which of the following is considered a significant disadvantage of using peripheral nerve blocks?

    <p>Inflexibility if intraoperative findings require broader anesthesia coverage</p> Signup and view all the answers

    What is a common contraindication when considering a peripheral nerve block?

    <p>Severe systemic infection or sepsis</p> Signup and view all the answers

    Which situation might warrant the need for continuous infusion of local anesthetic via catheter as opposed to a single injection?

    <p>A complex procedure requiring prolonged anesthesia and pain control</p> Signup and view all the answers

    What potential issue could arise from insufficient timing between a nerve block and surgical incision?

    <p>Inadequate sensory loss at the surgical site</p> Signup and view all the answers

    Which of the following is NOT typically considered a contraindication for peripheral nerve block?

    <p>Uncontrolled hypertension</p> Signup and view all the answers

    What is a major disadvantage of regional anesthesia compared to general anesthesia?

    <p>Requirement for patient cooperation during the procedure</p> Signup and view all the answers

    Which statement accurately describes a risk associated with peripheral nerve blocks?

    <p>Intraoperative findings may sometimes reveal the need for anesthesia in areas not covered by the block.</p> Signup and view all the answers

    How might local anesthetic injection improve surgical outcomes?

    <p>By enhancing perfusion of flaps or impaired extremities</p> Signup and view all the answers

    In what scenario would regional anesthesia be particularly beneficial?

    <p>For patients with an anticipated difficult airway</p> Signup and view all the answers

    What is the recommended maximum dosage of lidocaine for a Bier block procedure?

    <p>3 mg/kg</p> Signup and view all the answers

    Which of the following is the most significant disadvantage of using the out-of-plane approach in ultrasound-guided nerve blocks?

    <p>Poor visualization of the entire needle trajectory</p> Signup and view all the answers

    What is the main advantage of utilizing ultrasound guidance for performing peripheral nerve blocks?

    <p>Improves visualization of anatomical structures</p> Signup and view all the answers

    In the nerve stimulator technique, what does a consistent response at low amplitudes below 0.3 mA indicate?

    <p>Needle is near the targeted nerve</p> Signup and view all the answers

    Which type of resolution in sonographic imaging is primarily concerned with the ability to distinguish between two adjacent structures?

    <p>Lateral resolution</p> Signup and view all the answers

    What is the range of nerve roots that form the lumbar plexus?

    <p>T12–L4</p> Signup and view all the answers

    Which of the following blocks specifically targets the brachial plexus?

    <p>Interscalene block</p> Signup and view all the answers

    How should the needle orientation be adjusted to optimize its visualization during an IP block?

    <p>Ensure it is aligned with the ultrasound beam</p> Signup and view all the answers

    Which muscle layers of the abdomen are innervated by the anterior rami of T7–L1?

    <p>External oblique, internal oblique, transverse abdominis</p> Signup and view all the answers

    What is a significant facial complication associated with interscalene and supraclavicular blocks?

    <p>Horner syndrome</p> Signup and view all the answers

    What characterizes the excitatory phase of Local Anesthetic Systemic Toxicity (LAST)?

    <p>Tinnitus and circumoral numbness</p> Signup and view all the answers

    Which of the following factors predominantly influences the duration of action of local anesthetics?

    <p>Lipid solubility and protein binding</p> Signup and view all the answers

    What is the recommended action when a twitch response is observed below 0.3 mA during a nerve stimulator block?

    <p>Withdraw the needle and reassess placement</p> Signup and view all the answers

    Why might sodium bicarbonate be added to local anesthetic solutions?

    <p>To alkalinize the pH and decrease onset time</p> Signup and view all the answers

    In treating LAST, what is the primary action to take immediately when signs are observed?

    <p>Discontinue all local anesthetics and call for help</p> Signup and view all the answers

    What is a unique risk associated with a lumbar plexus block compared to standard nerve blocks?

    <p>Aortic perforation with retroperitoneal hematoma</p> Signup and view all the answers

    For which type of surgical procedure is the transversus abdominis plane (TAP) block particularly indicated?

    <p>Hysterectomy</p> Signup and view all the answers

    Which anatomical structures do the quadratus lumborum block primarily target for surgical anesthesia?

    <p>Thoracic and lumbar spinal nerves</p> Signup and view all the answers

    What is a common characteristic of truncal blocks like the erector spinae block?

    <p>Involves injection into a fascial plane</p> Signup and view all the answers

    What potential complication is particularly relevant to the paravertebral block technique?

    <p>Inadvertent intrathecal injection</p> Signup and view all the answers

    Which statement accurately describes a disadvantage of the erector spinae block compared to the paravertebral block?

    <p>Its benefits are not well described in the literature.</p> Signup and view all the answers

    What is a key reason why PECS or serratus anterior blocks may be preferred for breast surgery over paravertebral blocks?

    <p>PECS blocks are easier to perform and block pectoral nerves.</p> Signup and view all the answers

    Which characteristic distinguishes a spinal anesthetic from an epidural anesthetic?

    <p>Spinal anesthesia requires puncturing the dura.</p> Signup and view all the answers

    Which of the following is a disadvantage of the quadratus lumborum block compared to the TAP block?

    <p>It cannot be performed in the sitting position.</p> Signup and view all the answers

    What accurately describes the relationship between local anesthetic concentration and the effectiveness of analgesia or anesthesia?

    <p>Intense motor blockade occurs only with high local anesthetic concentrations.</p> Signup and view all the answers

    What dosing strategy should be employed for patients weighing more than 70 kg receiving intravenous lipid emulsion for LAST?

    <p>100 mL over 2 to 3 minutes, followed by 200 to 250 mL over 15 to 20 minutes</p> Signup and view all the answers

    Which of the following is NOT a common reason to avoid administering a peripheral nerve block?

    <p>Patient preference for procedure under general anesthesia</p> Signup and view all the answers

    What major complication is specifically associated with supraclavicular blocks?

    <p>Phrenic nerve blockade leading to respiratory issues</p> Signup and view all the answers

    What should the initial treatment step be if a patient exhibits symptoms of local anesthetic systemic toxicity (LAST)?

    <p>Initiate cardiopulmonary resuscitation if the patient is pulseless</p> Signup and view all the answers

    Which brachial plexus block is ideally suited for anesthesia during shoulder surgery?

    <p>Interscalene block</p> Signup and view all the answers

    What anatomical consideration is crucial for safely advancing the needle during a supraclavicular nerve block?

    <p>Proximity to the subclavian artery</p> Signup and view all the answers

    Which nerve block technique carries the least risk of complications among the supraclavicular, infraclavicular, and axillary approaches?

    <p>Axillary nerve block</p> Signup and view all the answers

    In a case of incomplete analgesia following a supraclavicular block, which is the most likely nerve to be inadequately blocked?

    <p>Ulnar nerve</p> Signup and view all the answers

    Which factor should be prioritized when selecting a nerve block for lower extremity surgery involving a thigh tourniquet?

    <p>Proximity of the nerves to the surgical site</p> Signup and view all the answers

    Which approach is critical to minimizing the risk of intravascular injection during an infraclavicular nerve block?

    <p>Ultrasound guidance with excellent visualization</p> Signup and view all the answers

    What is one reason regional anesthesia may not be suitable for certain patients during procedures?

    <p>They may have high anxiety or altered mental status.</p> Signup and view all the answers

    Which of the following is a significant disadvantage of using regional anesthesia in cases where intraoperative findings change?

    <p>It may not cover areas needing surgical intervention.</p> Signup and view all the answers

    What is a common outcome seen in patients with regards to sensory loss before incision when undergoing regional anesthesia?

    <p>They may perceive inadequate sensory loss.</p> Signup and view all the answers

    Which condition is considered a contraindication for performing a peripheral nerve block?

    <p>Infection at the injection site.</p> Signup and view all the answers

    In which scenario would regional anesthesia be particularly advantageous?

    <p>Patients with severe cardiopulmonary disease.</p> Signup and view all the answers

    Which probe frequency is most appropriate for visualizing superficial structures like ankle nerves?

    <p>10-13 MHz</p> Signup and view all the answers

    Which nerves arise specifically from the lumbar plexus?

    <p>Ilioinguinal and Iliohypogastric</p> Signup and view all the answers

    What anatomical structure forms the posterior boundary of the paravertebral space?

    <p>Superior costotransverse ligament</p> Signup and view all the answers

    What condition may occur due to phrenic nerve involvement in interscalene and supraclavicular nerve blocks?

    <p>Ipsilateral diaphragmatic paresis</p> Signup and view all the answers

    Which of the following procedures can potentially lead to a pneumothorax?

    <p>Supraclavicular block</p> Signup and view all the answers

    What is the primary method for performing a Bier block?

    <p>Exsanguinating the limb and injecting lidocaine after inflating double tourniquets</p> Signup and view all the answers

    In ultrasound-guided nerve block procedures, what is a significant advantage of the in-plane (IP) approach over the out-of-plane (OP) approach?

    <p>It allows for better visualization of the entire needle shaft</p> Signup and view all the answers

    What is one of the primary challenges associated with the nerve stimulator technique for nerve blocks?

    <p>It may elicit responses from direct muscle stimulation, confusing the results</p> Signup and view all the answers

    Which factor has the most impact on the axial resolution in sonographic imaging?

    <p>Pulse wavelength and number of cycles per pulse</p> Signup and view all the answers

    What is a disadvantage of using ultrasound guidance in nerve blocks?

    <p>It requires specialized equipment that may not be readily available</p> Signup and view all the answers

    What is the primary reason for adding epinephrine to local anesthetics in regional anesthesia?

    <p>To prevent systemic absorption and prolong block duration</p> Signup and view all the answers

    Which factor is the primary influence on the onset of action of a local anesthetic?

    <p>pKa of the local anesthetic</p> Signup and view all the answers

    What differentiates LAST-associated symptoms in the central nervous system from cardiovascular symptoms?

    <p>CNS symptoms always occur rapidly before cardiovascular symptoms.</p> Signup and view all the answers

    Which statement accurately describes the metabolism of 2-chloroprocaine?

    <p>It is rapidly metabolized by plasma cholinesterases.</p> Signup and view all the answers

    What is the recommended initial action if a patient exhibits signs of LAST?

    <p>Discontinue all local anesthetic administration immediately.</p> Signup and view all the answers

    What is the maximum intravenous lipid emulsion dose for patients experiencing LAST?

    <p>12 mL/kg</p> Signup and view all the answers

    Which condition represents a primary reason to avoid offering a nerve block to a patient?

    <p>Systemic infection</p> Signup and view all the answers

    What is a significant limitation of the supraclavicular brachial plexus block?

    <p>Increased risk of pneumothorax</p> Signup and view all the answers

    What is the appropriate bolus dose for patients weighing less than 70 kg receiving intravenous lipid emulsion for LAST?

    <p>1.5 mL/kg</p> Signup and view all the answers

    In which scenario would a nerve block be particularly beneficial?

    <p>Minimizing the risk of airway complications</p> Signup and view all the answers

    What complication is particularly associated with the supraclavicular nerve block due to its anatomical proximity?

    <p>Pneumothorax</p> Signup and view all the answers

    Which anatomical landmark is most appropriate for needle insertion in a lumbar plexus block?

    <p>Top of the iliac crest</p> Signup and view all the answers

    Which statement best describes the technique used for performing an axillary nerve block?

    <p>Multiple injections are required for complete circumferential spread.</p> Signup and view all the answers

    What is a potential consequence of inadequate local anesthetic in the supraclavicular nerve block?

    <p>Ulnar nerve sparing from inadequate block</p> Signup and view all the answers

    Which factor should NOT be considered when selecting the appropriate nerve block for lower extremity surgery?

    <p>Patient's weight</p> Signup and view all the answers

    What is the primary advantage of the quadratus lumborum block compared to the TAP block?

    <p>It covers a greater number of dermatomes per injection</p> Signup and view all the answers

    Which technique is associated with a lower risk of direct injury or hematoma compared to the paravertebral block?

    <p>Erector spinae block</p> Signup and view all the answers

    In which scenario would analgesia be typically preferred over anesthesia?

    <p>For postoperative pain management after surgery</p> Signup and view all the answers

    What is a significant disadvantage of using the erector spinae block compared to the paravertebral block?

    <p>Less effective analgesia likely</p> Signup and view all the answers

    Which aspect of neuraxial anesthesia contributes to its advantages over general anesthesia?

    <p>Preservation of mental status during surgery</p> Signup and view all the answers

    What anatomical landmarks are important for locating the proximal sciatic nerve?

    <p>Deep to the gluteus maximus and between the ischial tuberosity and greater trochanter</p> Signup and view all the answers

    Which of the following nerve blocks poses a risk of pneumothorax?

    <p>Paravertebral block</p> Signup and view all the answers

    When performing a plane block, what is the primary reason for needing a higher volume of local anesthetic compared to a standard peripheral nerve block?

    <p>Individual nerves are not distinctly identified, necessitating broader coverage.</p> Signup and view all the answers

    What unique risks are associated with a lumbar plexus block compared to other peripheral nerve blocks?

    <p>Aortic perforation and retroperitoneal hematoma</p> Signup and view all the answers

    In what specific location would you expect to block the saphenous nerve?

    <p>Deep to the sartorius muscle inside the adductor canal</p> Signup and view all the answers

    Study Notes

    Regional Anesthesia: Indications and Contraindications

    • Indications: Surgical anesthesia and/or intra- and postoperative analgesia for various surgeries including orthopedic procedures, amputations, thoracotomies, laparotomies, arteriovenous fistula creations/revisions, and mastectomies.
    • Contraindications: Patient refusal, sepsis/bacteremia, infection at injection site, preexisting neuropathy, and coagulopathy.

    Advantages and Disadvantages of Regional Anesthesia vs. General Anesthesia

    • Advantages: Useful in cases where general anesthesia is undesirable, such as patients with anticipated difficult airway or severe cardiopulmonary disease.
    • Advantages: Opioid-sparing effects are beneficial for perioperative pain control in patients with specific conditions like obstructive sleep apnea, severe postoperative nausea and vomiting, chronic opioid therapy, opioid abuse history, or allergies to analgesics.
    • Advantages: Local anesthetic injection can aid in perfusion of flaps or extremities with compromised perfusion due to vasodilation.
    • Disadvantages: Requires patient cooperation and may be unsuitable for children or patients with high anxiety, developmental delay, altered mental status, or dementia.
    • Disadvantages: Inadequate sensory loss before surgical incision can occur due to incomplete nerve block or insufficient time between block and incision.
    • Disadvantages: Preoperative blocks may lack flexibility if intraoperative findings necessitate changes in surgical approach.

    Methods of Regional Anesthesia

    • Peripheral Nerve Blocks: Can be performed as a single injection or a continuous infusion via indwelling catheter.
    • Neuraxial Blockade: Performed as an injection into the subarachnoid space (spinal anesthesia) or a continuous infusion into the epidural space.
    • IV Regional Anesthesia (Bier Block): Local anesthetic is injected intravenously into an extremity in the presence of an inflated tourniquet.

    Bier Block Technique

    • IV placement in the operative extremity.
    • Extremity elevation and exsanguination through compression bandage application.
    • Inflation of a double tourniquet.
    • Intravenous injection of lidocaine (≤ 3 mg/kg) into the operative extremity.
    • Limb lowering, IV removal, and surgical procedure initiation.
    • Patient breathes spontaneously with or without sedation.
    • Typically used for procedures lasting 30 to 45 minutes.

    Peripheral Nerve Block Techniques

    • Ultrasound Guidance: Visualizes local anesthetic spread around neural structures.
    • Nerve Stimulation: Electrical stimulus through an insulated block needle elicits muscle twitching or paresthesias.
    • Anatomic Landmarks: Blocks performed using anatomical landmarks alone or via subcutaneous infiltration.

    Ultrasound Guided Nerve Block Technique

    • Technique: Ultrasound images guide needle advancement and local anesthetic injection around neural structures.
    • IP Approach: Needle advanced in the plane of the ultrasound beam, visualizing the entire needle shaft.
    • OP Approach: Needle advanced perpendicular to the ultrasound beam, visualizing only a cross-section of the needle.
    • Advantages: Better visualization of anatomical structures, decreasing complications like bleeding, hematoma formation, and pneumothorax risk.
    • Advantages: Identifies anatomical variations that might limit block effectiveness.
    • Advantages: Visualizes nerves, ensuring complete neural structure coverage by local anesthetic.
    • Disadvantage: Requires specialized and expensive equipment.

    Nerve Stimulator Technique

    • Technique: Electrical stimulus emitted through an insulated block needle elicits muscle twitching or paresthesias specific to the targeted nerve.
    • Advantages: Confirms needle tip location.
    • Disadvantages: Potential for unintentional nerve trauma, inability to identify variant anatomy, and misidentification of twitching as nerve stimulation.

    Sonographic Resolution

    • Axial Resolution: Clarity along the axis of the ultrasound beam, dependent on pulse wavelength and cycle count.
    • Lateral Resolution: Clarity between adjacent structures visualized simultaneously, improving with increasing wave frequency and decreasing ultrasound beam width.
    • Temporal Resolution: Clarity of dynamic structures like pulsating vessels, improving with increased ultrasound frame rate.

    Improving Visualization Under Ultrasound

    • Probe Selection: High frequency for superficial structures, medium frequency for medium-depth structures, and low frequency for deep structures.
    • Depth Adjustment: Ensure appropriate depth setting for target nerve location.
    • Probe Orientation: Confirm probe orientation.
    • Gel Application: Apply sufficient gel.
    • Gain and Time-Gain Compensation Adjustment: Optimize image quality by reducing artifact.
    • Doppler Ultrasound: Identifies pulsating blood vessels and local anesthetic spread during injection.

    Paravertebral Space Boundaries

    • Posterior: Superior costotransverse ligament.
    • Anterolateral: Parietal pleura.
    • Medial: Vertebral bodies and intervertebral disks.
    • Contents: Thoracic spinal nerves and sympathetic trunk.

    Muscles of the Anterolateral Abdomen

    • Superficial to Deep: External oblique, internal oblique, and transverse abdominis muscles.
    • Innervation: Anterior rami of T7–L1.
    • Blocks Targeting This Area: Transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks.

    Brachial Plexus Formation and Subdivisions

    • Formation: C5–T1 nerve roots.
    • Subdivisions: Roots, trunks, divisions, cords, and branches.
    • Blocks Targeting This Area: Interscalene, supraclavicular, and infraclavicular brachial plexus nerve blocks, axillary, and various forearm nerve blocks.

    Lumbar Plexus Formation and Branches

    • Formation: T12–L4 nerve roots.
    • Branches: Ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Blocks Targeting This Area: Lumbar plexus, femoral, and fascia iliaca blocks.

    Sciatic Nerve Innervation and Approaches

    • Innervation: Majority of the lower extremity, excluding the anterior thigh and medial calf (innervated by lumbar plexus).
    • Formation: L4–S3 nerve roots.
    • Branches: Tibial and common peroneal nerves.
    • Approaches: Proximal (anterior, transgluteal, subgluteal) or at the popliteal fossa. Branches can also be blocked at the ankle.

    Cutaneous Innervation of the Ankle

    • Nerves: Tibial, saphenous, deep peroneal, superficial peroneal, and sural nerves.
    • Origin: Tibial, deep peroneal, superficial peroneal, and sural nerves arise from the sciatic nerve; saphenous nerve arises from the femoral nerve.
    • Distribution:
      • Tibial nerve: Heel and plantar surface of the foot.
      • Saphenous nerve: Medial aspect of the lower leg and ankle.
      • Superficial peroneal nerve: Dorsum of the foot.
      • Deep peroneal nerve: Webspace between the great and second toes.
      • Sural nerve: Lateral ankle.

    Complications of Regional Anesthesia

    • General: Bleeding, infection, intravascular or intraneural injection (leading to LAST or nerve damage), allergic reactions, damage to adjacent structures, and block failure.
    • Specific to Interscalene and Supraclavicular Blocks: Phrenic nerve involvement (ipsilateral diaphragmatic paresis), sympathetic chain involvement (ipsilateral Horner syndrome), recurrent laryngeal nerve involvement (hoarseness).
    • Other Complications: Subarachnoid or epidural injection, pneumothorax.

    Decreasing the Risk of Complications

    • Sterile Technique: Essential.
    • Patient Monitoring: Appropriate monitoring essential.
    • Local Anesthetic Injection Technique: Small increments (≤ 5 cc, at a rate of no more than 1 cc/s) with aspiration before each injection.
    • Circulation Time Monitoring: Allow one full circulation time (15–30 seconds) after injecting 10 cc to assess for systemic toxicity signs.
    • Needle Withdrawal: Stop injecting and withdraw the needle slightly if the patient experiences sharp pain or paresthesias.
    • Ultrasound Guided Blocks: Only advance needle if the tip is visualized.
    • Nerve Stimulator Blocks: Avoid local anesthetic injection if twitch response is obtained below 0.3 mA.
    • Continuous Patient Monitoring: For changes in hemodynamics or mental status.

    Commonly Used Local Anesthetics

    • Short-acting: 2-Chloroprocaine (1.5 to 2 hours duration); rapid metabolism by plasma cholinesterases.
    • Intermediate-acting: Lidocaine (1–3 hours), mepivacaine (3–5 hours).
    • Long-acting: Ropivacaine (6–24 hours), bupivacaine (6–30 hours); slower onset, higher cardiotoxicity with bupivacaine compared to ropivacaine.

    Local Anesthetic Additives

    • Vasoconstrictors: Epinephrine (extends duration, decreases systemic absorption, presence indicates intravascular injection).
    • Sodium Bicarbonate: Alkalinizes local anesthetic solution, decreasing time to block onset.
    • Clonidine: Alpha-2 agonist with analgesic properties, potentially improving block quality and prolonging duration.
    • Dexamethasone and Dexmedetomidine: Thought to prolong block duration.

    Factors Influencing Local Anesthetic Onset and Duration

    • Onset: Dependent on pKa (closer to body’s pH, quicker the onset).
    • Duration: Type of local anesthetic, presence/absence of vasoconstrictor, lipid solubility, and protein binding.

    LAST (Local Anesthetic Systemic Toxicity)

    • Cause: Perineural injection of large doses of local anesthetic, or accidental intravascular, intrathecal, or epidural injection.
    • Symptoms: CNS effects (excitatory phase: tinnitus, circumoral numbness, lightheadedness, altered mental status, tremors, and tonic-clonic seizures; depressive phase: respiratory depression, coma, respiratory arrest) and cardiovascular effects (hypotension, conduction disturbances, ventricular arrhythmias, and direct myocardial depression).

    Treatment of LAST

    • Manage symptoms and complications according to the severity.
    • Provide supportive care, including airway management, oxygen, and cardiovascular support.
    • Consider medications like benzodiazepines for seizures, lipid emulsion for cardiac arrest, and anticonvulsants for long-term seizure control.

    Local Anesthetic Systemic Toxicity (LAST) Treatment Algorithm

    • Immediately discontinue administration of all local anesthetics.
    • Alert cardiopulmonary bypass team.
    • Ventilate with 100% oxygen, placing advanced airway if necessary.
    • Treat seizures with benzodiazepines.
    • Promptly consider lipid emulsion therapy at the first sign of a severe LAST event.
    • Propofol is not an adequate alternative to lipid emulsion therapy.
    • Treat hypotension and bradycardia.
    • Start cardiopulmonary resuscitation if the patient becomes pulseless.
    • Continue monitoring for 4 to 6 hours after a cardiovascular event, or at least 2 hours after a limited CNS event.
    • Reduce epinephrine boluses to 1 mcg/kg (or lower).
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers.

    Intravenous Lipid Emulsion Dosing for LAST

    • Patients weighing more than 70 kg should receive a 100 mL lipid emulsion 20% bolus over 2 to 3 minutes.
    • This should be followed by an infusion of 200 to 250 mL over 15 to 20 minutes.
    • Patients weighing less than 70 kg should receive a 1.5 mL/kg bolus, followed by an infusion of 0.25 mL/kg/min ideal body weight.
    • If the patient remains unstable after initial treatment, repeat the bolus at the same dose 1 to 2 times and double the infusion rate.
    • The maximum dose of lipid emulsion should not exceed 12 mL/kg.

    Benefits of Regional Anesthesia

    • Regional anesthesia is beneficial for patients in whom general anesthesia should be avoided.
    • This includes patients with:
      • Severe cardiopulmonary disease.
      • Obstructive sleep apnea.
      • Postoperative nausea and vomiting.
      • Chronic pain.
      • Substance abuse.

    Methods of Delivering Regional Anesthesia

    • Peripheral nerve single injections or catheters.
    • Intravenous (IV) regional techniques.
    • Neuraxial blockade.

    Locating Peripheral Nerves

    • Ultrasound.
    • Nerve stimulator.
    • Elicited paresthesias.
    • Landmark techniques.

    Complications of Nerve Blocks

    • Bleeding.
    • Infection.
    • Intravascular or intraneural injection.
    • Allergic reactions.
    • Local anesthetic systemic toxicity (LAST).
    • Damage to adjacent structures.

    Indications for Peripheral Nerve Blocks

    • Anesthesia:
      • Allows patients to avoid general anesthesia.
      • May allow for avoiding periprocedural pain medication.
      • Helpful for patients with risk factors such as difficult airway or intolerance to general anesthesia.
    • Analgesia:
      • Avoid postoperative opioids and their associated side effects.
      • Improves postoperative pain scores.
      • Increases patient satisfaction.
      • Decreases nausea.
      • Decreases the likelihood of postoperative admission for pain control.

    Contraindications for Peripheral Nerve Blocks

    • Anticoagulation - increased risk of hematoma formation and subsequent nerve damage.
    • Peripheral neuropathy - e.g., symptomatic spinal stenosis or Guillain-Barré syndrome.
    • Traumatic injury - successful nerve blocks can mask diagnosis of a compartment syndrome, delaying treatment.
    • Systemic infection - placement of a nerve catheter can result in a perineural abscess.

    Common Nerve Blocks of the Upper Extremity

    • Interscalene.
    • Supraclavicular.
    • Infraclavicular.
    • Axillary.
    • Individualized radial, median, and ulnar nerve blocks.

    Choosing the Most Suitable Brachial Plexus Block

    • Interscalene: Procedures on the shoulder, distal clavicle, and proximal humerus.
    • Supraclavicular: Procedures below the shoulder, approximately 50% chance of phrenic nerve blockade, increased risk of pneumothorax, ultrasound guidance advised.
    • Infraclavicular: Procedures from the mid-humerus to the fingers, technically challenging as it requires a steep approach.
    • Axillary: Procedures from the mid-humerus to the fingers, frequently spares the musculocutaneous nerve requiring it to be blocked separately, requires patient to abduct the arm.

    Anatomical Landmarks and Techniques for Brachial Plexus Blocks

    • Supraclavicular:
      • Performed in the semi-sitting position.
      • Head turned to the opposite side.
      • Reach arm to ipsilateral lower extremity and externally rotate shoulder to depress clavicle and increase space.
      • Needle advanced from lateral to medial.
      • Local anesthetic deposited surrounding divisions of the brachial plexus, lateral to the subclavian artery.
      • Be cautious to avoid any traversing arteries as anatomy varies widely in the supraclavicular region.
    • Infraclavicular:
      • Deep block (benefits include avoiding phrenic nerve paralysis & accommodation of peripheral nerve catheters).
      • Patient is positioned supine with arm either at the patient's side or above the head.
      • Probe oriented cephalad to caudad at the level of the coracoid process.
      • Needle advanced to 6 o'clock position of the axillary artery.
      • Local anesthetic deposited to cover all three cords of the brachial plexus with one injection.
      • Achieve U-shaped spread to both sides of the artery.
    • Axillary:
      • Patient's arm abducted to 90 degrees.
      • Transducer placed along the medial aspect of the arm in the axilla.
      • Needle traversed from cephalad to caudad, ending at the 6 o'clock position of the axillary artery.
      • Multiple injections often required to achieve circumferential spread to anesthetize the median, ulnar, and radial nerves.
      • A separate injection may be required to anesthetize the musculocutaneous nerve to ensure adequate distal forearm coverage.

    Specific Risks of Brachial Plexus Blocks

    • Supraclavicular:
      • Increased risk of pneumothorax compared to infraclavicular and axillary approach.
      • Risk of intravascular injection, especially in the subclavian artery and dorsal scapular and suprascapular arteries.
    • Infraclavicular:
      • Increased risk of intravascular injection.
      • More challenging to visualize the needle due to depth & steep angle of insertion, making aspiration before every injection important.
      • Difficult to visualize small arteries and veins at lower depths.
    • Axillary:
      • Thought to carry the least amount of risk compared to other brachial plexus blocks.
      • If there is an arterial puncture, the axillary artery is compressible due to superficial location, making manual compression viable for preventing hematoma formation.

    Ulnar Nerve Sparing During Supraclavicular Block

    • If motor block of the arm occurs but patient can still feel pain in one finger, there is likely ulnar nerve sparing.
    • This is likely due to inadequate block of the lower trunk.
    • This occurs because of a deficiency of local anesthetic in the "corner pocket" where the lower trunk is nestled between the first rib and the subclavian artery.
    • Options for addressing this include:
      • Performing a supplementary rescue block to anesthetize the "corner pocket".
      • Blocking the ulnar nerve more distally.

    Common Nerve Blocks of the Lower Extremity

    • Nerves originate from the:

      • Lumbar plexus (L1-L5).
      • Sacral plexus (L4-S3).

    • Often referred to as the lumbosacral plexus.

    • Lumbar plexus blocks: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.

      • Most common: Lumbar plexus, femoral, and saphenous nerve blocks.

    • Sacral plexus blocks: sciatic, superior and inferior gluteal, pudendal, and posterior cutaneous nerve of the thigh.

      • Most common: transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.

    Choosing the Most Suitable Nerve Block for Lower Extremity Procedures

    • Consider:
      • Location of surgery
      • Possible application of a tourniquet
      • Need for postoperative motor function
    • A combination of sciatic and femoral blocks are needed for complete surgical anesthesia of the lower extremity.
    • Ankle block is effective for surgery on the toes and forefoot but not the hindfoot.

    Anatomical Landmarks and Techniques of Lower Extremity Blocks

    • Lumbar plexus:
      • Deep block.
      • Needle insertion point: 4 to 5 cm lateral to the L4-L5 interspace (approximated by the top of the iliac crest).
      • Typically performed with nerve stimulator guidance.
      • Located in the body of the psoas major muscle, 2 cm deep to the transverse process of the lumbar spine.
      • Depth of needle insertion usually between 6-8 cm.
    • Femoral nerve:
      • Block for anesthesia of the anterolateral thigh and the medial skin below the knee.
      • Nerve can be visualized with ultrasound 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle.
    • Saphenous nerve:
      • Largest cutaneous branch of the femoral nerve.
      • Located more distally in the lower extremity.
      • Often blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • Sciatic nerve:
      • Found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur.
      • Subgluteal approach is less technically challenging.
      • Popliteal region: Sciatic nerve branches into common peroneal and tibial nerves.
      • Found posterior to the femur and posterolateral to the popliteal artery.
      • Muscle borders include the semitendinosus and semimembranosus medially and the biceps femoris laterally.

    Specific Risks of Nerve Blocks to the Lower Extremity

    • Nerve injury:
      • Rare, not fully understood.
      • Preexisting neuropathy increases risk of nerve damage from intraneural injection, ischemia, or local anesthetic toxicity.
    • Intravascular injection.
    • Infection.
    • Damage to surrounding structures.
    • Lumbar plexus block:
      • Increased risk due to depth and proximity to vulnerable structures.
      • Complications reported: aortic perforation with retroperitoneal hematoma, intrathecal injection, and bowel perforation.

    Plane Block vs. Peripheral Nerve Block

    • Plane block:
      • Local anesthetic infiltration into a fascial plane where various nerves traverse.
      • No distinct nerve needs to be identified.
      • Examples: TAP block, erector spinae block.
      • Requires higher volume of local anesthetic.
      • Reduced risk of direct nerve damage from needle because nerves are small or not present at the injection site.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    • Thoracic paravertebral block:
      • Local anesthetic deposited in the paravertebral space where the thoracic spinal nerves and sympathetic trunk reside.
      • Results in three to seven dermatomes of unilateral anesthesia to the abdomen or chest wall surrounding the insertion point.
      • Good choice for smaller thoracic, abdominal, or breast surgeries.
    • Transversus abdominis plane (TAP) block:
      • Indicated for lower abdominal surgeries such as hysterectomy or hernia repair.
      • Local anesthetic deposited in the fascial plane between the internal oblique and transversus abdominis muscles.
      • Anterior divisions of T10-L1 and the ilihypogastric and ilioinguinal nerves lie in this plane.
      • Unilateral anesthesia of the lower anterior abdominal wall, including the groin.
      • Subcostal TAP approach can be used for upper abdomen.
      • Bilateral blocks can be used for midline surgeries.

    Novel Truncal Nerve Blocks

    • Erector spinae block:
      • Between transverse process of vertebra and the erector spinae muscles.
      • Blocks thoracic/lumbar spinal nerves.
      • Breast, chest, upper and lower abdominal surgery depending on injection point.
    • PECS I block:
      • Between pectoralis major and pectoralis minor.
      • Blocks the lateral and medial pectoral nerves.
      • Partial coverage for breast surgery.
    • PECS II block:
      • Between pectoralis minor and serratus anterior.
      • Blocks thoracic intercostal nerves and long thoracic nerve.
      • Breast surgery including axillary dissection.
    • Serratus anterior block:
      • Deep to the serratus anterior muscle.
      • Blocks thoracic intercostal nerves, thoracodorsal, and long thoracic nerves.
      • Procedures of the hemi-thorax, including breast and thoracic surgery.
    • Quadratus lumborum block:
      • Anterolateral border of the quadratus lumborum muscle.
      • Blocks thoracic/lumbar spinal nerves.
      • Upper or lower abdominal surgeries.

    Specific Risks of Common Truncal Nerve Blocks

    • Paravertebral block:
      • Additional risk of pneumothorax due to proximity to the pleura.
      • Epidural spread can occur, leading to unintended contralateral effects and hemodynamic changes.
      • Vagal reaction is common.
    • TAP block:
      • Rare serious complications possible, such as intraperitoneal injection and possible injury to abdominal viscera.

    Advantages and Disadvantages of Truncal Blocks

    • Paravertebral block:
      • Versatile, applicable to nearly any truncal procedure.
      • Relatively dense analgesia, often effective for surgical anesthesia.
      • Higher risk than newer truncal blocks.
    • PECS or serratus anterior block:
      • Easier to perform than paravertebral block.
      • Equivalent analgesia with lower potential risk.
      • PECS blocks block the pectoral nerves which are spared by other techniques.
    • TAP or quadratus lumborum block:
      • Easier to perform than paravertebral block.
      • Lower risk.
      • Quadratus lumborum block covers more dermatomes per injection relative to TAP block.
      • Quadratus lumborum block cannot be performed in the supine position and is more challenging than the TAP block.
    • Erector spinae block:
      • Can be used for the same indications as the paravertebral block.
      • Lower risk of direct injury or nerve-threatening hematoma due to location.
      • Disadvantages: benefits are not well described in the literature and it likely delivers less effective analgesia than the paravertebral block.

    Nerve Blocks

    • Most upper extremity nerve blocks involve blocking the brachial plexus
    • The nerves of the lower extremity are derived from the lumbar plexus (L1–L5) and the sacral plexus (L4–S3)
    • The lumbar plexus gives rise to iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves
    • The sacral plexus gives rise to the sciatic nerve, as well as the superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh
    • The most common lumbar plexus nerve blocks are the lumbar plexus, femoral, and saphenous
    • The most common sacral plexus nerve blocks are the transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks

    Neuraxial Anesthesia

    • Neuraxial anesthesia refers to injection of anesthetics or analgesics into the epidural or intrathecal space
    • Epidural anesthesia refers to injection of anesthetics or analgesics into the epidural space at either the lumbar or thoracic level
    • Caudal anesthesia refers to injection into the sacral hiatus
    • Spinal anesthesia, spinal block, subarachnoid block, and intrathecal block are all terms used to describe injection into the intrathecal space

    Analgesia VS Anesthesia

    • Anesthesia implies a complete sensory and motor blockade, while analgesia implies only sensory blockade
    • Analgesia may be achieved with dilute local anesthetic, epidural opioids, or a combination of the two

    Advantages of Neuraxial Anesthesia

    • Reduced metabolic stress response to surgery and anesthesia
    • Significant blood loss reduction by comparison with general anesthesia
    • Decreased incidence of venous thromboembolic complications
    • Reduced pulmonary compromise
    • Airway manipulation and loss of airway protection are usually avoided
    • Mental status remains intact
    • Total systemic dose of drug(s) is markedly decreased
    • Motor blockade from spinal avoids the need for muscle relaxant medications
    • Markedly lower incidence of anesthesia-induced postoperative nausea and vomiting
    • Markedly improved pain control with minimal or no systemic opioids

    Spinal vs Epidural

    • A spinal anesthetic is performed by puncturing the dura and injecting a small amount of local anesthetic directly into the cerebrospinal fluid (CSF)
    • An epidural anesthetic requires a 10-fold increase in dose of local anesthetic to fill the epidural space and penetrate the nerve coverings
    • Spinal anesthetics produce a rapid, dense, and predictable neural blockade
    • Epidural anesthesia involves a slower onset and often less dense blockade, and the anesthesia produced tends to be segmental

    Advantages of Spinal Anesthesia

    • Quicker onset time from injection to adequate surgical blockade
    • More predictable block density, particularly regarding motor blockade
    • Less risk for block “patchiness” and/or unilateral block
    • Lower volume of local anesthesia required, essentially eliminating the risk of local anesthetic systemic toxicity (LAST)

    Disadvantages of Spinal Anesthesia

    • More immediate and dramatic hemodynamic changes often observed
    • Not easily titratable
    • No ability to provide continued neuraxial analgesia beyond initial dose
    • No ability to augment intensity or increase duration of blockade if inadequate
    • Block level or dermatomal window cannot be augmented or modified once set

    Assessment Before Neuraxial Anesthesia

    • History: previous back injury or surgery, neurological symptoms, bleeding tendencies, anticoagulation or antiplatelet medication, prior regional anesthesia
    • Physical examination: brief neurological examination for strength and sensation, back examination for landmarks and potential anatomic abnormalities, cardiovascular examination
    • Surgery specific: expected duration, expected blood loss, positioning required, need for muscle relaxation, surgeon's preferences
    • Patient education: detailed explanation of the procedure, risks, benefits, and options

    Epidural Space

    • The epidural space lies just outside and envelops the dural sac containing the spinal cord and CSF
    • The epidural space has its widest point (5 mm) at L2
    • The epidural space contains fat, lymphatics, and an extensive venous plexus (Batson plexus)
    • The epidural space wraps 360 degrees around the dural membrane

    Lumbar Epidural Anesthetic Technique

    • The patient may be sitting or lying laterally
    • Visualize a line between the iliac crests to locate the L4 spinous process
    • Palpate the L2–L3, L3–L4, and L4–L5 interspaces
    • The anesthesiologist/provider must wear a hat, mask, sterile gloves and remove all jewelry
    • The site should be prepped/draped
    • A skin wheal is made with local anesthetic at the desired insertion site
    • Once initial resistance from ligaments is felt, remove the needle stylet and attach a syringe with 3 to 4 mL of air or saline
    • Advance several millimeters at a time, tapping the syringe intermittently
    • As the needle passes through ligamentum flavum and enters the epidural space, there is often a pop or give, and the air or fluid in the syringe injects easily
    • Thread the catheter about 5 cm into the epidural space
    • After attaching the injector port to the catheter, it is aspired for blood or CSF; if negative, a test dose may be given

    Paramedian Epidural Placement

    • Identify the spinous process at the desired interspace level and use local anesthetic to create a skin wheal 1 to 2 fingerbreadths lateral
    • Insert the epidural needle through the wheal perpendicular to the patient's skin, until the transverse process of the vertebra is encountered
    • Walk the epidural needle off the transverse process, moving superiorly and medially, until the needle is engaged in the ligamentum flavum
    • Attach a friction-free syringe and advance until loss of resistance is achieved
    • This approach is useful at high thoracic levels, where the spinous processes are acutely angled downward

    Caudal Anesthesia

    • Caudal anesthesia is a form of epidural anesthesia in which the injection is made at the sacral hiatus (S5)
    • Caudal anesthesia is used primarily in children to provide postoperative analgesia after herniorrhaphy or perineal procedures

    Combined Spinal-Epidural Anesthetic (CSE)

    • A dural-puncture epidural (DPE) is performed by passing a long spinal needle through an epidural needle that has been placed into the epidural space
    • A combined spinal-epidural (CSE) is the same technique, but additionally when CSF is confirmed in the spinal needle, a dose of local anesthetic with or without adjuvants (e.g., small dose of opioid) is deposited in the subarachnoid space
    • Either technique combines the advantages of both spinal and epidural anesthesia and both techniques result in a more reliable epidural catheter

    Physiological Changes After Neuraxial Anesthesia

    • Decrease in blood pressure
    • Changes in heart rate: tachycardia or bradycardia
    • Ventilatory changes: patients may become subjectively dyspneic
    • Bladder distention
    • Change in thermoregulation
    • Neuroendocrine changes: neural blockade above T8 blocks sympathetic afferents to the adrenal medulla, inhibiting the neural component of the stress response

    Local Anesthetics Used in Epidural Anesthesia for Surgical Procedures

    • Chloroprocaine: rapid onset, least toxic, intense sensory and motor block
    • Lidocaine: immediate onset, intense sensory and motor block
    • Bupivacaine: most cardiotoxic; motor < sensory block
    • Ropivacaine: less cardiotoxic than bupivacaine; most expensive

    Anatomic Structures Trespassed During Intrathecal Injection

    • From superficial to deep, the structures include: skin, subcutaneous/adipose tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, dura mater, and arachnoid membrane

    Bony Structures Encountered During Intrathecal Injection

    • Shallow osseous tissue is likely spinous process
    • Deep osseous tissue tends to be vertebral lamina

    Principal Sites of Effect of Spinal Local Anesthetics

    • Sodium channels in the spinal nerve roots and the spinal cord itself

    Termination of Effect of Spinal Anesthesia

    • Dissociation of the local anesthetic from nerve sodium channels and resorption of the agent from the CSF into the systemic circulation limits duration

    Factors Involved in Distribution of Spinal Blockade

    • Patient characteristics: height, position, intraabdominal pressure, anatomic configuration of the spinal canal, and pregnancy
    • Total injected milligram dose (not the volume or concentration) of local anesthetic
    • The baricity of the local anesthetic solution
    • Patient position during and after intrathecal injection and vertebral column curvature

    Levels for Spinal Anesthesia

    • The selected level should be below L1 in an adult, and L3 in a child, to avoid needle trauma to the spinal cord

    Common Complication of Neuraxial Anesthesia

    • Hypotension
    • Bradycardia

    Neuraxial Anesthesia Complications

    • Hypotension is common and often secondary to sympatholysis

      • Causes include: hypovolemia, advanced age, high sensory level, low baseline systolic blood pressure, and block level at or above L3-L4
      • Treatment includes vasopressor infusion (e.g., phenylephrine)
      • Fluid pre-loading does not reliably prevent hypotension and should be used cautiously in high-risk patients.
      • Trendelenburg positioning shortly after intrathecal injection should be used with caution as it can increase the level of blockade with hyperbaric spinal anesthesia.

    • Bradycardia can be caused by unopposed vagal tone from high sympathectomy, cardioaccelerator fiber blockade (T1-T4), or Bezold-Jarisch or reverse Bainbridge reflexes.

      • Patients with increased baseline vagal tone are at higher risk.

    • Post-dural Puncture Headache (PDPH) is a common complication that can be treated with epidural blood patch (EBP).

    • Transient Neurological Syndrome (TNS) is associated with spinal lidocaine and presents with pain or dysesthesias in the buttocks, radiating to the thighs and calves.

      • Symptoms usually improve with activity, worsen at night, and respond to NSAIDs.
      • It typically resolves within a week.

    Neuraxial Anesthesia & Anticoagulation

    • LMWH (e.g., enoxaparin) should be discontinued at least 12 hours before neuraxial procedures for prophylactic doses and 24 hours for other dosing regimens.
    • Heparin should be discontinued 24 hours before neuraxial procedures for doses > 20,000 units/day. Wait for PTT normalization (4-6 hours) before procedures for lower doses.

    Neuraxial Opioids

    • Provide intense visceral analgesia and can prolong sensory blockade without affecting motor or sympathetic function.
    • Lipophilic opioids (fentanyl, sufentanil) have a more localized effect compared to hydrophilic opioids (morphine).
    • Side effects include respiratory depression, nausea, vomiting, pruritus, and urinary retention.
    • Lower total opioid dose required compared to systemic administration for equivalent analgesia.

    Choosing the Right Local Anesthetic

    • Factors to consider include onset, duration, safety profile, patient characteristics, and surgical procedure.
    • Bupivacaine is a good option for ambulatory procedures, but higher doses may delay voiding and discharge.
    • Lidocaine is commonly used for obstetric procedures due to its lower risk of TNS and improved time to discharge.

    Epinephrine in Local Anesthetic Solutions

    • Benefits include reduced local anesthetic uptake, improved analgesia, and identification of intravascular injection.
    • Considerations include potential risks in patients with severe coronary disease.

    Epidural Anesthesia

    • The degree of motor block can be decreased by lowering local anesthetic concentration, using agents with favorable sensory:motor dissociation, and adjusting infusion rate.
    • Bupivacaine and ropivacaine provide less motor block for a given amount of sensory block (sensory:motor dissociation).

    Level of Anesthesia for Surgical Procedures

    • It's crucial to understand the innervation of the structures involved in the surgery.
    • Sensory level should be tested prior to incision.

    Segmental Block

    • Epidural anesthesia is segmental, with the most intense block near the catheter insertion site.
    • Place the catheter as close to the surgical site as possible.

    Other Indications for Neuraxial Anesthesia

    • Pain management for rib fractures, vascular access procedures, high spinal cord injury patients.
    • May allow for earlier recognition of complications in high-risk procedures.

    Epidural Anesthesia Dosage and Spread

    • Volume of local anesthetic is the primary determinant of the extent of the blockade.
    • Other factors include age, pregnancy, obesity, height, and spinal anatomy.

    Continuous Spinal Anesthesia

    • Safe and effective using larger gauge needles and catheters.
    • Lower incidence of hypotension compared to traditional spinal anesthesia.
    • Allows for titration of local anesthetics.

    Neuraxial Anesthesia and Enhanced Recovery After Surgery (ERAS) Protocols

    • ERAS protocols promote multimodal analgesia and reduced systemic opioid use.
    • Neuraxial analgesia often eliminates the need for systemic opioids.

    Postoperative Assessment After Neuraxial Anesthesia

    • Assess patient satisfaction, sensory and motor block regression, back pain, headache, pain control, and side effects.
    • Thorough neurological evaluation is necessary for any residual block or neurological complaints.
    • Rule out pathology in the epidural space if necessary.

    Key Points: Neuraxial Anesthesia

    • Neuraxial anesthesia can increase sensitivity to other sedative medications.
    • Patients require close monitoring and potentially aggressive fluid resuscitation and vasopressor support.
    • PDPH is a common complication and EBP is the gold standard treatment.
    • TNS is associated with lidocaine spinal anesthesia and presents with pain in the buttocks and dorsal lower extremities.
    • Epidural anesthesia is segmental with the most intense block near the catheter insertion site.
    • ERAS protocols emphasize the use of regional anesthesia, including neuraxial techniques.

    Peripheral Nerve Blocks

    • Common indications include anesthesia or analgesia.
    • Can help avoid general anesthesia and postoperative opioids.

    Contraindications for Peripheral Nerve Blocks

    • Anticoagulation increases the risk of hematoma formation and subsequent nerve damage.
    • Peripheral neuropathy can also increase the risk.
    • Successful nerve block after traumatic injury can mask compartment syndrome.
    • Systemic infection can lead to perineural abscess formation.

    Common Upper Extremity Nerve Blocks

    • Brachial plexus blocks are commonly performed at different anatomical locations: interscalene, supraclavicular, infraclavicular, and axillary.
    • Supraclavicular block is the mainstay for procedures below the shoulder.
    • Individualized radial, median, and ulnar nerve blocks can be performed under ultrasound guidance.

    Choosing the Appropriate Brachial Plexus Block

    • Interscalene block is suitable for procedures involving the shoulder, distal clavicle, and proximal humerus.
    • Supraclavicular, Infraclavicular, and Axillary blocks are detailed in Table 69.1 in the original text.

    Brachial Plexus Nerve Blocks

    • Supraclavicular block anesthetizes from below the deltoid to the fingers.
    • Infraclavicular block anesthetizes from the mid-humerus to the fingers.
    • Axillary block anesthetizes from the mid-humerus to the fingers but frequently spares the musculocutaneous nerve.
    • Supraclavicular block has a higher risk of pneumothorax due to its proximity to the pleura.
    • Ultrasound guidance is advised when performing a supraclavicular block to minimize the risk of pneumothorax.
    • Infraclavicular blocks have a higher risk of intravascular injection due to the steep angle of needle insertion and the difficulty visualizing the needle tip.
    • The axillary block is considered the least risky brachial plexus block due to the compressibility of the axillary artery, making manual compression a viable technique to prevent hematoma.
    • A supplementary rescue block can be performed to anesthetize the "corner pocket" when a supraclavicular nerve block results in a motor block of the arm, but the patient can still feel pain in one finger.
    • The ulnar nerve can be blocked more distally if the "corner pocket" is not adequately anesthetized.

    Lower Extremity Nerve Blocks

    • The iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves are derived from the lumbar plexus.
    • The lumbar plexus, femoral, and saphenous nerve blocks are most common.
    • The sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and posterior cutaneous nerve of the thigh are derived from the sacral plexus.
    • The transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks are most common.
    • A combination of sciatic and femoral blocks is required for complete surgical anesthesia of the lower extremity.
    • An ankle block is effective for surgery on the toes and forefoot, but the hindfoot is usually spared.
    • The lumbar plexus block is a deep block performed with nerve stimulator guidance.
    • Ultrasound guidance is recommended for femoral nerve blocks, where the nerve is located 1 cm lateral to the femoral artery.
    • The subgluteal approach to blocking the sciatic nerve is considered less technically challenging and easier to visualize using ultrasound.

    Truncal Nerve Blocks

    • Thoracic paravertebral blocks are indicated for smaller thoracic, abdominal, or breast surgeries, providing anesthesia to three to seven dermatomes.
    • Transversus abdominis plane (TAP) blocks are used for lower abdominal surgeries, providing unilateral anesthesia of the lower anterior abdominal wall.
    • The upper abdomen can also be blocked using the subcostal TAP approach.
    • The erector spinae, PECS, serratus anterior, and quadratus lumborum blocks are newer truncal block techniques that are gaining popularity.
    • Paravertebral blocks have an increased risk of pneumothorax and epidural spread.
    • TAP blocks carry a risk of intraperitoneal injection and possible injury to abdominal viscera.
    • PECS blocks are easier to perform than paravertebral blocks with equivalent analgesia and lower risk.
    • PECS blocks have the advantage of blocking the pectoral nerves, which are spared by other techniques.
    • The quadratus lumborum block covers more dermatomes per injection compared to the TAP block but is technically more challenging.
    • The erector spinae block is a low-risk alternative to the paravertebral block but may provide less effective analgesia.

    Key Points:

    • Nerve blocks are used for anesthesia or analgesia.
    • Brachial plexus blocks are named for their anatomic location for probe position or needle insertion.
    • The lumbar plexus and sacral plexus give rise to the nerves of the lower extremity.
    • Increased use of ultrasound has led to the development of novel truncal blocks.

    Indications and Contraindications for Regional Anesthesia

    • Peripheral nerve blocks can provide surgical anesthesia and/or intra- and postoperative analgesia for various surgeries.
    • Common surgeries performed with nerve blocks include orthopedic procedures, amputations, thoracotomies, laparotomies, arteriovenous fistula creations/revisions, and mastectomies.
    • Contraindications for peripheral nerve blocks include patient refusal, sepsis/bacteremia, infection at the injection site, preexisting neuropathy, and coagulopathy.

    Advantages and Disadvantages of Peripheral Nerve Blockade vs. General Anesthesia

    • Regional techniques are helpful when general anesthesia is undesirable, such as in patients with anticipated difficult airway or severe cardiopulmonary disease.
    • Opioid-sparing effects of nerve blocks are valuable for perioperative pain control in patients with obstructive sleep apnea, severe postoperative nausea and vomiting, chronic opioid therapy, opioid abuse history, or allergies to analgesics.
    • Local anesthetic injection can aid in perfusion of compromised flaps or extremities by causing vasodilation at the block site.
    • Procedures under regional blocks require patient cooperation, which might be unsuitable for children or patients with high anxiety, developmental delay, altered mental status, or dementia.
    • Inadequate sensory loss before surgical incision can be due to incomplete nerve block or insufficient time between block and incision.
    • Preoperative blocks lack flexibility for adjustments to surgical approach if intraoperative findings differ.
    • Regional blocks are frequently used in conjunction with general anesthesia rather than as the primary anesthetic technique.

    Methods of Regional Anesthesia

    • Peripheral nerve blocks can be administered as a single injection or via continuous infusion through a catheter.
    • Neuraxial blockade can be performed as an injection into the subarachnoid space (spinal anesthesia) or as a continuous infusion into the epidural space.
    • Intravenous regional anesthesia (Bier block): local anesthetic is injected into an extremity intravenously in the presence of an inflated tourniquet.

    Bier Block Technique

    • An IV is placed in the operative extremity.
    • After elevation and exsanguination of the limb, a double tourniquet is inflated, and lidocaine (≤ 3 mg/kg) is injected intravenously into the operative extremity.
    • The extremity is lowered, the IV is removed, and the surgical procedure can proceed.
    • Typically used for procedures lasting 30 to 45 minutes, as longer procedures are generally limited by tourniquet pain.

    Techniques for Performing Peripheral Nerve Blocks

    • Most peripheral nerve blocks use ultrasound guidance.
    • Nerve stimulation can be used alone or in conjunction with ultrasound.
    • Some blocks are performed using anatomic landmarks alone or via subcutaneous infiltration (field block).

    Ultrasound Guided Nerve Block Technique

    • Uses ultrasound images to guide needle advancement and local anesthetic injection around neural structures.
    • Can be performed using an in-plane (IP) or out-of-plane (OP) approach.
    • IP approach: needle advancement in the plane of the ultrasound beam, visualizing the entire needle shaft.
    • OP approach: needle advancement perpendicular to the ultrasound beam, visualizing only a needle cross section.
    • IP approach is generally preferred due to visualization of the entire needle trajectory and easier avoidance of important structures.
    • OP approach can be useful due to its shorter and more direct path to the nerve.
    • Advantages of using ultrasound: improved visualization of anatomic structures, decreased risk of complications like bleeding, hematoma formation, and pneumothorax, identification of anatomical variations, visualization of nerves ensuring complete anesthetic spread and no missed branches.
    • Disadvantage: specialized and expensive equipment may not be available in all locations.

    Nerve Stimulator Technique

    • A nerve stimulator device emits an electrical stimulus through an insulated block needle.
    • The stimulus is generally short (0.05–1 ms) and repetitive (1–2 Hz).
    • Needle advancement continues until muscle twitching and/or paresthesias, specific for the targeted nerve, are elicited.
    • Stimulus intensity is decreased until twitching or paresthesia disappears.
    • Continued response presence at low amplitudes signifies close proximity of the needle to the nerve.
    • Withdrawal of the needle slightly before injecting local anesthetic is recommended if response is still elicited at an intensity of 0.3 mA, indicating intraneural needle position.
    • Muscle twitching may not appear at all even with excellent needle positioning.
    • Advantages: confirmation of needle tip location.
    • Disadvantages: possibility of nerve trauma, inability to identify variant anatomy, potential misidentification of muscle stimulation as nerve stimulation.
    • Often used in conjunction with ultrasound, particularly helpful in cases of difficult ultrasound visualization.

    Sonographic Resolution

    • Axial resolution: relates to the number of planes along the ultrasound beam axis, dependent upon pulse wavelength and number of cycles per pulse.
    • Lateral resolution: describes the clarity between two adjacent structures visualized simultaneously, located the same distance from the probe.
    • Temporal resolution: relates to dynamic structures, such as pulsating vessels.

    Ways to Improve Ultrasound Visualization

    • Select an ultrasound scan head of appropriate frequency: high frequency for superficial structures, medium frequency for medium-depth structures, low frequency for deep structures.
    • Ensure the ultrasound picture is set to an appropriate depth to locate the target nerve.
    • Confirm the orientation of the probe and apply sufficient gel.
    • Adjust gain to change screen brightness and time-gain compensation to improve image quality by reducing artifacts.
    • Doppler ultrasound can be used to identify pulsating blood vessels or local anesthetic spread during injection.
    • Ensure the needle alignment with the ultrasound beam for IP needle visualization.
    • Do not advance the needle until the tip is clearly visualized.
    • Changing the tilt of the ultrasound probe can aid in visualizing the needle.
    • Echogenic needles are easier to visualize.

    Boundaries of the Paravertebral Space

    • Posterior border: superior costotransverse ligament.
    • Anterolateral border: parietal pleura.
    • Medial border: vertebral bodies and intervertebral disks.
    • Structures it houses: thoracic spinal nerves and sympathetic trunk.

    Muscles of the Anterolateral Abdomen

    • Superficial to deep: external oblique, internal oblique, transverse abdominis.
    • Innervation: anterior rami of T7–L1.
    • Blocks targeting this area: transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks.

    Brachial Plexus

    • Formed from the C5–T1 nerve roots.
    • Subdivisions: roots (C5–T1), trunks (upper, middle, and lower), divisions (anterior and posterior), cords (posterior, medial, and lateral), and branches (median, ulnar, radial, musculocutaneous, and axillary nerves).
    • Blocks targeting this area: interscalene, supraclavicular, infraclavicular brachial plexus nerve blocks, axillary, and various forearm nerve blocks.

    Lumbar Plexus

    • Formed from the T12–L4 nerve roots.
    • Branches: ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Blocks targeting this area: lumbar plexus, femoral, and fascia iliaca blocks.

    Sciatic Nerve

    • Innervates the lower extremity, excluding the anterior thigh and medial calf.
    • Arises from the L4–S3 nerve roots.
    • Branches: tibial and common peroneal nerves.
    • Blocking approaches: proximally (anterior, transgluteal, subgluteal), at the popliteal fossa, or branches at the ankle.

    Ankle Cutaneous Innervation

    • Innervated by five nerves: tibial, saphenous, deep peroneal, superficial peroneal, and sural.
    • Tibial nerve innervates the heel and plantar surface of the foot.
    • Saphenous nerve innervates the medial aspect of the lower leg and ankle.
    • Superficial peroneal nerve innervates most of the dorsum of the foot.
    • Deep peroneal nerve innervates a small area at the webspace between the great and second toes.
    • Sural nerve innervates the lateral ankle.

    Complications of Regional Anesthesia

    • Bleeding, infection, intravascular or intraneural injection (resulting in LAST or nerve damage, respectively), allergic reactions, damage to adjacent structures, and block failure.
    • Interscalene and supraclavicular blocks are associated with:
      • Phrenic nerve involvement: ipsilateral diaphragmatic paresis.
      • Sympathetic chain involvement: ipsilateral Horner syndrome.
      • Recurrent laryngeal nerve involvement: hoarseness.
    • Other potential complications: subarachnoid or epidural injection, pneumothorax.

    Minimizing Risk of Complications

    • Use sterile technique.
    • Ensure the patient is on appropriate monitors.
    • Inject local anesthetic in small increments (≤ 5 cc, at a rate of no more than 1 cc/s), aspirating before each injection.
    • Allow for one complete circulation time (about 15–30 seconds) after injecting 10 cc to assess for signs/symptoms of systemic toxicity.
    • Stop injecting and withdraw the needle slightly if the patient reports sharp pain or paresthesias.
    • Do not advance the needle unless the tip is visualized during ultrasound-guided blocks.
    • Do not inject local anesthetic if a twitch response is obtained below 0.3 mA during nerve stimulator blocks, indicating intraneural needle tip.
    • Continuously monitor patient closely for changes in hemodynamics or mental status.

    Local Anesthetics

    • Categorized by duration of action: short, intermediate, or long.
    • 2-Chloroprocaine: short-acting, lasting 1.5 to 2 hours, rapidly metabolized by plasma cholinesterases, allowing administration of high concentrations with minimal toxicity risk.
    • Intermediate-acting:
      • Lidocaine: 1–3 hours.
      • Mepivacaine: 3–5 hours.
      • Epinephrine is frequently added to lidocaine to extend the block duration.
    • Long-acting:
      • Ropivacaine: 6–24 hours.
      • Bupivacaine: 6–30 hours.
      • Bupivacaine has higher cardiotoxicity and causes more motor blockade than ropivacaine, but provides slightly longer duration.

    Additives to Local Anesthetics

    • Vasoconstrictors (epinephrine): prolong block duration, decrease systemic absorption, and indicate intravascular injection through tachycardia and hypertension effects.
    • Sodium bicarbonate: alkalinizes local anesthetic solution, decreasing time to block onset.
    • Clonidine: alpha-2 agonist with analgesic properties, improves block quality and prolongs duration.
    • Dexamethasone and dexmedetomidine: thought to prolong block duration.

    Factors Influencing Onset and Duration of Action

    • Onset of action: depends on pKa, a local anesthetic’s ionization constant. Closer pKa to the body’s pH, the quicker the onset.
    • Potency: correlates with lipid solubility. Higher lipid solubility requires lower concentrations to achieve same effect.
    • Duration of action: type of local anesthetic, presence/absence of vasoconstrictor, lipid solubility, and protein binding.

    LAST

    • Local anesthetic systemic toxicity (LAST) can result from perineural injection of large doses or accidental intravascular, intrathecal, or epidural injection.
    • CNS and cardiovascular systems are most affected.
    • CNS signs usually precede cardiovascular signs, but order might be reversed with rapid injection or bupivacaine use.
    • CNS disturbances: excitatory phase (tinnitus, circumoral numbness, lightheadedness, altered mental status, tremors, tonic-clonic seizures) followed by depressive phase (respiratory depression, coma, respiratory arrest).
    • Cardiovascular effects: hypotension, conduction disturbances, ventricular arrhythmias, direct myocardial depression, cardiac arrest.

    Treatment of LAST

    • Cardiac arrest in the setting of LAST is treated differently than cardiac arrest from other causes.

    Local Anesthetic Systemic Toxicity (LAST) Treatment

    • Discontinue all local anesthetic administration immediately
    • Call for help and a LAST rescue kit
    • Alert cardiopulmonary bypass team
    • Ventilate with 100% oxygen
    • Treat seizures with benzodiazepines
    • Consider lipid emulsion therapy promptly at the first sign of a severe LAST event
    • Treat hypotension and bradycardia
    • Start cardiopulmonary resuscitation if patient becomes pulseless
    • Continue monitoring 4 to 6 hours after a cardiovascular event or at least 2 hours after a limited CNS event
    • Epinephrine boluses should be reduced to 1 mcg/kg (or lower)
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers

    LAST Lipid Emulsion Therapy

    • Patients heavier than 70 kg should be administered 100 mL lipid emulsion 20% over 2 to 3 minutes, followed by an infusion of 200 to 250 mL over 15 to 20 minutes
    • Patients less than 70 kg should receive a 1.5 mL/kg bolus, followed by an infusion of 0.25 mL/kg/min ideal body weight
    • If the patient remains unstable after treatment, rebolus at the same dose and double the infusion rate

    Benefits of Regional Anesthesia

    • Patients avoid general anesthesia and periprocedural pain medication
    • Helpful for patients with risk factors like difficult airway or intolerance to general anesthesia
    • Analgesia blocks help avoid postoperative opioids and their associated side effects
    • Improves postoperative pain scores, increases patient satisfaction, decreases nausea, and decreases the likelihood a patient requires postoperative admission for pain control

    Peripheral Nerve Block Contraindications

    • Anticoagulation increases the risk of hematoma formation and subsequent nerve damage
    • Peripheral neuropathy, such as symptomatic spinal stenosis or Guillain-Barré, may increase the risk
    • A successful nerve block after a traumatic injury can mask a diagnosis of a compartment syndrome, delaying critical treatment
    • A systemic infection can result in a perineural abscess

    Upper Extremity Nerve Blocks

    • Most blocks involve the brachial plexus at different anatomic locations
    • Interscalene, supraclavicular, infraclavicular, and axillary are the most common brachial plexus blocks
    • Individualized blocks of the radial, median, and ulnar nerves can be performed to offer analgesia to the hand and fingers

    Choosing Brachial Plexus Blocks

    • The interscalene brachial plexus block is most suitable for procedures on the shoulder, distal clavicle, and proximal humerus
    • The supraclavicular block is effective for procedures below the shoulder
    • The infraclavicular block is a deep block avoiding phrenic nerve paralysis and accommodating peripheral nerve catheters
    • The axillary nerve block frequently spares the musculocutaneous nerve, requiring separate blocking

    Brachial Plexus Block Techniques

    • The supraclavicular nerve block is typically performed in the semi-sitting position with the head turned to the opposite side
    • The needle is advanced from lateral to medial and local anesthetic is deposited surrounding the divisions of the brachial plexus, lateral to the subclavian artery
    • The infraclavicular nerve block is performed with the patient supine and the arm positioned either at the patient’s side or above the head
    • The axillary nerve block is performed with the patient’s arm abducted to approximately 90 degrees
    • Multiple injections are often required for adequate spread

    Brachial Plexus Block Risks

    • The supraclavicular nerve block has an increased risk of pneumothorax compared to the infraclavicular and axillary approaches
    • The infraclavicular nerve block carries an increased risk of intravascular injection
    • The axillary nerve block is thought to have the least amount of risk comparatively

    Supraclavicular Nerve Block Complications

    • Ulnar nerve sparing from inadequate block of the lower trunk can occur
    • This can be addressed with a supplementary rescue block to anesthetize the “corner pocket”
    • Alternatively, the ulnar nerve can be blocked more distally

    Lower Extremity Nerve Blocks

    • The lower extremity requires multiple injections for complete coverage
    • The lumbar plexus gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves
    • The sacral plexus gives rise to the sciatic nerve, as well as the superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh

    Choosing Lower Extremity Nerve Blocks

    • Location of the surgery, possible application of a tourniquet, and need for postoperative motor function should all be considered with each block
    • For complete surgical anesthesia, a combination of sciatic and femoral blocks is often needed

    Lower Extremity Nerve Block Techniques

    • The lumbar plexus block is performed with nerve stimulator guidance, until contraction of the quadriceps muscle is elicited
    • The femoral nerve block is performed with ultrasound, visualising the nerve 1 cm lateral to the femoral artery
    • The saphenous nerve is often blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery
    • The proximal sciatic nerve is found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur

    Lower Extremity Nerve Block Risks

    • Risks include nerve injury, intravascular injection, infection, and damage to surrounding structures
    • Preexisting neuropathy places nerves at an increased risk for nerve damage from intraneural injection, ischemia, or toxicity from local anesthetics

    Plane Block vs Peripheral Nerve Block

    • A plane block involves anatomy where no distinct nerve needs to be identified
    • Plane blocks typically require a higher volume of local anesthetic to be effective
    • The risk of direct nerve damage from the needle is reduced because nerves are either small or not present at the location of injection

    Thoracic, Breast, and Abdominal Surgery Nerve Blocks

    • The paravertebral block involves depositing local anesthetic in the paravertebral space where the thoracic spinal nerves and sympathetic trunk reside
    • The transversus abdominis plane (TAP) block is indicated for lower abdominal surgeries
    • Bilateral blocks can be used for midline surgeries, keeping in mind limits of local anesthetic dosing to avoid toxicity

    Other Truncal Nerve Blocks

    • The erector spinae, PECS, serratus anterior, and quadratus lumborum blocks are novel blocks that are on the forefront of regional anesthesia
    • These blocks target the muscles and fascial planes where nerves are located to block a wider distribution of nerve innervation
    • This creates new options for blocking specific areas of the body for effective pain control

    Truncal Nerve Block Risks

    • Paravertebral blocks have risks related to the proximity of the pleura
    • Pleural puncture and injection, resulting in pneumothorax is possible
    • TAP blocks, rare serious complications are still possible, such as intraperitoneal injection and possible injury to abdominal viscera

    Truncal Nerve Block Advantages and Disadvantages

    • The paravertebral block is versatile in that it can be used for nearly any truncal procedure
    • It provides relatively dense analgesia that can often be effective for surgical anesthesia
    • However, its location makes it higher risk than other newer truncal blocks
    • For breast surgery, the PECS or serratus anterior blocks are easier to perform and provide equivalent analgesia with lower potential risk
    • The TAP and quadratus lumborum abdominal blocks are easier to perform than the paravertebral block and are lower risk
    • The erector spinae block can be used for the same indications as the paravertebral block but is lower risk for direct injury or nerve-threatening hematoma
    • The erector spinae block likely delivers less effective analgesia than the paravertebral block### Nerve Blocks
    • Upper extremity nerve blocks are often named based on their anatomic location.
    • Nerve blocks of the lower extremity are derived from the lumbar (L1-L5) and sacral (L4-S3) plexuses.
    • Common lumbar plexus blocks: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Common sacral plexus blocks: sciatic, superior and inferior gluteal, pudendal, and posterior cutaneous nerve of the thigh.
    • Ultrasound guidance has led to the development of novel truncal blocks.

    Neuraxial Anesthesia

    • Epidural anesthesia involves injecting anesthesia/analgesics into the epidural space (lumbar/thoracic).
    • Caudal anesthesia involves injection into the sacral hiatus.
    • Spinal anesthesia refers to injection into the intrathecal space (also known as: spinal block, subarachnoid block, intrathecal block).

    Neuraxial Analgesia vs. Anesthesia

    • Anesthesia: Intense sensory and motor blockade, usually obtained with high local anesthetic concentration (e.g., 2% lidocaine).
    • Analgesia: Sensory blockade only, often used for pain management or labor analgesia.

    ### Advantages of Neuraxial Anesthesia

    • Reduced metabolic stress response
    • Reduced blood loss (e.g., in cesarean sections and lower extremity surgeries)
    • Decreased venous thromboembolic complications
    • Reduced pulmonary compromise
    • Avoidance of airway manipulation
    • Mental status remains intact
    • Reduced total systemic drug dose
    • Motor blockade eliminates need for muscle relaxants and subsequent reversal medications
    • Lower incidence of postoperative nausea and vomiting

    Spinal vs. Epidural Anesthesia

    • Spinal Anesthesia:
      • Involves direct injection into the CSF.
      • Produces rapid and dense neural blockade.
      • Often quicker onset.
      • More predictable block density, particularly regarding motor blockade.
      • Less risk for block "patchiness" and/or unilateral block.
      • Lower volume of local anesthetic required.
    • Epidural Anesthesia:
      • Involves injecting local anesthetic into the epidural space, surrounding the dura mater.
      • Produces a slower onset and often less dense block.
      • Block is often segmental (a band of anesthesia).
      • Requires a larger needle and often a continuous catheter technique.
      • Placement involves locating the epidural space by feeling the ligaments.
      • The epidural space lies between the dura mater and the vertebral canal.

    Disadvantages of Single-Shot Spinal Anesthesia

    • More immediate and dramatic hemodynamic changes.
    • Not easily titratable.
    • Limited ability to provide continued analgesia beyond initial dose.
    • Cannot be augmented or modified once set.

    Assessing a Patient for Neuraxial Anesthesia

    • Prior back injury or surgery
    • Neurological symptoms or history of neurological disease
    • Bleeding tendencies or diseases associated with coagulopathy
    • Anticoagulation or antiplatelet medication
    • Prior regional anesthesia and any associated problems
    • Brief neurological examination for strength and sensation
    • Back examination for landmarks and potential abnormalities
    • Cardiovascular examination
    • Expected duration and blood loss of surgery
    • Positioning required
    • Need for muscle relaxation
    • Surgeon's preferences
    • Patient explanation of procedure, risks, benefits, and options
    • Patient sedation preference
    • Laboratory tests as needed
    • Imaging (magnetic resonance imaging and/or computed tomography)

    Epidural Space Anatomy

    • Lies just outside the dural sac, containing the spinal cord and CSF.
    • From superficial to deep: skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, spinal meninges and CSF.
    • Widest point is at L2.
    • Contains: fat, lymphatics, and an extensive venous plexus (Batson plexus).
    • Wraps around the dural membrane.
    • Extends superiorly to the foramen magnum.
    • Extends caudally to the sacral hiatus.

    Performing a Lumbar Epidural Anesthetic

    • Ensure resuscitation equipment is readily available.
    • Monitor patient with pulse oximeter and blood pressure cuff.
    • Establish a well-running IV line and consider a fluid coload to counteract hypotension.
    • Patient positioning: sitting or lying laterally, spinous processes aligned, maximally flexed.
    • Sedation as appropriate.
    • Visualize a line between the iliac crests to locate the L4 spinous process.
    • Palpate the L2-L3, L3-L4, and L4-L5 interspaces.
    • Maintain sterile technique and follow strict aseptic procedures with appropriate attire.
    • Skin wheal with local anesthetic at the desired insertion site.
    • Epidural needle is most often inserted in the midline.
    • Recognize resistance from various layers of ligaments.
    • Loss of resistance when the needle passes through ligamentum flavum and enters the epidural space.
    • Thread a catheter into the epidural space.
    • Aspirate for blood or CSF.
    • Administer a test dose if aspirate is negative.
    • Secure the catheter in place.

    Paramedian Epidural Placement

    • Identify the spinous process at the desired interspace level.
    • Create a skin wheal 1-2 fingerbreadths lateral to the spinous process.
    • Insert the needle through the wheal until encountering the transverse process of the vertebra.
    • "Walk" the needle off the transverse process superiorly and medially until engaging with the ligamentum flavum.
    • Advance until loss of resistance is achieved.
    • Useful at high thoracic levels where the spinous processes are acutely angled downward.

    Caudal Anesthesia

    • A form of epidural anesthesia where the injection is made at the sacral hiatus (S5).
    • Dural sac typically ends at S2, minimizing the risk of accidental spinal injection.
    • Provides dense sacral and lower lumbar levels of block.
    • Use in adults is limited by highly variable anatomy, calcification/ossification of ligaments, and risk of venous plexus injection.
    • Primarily used in children for postoperative analgesia.

    Combined Spinal-Epidural (CSE) Anesthetic

    • Performed by passing a long spinal needle through an epidural needle that has been placed into the epidural space.
    • Dura is punctured, confirming epidural needle placement adjacent to the dura.
    • A dose of local anesthetic with or without adjuvants is deposited in the subarachnoid space.
    • Results in a faster onset of block.
    • Combines the advantages of both spinal and epidural anesthesia.
    • Relatively reliable epidural catheter.

    Physiological Changes After Epidural Anesthesia

    • Decreased blood pressure.
    • Changes in heart rate: Tachycardia may occur to compensate for decreased vascular resistance, bradycardia may occur due to vagal stimulation or high block levels.
    • Ventilatory changes: In normal patients, ventilation is maintained as long as the diaphragm is not impaired, but patients may experience subjective dyspnea as they lose sensation in intercostal muscles.
    • Bladder distention due to sympathetic blockade.
    • Changes in thermoregulation.
    • Neuroendocrine changes: Blocks sympathetic afferents to the adrenal medulla, inhibiting the stress response.

    Common Local Anesthetics used in Epidural Anesthesia

    • Chloroprocaine
    • Lidocaine
    • Bupivacaine
    • Ropivacaine
    • Tetracaine

    Intrathecal Space Anatomy

    • From superficial to deep: skin, subcutaneous/adipose tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, dura mater, arachnoid membrane.

    Boney Structures Encountered During Intrathecal Injection

    • Shallow osseous tissue: Spinous process.
    • Deep osseous tissue: Vertebral lamina.

    Principal Sites of Effect of Spinal Local Anesthetics

    • Sodium channels in the spinal nerve roots and spinal cord itself.

    Factors Determining Spinal Anesthesia Termination

    • Dissociation of the local anesthetic from nerve sodium channels.
    • Resorption of the agent from the CSF into the systemic circulation.

    Factors Influencing Spinal Blockade Distribution

    • Patient characteristics: height, position, intraabdominal pressure, spinal canal configuration, pregnancy.
    • Total injected milligram dose of the local anesthetic.
    • Baricity of the local anesthetic solution.
    • Patient position during and after injection.

    Lumbar Levels for Spinal Anesthesia

    • Below L1 in adults, and L3 in children to avoid spinal cord trauma.
    • L3-L4 interspace is often thought to be located at the line intersecting the top of the iliac crests.

    Complications of Neuraxial Anesthesia

    • Hypotension (can be significant)

    • Bradycardia

    • Respiratory depression

    • Postdural puncture headache

    • Nausea and vomiting

    • Urinary retention

    • Back pain

    • Infection

    • Bleeding### Neuraxial Anesthesia Complications

    • Hypotension is common, caused by sympatholysis leading to decreased arterial pressure and increased venous capacitance.

    • Factors increasing hypotension risk: hypovolemia, age over 40, sensory level above T5, baseline systolic blood pressure below 120 mmHg, block at or above L3-L4.

    • Treatment: Vasopressor infusion (e.g., phenylephrine), fluid resuscitation for hypovolemia.

    • Pruritus: Often from intrathecal narcotics.

    • Nausea and vomiting: Often secondary to hypotension.

    • Postdural puncture headache (PDPH): A common complication.

    • Rare but serious complications: nerve injury, cauda equina syndrome, meningitis, high/total spinal anesthesia, spinal hematoma/abscess formation.

    • Local anesthetic toxicity (LAST): May occur with intravascular injection of large local anesthetic doses. Prevented by negative aspiration, epinephrine as an additive, and incremental dosing.

    • Bradycardia: May occur due to unopposed vagal tone, blockade of cardioaccelerator fibers, Bezold-Jarisch or reverse Bainbridge reflexes.

    Neuraxial Anesthesia and Anticoagulation

    • Heparin: For doses over 20,000 units daily, wait 24 hours and recheck coagulation status (PTT).
    • IV Heparin: 4-6 hours with proven PTT normalization is usually adequate for clearance.
    • LMWH: Needle placement should occur at least 12 hours after prophylactic dose (e.g., 40 mg enoxaparin daily), and 24 hours for other regimens.

    Neuraxial Opioids

    • Effects: Intense visceral analgesia, prolonged sensory blockade, without affecting motor or sympathetic function.
    • Mechanism: Act on opiate receptors in the spinal cord.
    • Lipophilic agents (fentanyl, sufentanil): Localized effect, rapid onset, long duration.
    • Hydrophilic agents (morphine): Gradual onset, longer duration.
    • Side effects: Respiratory depression, nausea, vomiting, pruritus, urinary retention.

    Transient Neurological Syndrome (TNS)

    • Symptoms: Pain or dysesthesia in buttocks radiating to thighs and calves, often worse at night.
    • Usually resolves: Within a week.
    • Associated with: Lidocaine spinal anesthesia.
    • Risk factors: Lithotomy position, ambulatory surgery patients.
    • No objective neurological findings: On physical examination.

    Choosing Local Anesthetics

    • Factors considered: Onset, duration, safety profile, patient characteristics, and procedure.
    • Epinephrine: Often added for vasoconstriction, improved analgesia, and detection of intravascular injection.

    Epidural Anesthesia

    • Motor block: Degree can be decreased by lowering anesthetic concentration and choosing agents with sensory-motor dissociation.
    • Sensory block: Can be augmented with epidural opiods.
    • Bupivacaine and ropivacaine: Offer less motor block for a given sensory block.

    Surgical Blockade

    • Level of anesthesia: Determined by the innervation of structures involved in the procedure.
    • Testing: Sensory level tested before incision.

    Segmental Block

    • Epidural anesthesia: Segmental, most intense near catheter insertion, diminishing with distance.
    • Placement: Close to surgical site.

    Continuous Spinal Anesthesia

    • Technique: Regaining popularity. Safe and effective with proper techniques.
    • Advantages: Less hypotension, titration of anesthetic.

    Enhanced Recovery After Surgery (ERAS)

    • Protocols: Combine evidenced-based perioperative care to improve outcomes.
    • Neuraxial anesthesia: Key component, minimizes systemic opioid use.

    Postoperative Assessment

    • Satisfaction: Assess and address any concerns or misunderstandings.
    • Block regression: Evaluate sensory and motor function, bowel and bladder function.
    • Back pain: Check for bruising, redness, or swelling.
    • Headache: Observe for PDPH, especially if dural puncture occurred.
    • Pain relief: Assess adequacy.
    • Side effects: Monitor for and manage any adverse effects.

    Peripheral Nerve Blocks

    • Indications: Anesthesia or analgesia.
    • Benefits: Avoid general anesthesia, decrease opioid use.

    Contraindications to Peripheral Nerve Blocks

    • Anticoagulation: Increased risk of hematoma and nerve damage.
    • Peripheral neuropathy: Potential for increased risk of nerve injury.
    • Compartment syndrome: Can mask diagnosis.
    • Systemic infection: Risk of perineural abscess.

    Upper Extremity Nerve Blocks

    • Brachial plexus blocks: Most common for upper extremity procedures.
    • Types: Interscalene, supraclavicular, infraclavicular, axillary.
    • Individualized nerve blocks: Radial, median, and ulnar nerve blocks for hand and finger analgesia.

    Choosing Brachial Plexus Blocks

    • Interscalene block: Suitable for shoulder, clavicle, and proximal humerus procedures.
    • Supraclavicular, infraclavicular, and axillary blocks: Depending on surgical site and patient positioning.

    Brachial Plexus Nerve Blocks For Upper Extremity Surgery

    • Supraclavicular Brachial Plexus Block
      • Provides anesthesia from below the deltoid to the fingers
      • Can be effective for shoulder surgery depending on technique
      • Approximately 50% chance of phrenic nerve blockade
      • Increased risk of pneumothorax
      • Ultrasound guidance advised
    • Infraclavicular Brachial Plexus Block
      • Provides anesthesia from the mid-humerus to the fingers
      • Can be more technically challenging because of the steep approach required
    • Axillary Brachial Plexus Block
      • Provides anesthesia from the mid-humerus to the fingers
      • Frequently spares musculocutaneous nerve - requires separate block
      • Requires patient to abduct arm

    Brachial Plexus Nerve Block Techniques

    • Supraclavicular Nerve Block
      • Performed in the semi-sitting position with the head turned to the opposite side
      • Patient’s arm is reached to the ipsilateral lower extremity, shoulder is externally rotated to depress the clavicle and increase space for ultrasound probe
      • Needle advanced from lateral to medial to surround the divisions of brachial plexus lateral to the subclavain artery
      • Care must be taken to avoid traversing arteries, as anatomy varies in the supraclavicular region
    • Infraclavicular Nerve Block
      • Deep block with benefits of avoiding phrenic nerve paralysis and accommodate peripheral nerve catheters
      • Patient positioned supine, arm is positioned at the patient’s side or above the head to elevate the clavicle and increase room for the ultrasound probe
      • Probe oriented cephalad to caudad at the level of the coracoid process
      • Needle advanced until it reaches the 6 o’clock position of the axillary artery, local anesthetic is deposited
      • Block provides coverage of all three cords of the brachial plexus with one injection
    • Axillary Nerve Block
      • Patient’s arm abducted to approximately 90 degrees
      • Transducer placed along the medial aspect of the arm in the axilla. Needle transversed from cephalad to caudad to the 6 o’clock position of the axillary artery
      • Multiple injections often required to achieve circumferential spread to anesthetize the median, ulnar, and radial nerves
      • Separate needle insertion point required to anesthetize the musculocutaneous nerve for distal forearm coverage

    Risks of Brachial Plexus Nerve Blocks

    • Supraclavicular Brachial Plexus Block
      • Increased risk of pneumothorax compared with infraclavicular and axillary approaches because of the block site's close proximity to the pleura
      • Risk remains very low with ultrasound guidance
      • Care must be taken to avoid intravascular injection in the subclavian artery, dorsal scapular and suprascapular arteries
    • Infraclavicular Brachial Plexus Block
      • Increased risk of intravascular injection
      • Target site depth and steep angle of insertion make needle visualization difficult
      • Aspiration before every injection is important to ensure the tip is not in the axillary artery or adjacent vein
      • More difficult to visualize small arteries and veins at lower depths
    • Axillary Brachial Plexus Block
      • Lowest amount of risk compared to other brachial plexus blocks
      • Axillary artery is superficially located and compressible, making manual compression viable for preventing hematoma formation

    Managing Complications With Brachial Plexus Nerve Blocks

    • Perform neurologic examination to evaluate motor and sensory function of the median, radial, and ulnar nerves if a supraclavicular nerve block results in a motor block of the arm but the patient can still feel pain in one finger.
    • Most likely, there has been ulnar nerve sparing from inadequate block of the lower trunk.
    • This may occur due to a deficiency of local anesthetic in the "corner pocket," where the lower trunk is located
    • A supplementary rescue block can be performed to anesthetize this area, but there is a theoretical increased risk of nerve damage with the passage of a needle through already anesthetized nerves.
    • Another option would be to block the ulnar nerve more distally.

    Lower Extremity Nerve Blocks

    • Nerves of the lower extremity are derived from the lumbar plexus (L1–L5) and the sacral plexus (L4–S3)
    • Lumbar plexus gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Most common lumbar plexus blocks are the lumbar plexus, femoral, and saphenous nerve blocks
    • Sacral plexus gives rise to the sciatic nerve, as well as the superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh.
    • Most common sacral plexus blocks are the transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks
    • To achieve surgical anesthesia of the lower extremity, a combination of sciatic and femoral blocks will need to be performed.

    Choosing the Appropriate Lower Extremity Nerve Block for Procedures

    • Location of the surgery, possible application of a tourniquet, and need for postoperative motor function should all be considered with each block.
    • For example, to provide complete anesthesia of the ankle for operative fixation, both a popliteal sciatic and saphenous nerve block would need to be used.
    • However, this choice would not offer analgesia for pain from a thigh tourniquet, therefore a more proximal choice, such as a subgluteal sciatic and lumbar plexus block would be necessary.
    • An ankle block is effective for surgery on the toes and forefoot, but the hindfoot is usually spared.

    Techniques for Lower Extremity Nerve Blocks

    • Lumbar Plexus Block
      • Deep block
      • Needle insertion point is 4 to 5 cm lateral to the L4-L5 interspace
      • Block is primarily performed with nerve stimulator guidance, until contraction of the quadriceps muscle is elicited
      • Located in the body of the psoas major muscle, typically 2 cm deep to the transverse process of the lumbar spine.
      • Depth of needle insertion is often between 6 and 8 cm, depending on body habitus
    • Femoral Nerve Block
      • Popular block for anesthesia of the anterolateral thigh and the medial skin below the knee
      • Can be visualized under ultrasound guidance 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle.
    • Saphenous Nerve Block
      • Located more distal in the lower extremity, often blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • Sciatic Nerve Block
      • Found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur
      • Subgluteal approach is often less technically challenging and easier to visualize by ultrasound
    • Popliteal Sciatic Nerve Block
      • Sciatic nerve has a variable branch point into the common peroneal and tibial nerves in the popliteal region.
      • Under ultrasound guidance, the sciatic nerve can be found posterior to the femur and posterolateral to the popliteal artery
      • Muscle borders of the nerve include the semitendinosus and semimembranosus medially and the biceps femoris laterally

    Risks of Lower Extremity Nerve Blocks

    • Nerve injury, intravascular injection, infection, and damage to surrounding structures
    • Nerve injury is rare and not completely understood
    • Preexisting neuropathy is more common in the lower extremities, increasing the risk for nerve damage from intraneural injection, ischemia, or toxicity from local anesthetics
    • Blocks such as lumbar plexus blocks pose increased and unique risks because of the depth of the block and its proximity to several vulnerable structures
    • Aortic perforation with retroperitoneal hematoma, intrathecal injection, and even bowel perforation, have been reported with lumbar plexus blocks.

    Plane Blocks vs. Peripheral Nerve Blocks

    • Plane block involves anatomy where no distinct nerve needs to be identified
    • Involves infiltrating local anesthetic into fascial planes where various nerves are known to traverse
    • Technique has given rise to numerous new blocks that offer analgesia to the abdomen, chest, and trunk
    • Typically require a higher volume of local anesthetic to be effective compared with standard peripheral nerve blocks.
    • Risk of direct nerve damage from the needle is reduced because the individual nerves are either small or not present at the location of injection

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    • Thoracic Paravertebral Block
      • Local anesthetic deposited in the paravertebral space where the thoracic spinal nerves and sympathetic trunk reside.
      • Results in three to seven dermatomes of unilateral anesthesia to the abdomen or chest wall surrounding the insertion point.
      • Good choice for smaller thoracic, abdominal, or breast surgeries.
    • Transversus Abdominis Plane (TAP) Block
      • Indicated for lower abdominal surgeries, such as hysterectomy or hernia repair
      • Local anesthetic deposited in the fascial plane, between the internal oblique and transversus abdominis muscles
      • Anterior divisions of T10–L1 and ilihypogastric and ilioinguinal nerves lie in this plane, with some variations in anatomy
      • Results in unilateral anesthesia of the lower anterior abdominal wall, including the groin.
      • Upper abdomen can also be blocked using the subcostal TAP approach
      • Bilateral blocks can be used for midline surgeries, observing limits of local anesthetic dosing to avoid toxicity.

    Truncal Nerve Blocks

    • Erector Spinae Block

      • Injection plane: Between transverse process of vertebra and the erector spinae muscles
      • Nerves blocked: Thoracic/lumbar spinal nerves
      • Surgical Indications: Breast, chest, upper and lower abdominal surgery depending on injection point

    • PECS Block (two types)

      • Type I: Injection plane: Between pectoralis major and pectoralis minor
        • Nerves blocked: Lateral and medial pectoral nerves
        • Surgical Indications: Partial coverage for breast surgery
      • Type II: Injection plane: Between pectoralis minor and serratus anterior
        • Nerves blocked: Thoracic intercostal nerves and long thoracic nerve
        • Surgical Indications: Breast surgery including axillary dissection

    • Serratus Anterior Block

      • Injection plane: Deep to the serratus anterior muscle
      • Nerves blocked: Thoracic intercostal nerves, thoracodorsal, and long thoracic nerves
      • Surgical Indications: Procedures of the hemi-thorax, including breast and thoracic surgery

    • Quadratus Lumborum Block

      • Injection plane: Anterolateral border of the quadratus lumborum muscle
      • Nerves blocked: Thoracic/lumbar spinal nerves
      • Surgical Indications: Upper or lower abdominal surgeries

    Risks of Truncal Nerve Blocks

    • Paravertebral Blocks
      • Pleural puncture and injection resulting in pneumothorax due to proximity to the pleura
      • Epidural spread is possible, resulting in unintended contralateral effects and possible hemodynamic changes
      • Vagal reaction common
    • TAP Blocks
      • Rare serious complications
      • Intraperitoneal injection possible
      • Injury to abdominal viscera possible

    Advantages and Disadvantages of Truncal Nerve Blocks

    • Paravertebral Block
      • Advantages: Versatile, provides dense analgesia that can be effective for surgical anesthesia
      • Disadvantages: Higher risk than other truncal blocks because of its location
    • Pecs Block
    • Advantages: Easier to perform than paravertebral block, provides equivalent analgesia with lower potential risk, blocks pectoral nerves which are spared by other techniques
    • Disadvantages: None described in the text
    • Serratus Anterior Block
      • Advantages: Easier to perform than paravertebral block, provides equivalent analgesia with lower potential risk
      • Disadvantages: None described in the text
    • TAP Block
      • Advantages: Easier to perform than the paravertebral block and is lower risk
      • Disadvantages: None described in the text
    • Quadratus Lumborum Block
      • Advantages: Covers more dermatomes per injection relative to the TAP block
      • Disadvantages: Cannot be performed in the supine position, more challenging than the TAP block
    • Erector Spinae Block
      • Advantages: Lower risk for direct injury or nerve threatening hematoma because it is farther from sensitive structures, such as the spinal cord.
      • Disadvantages: Benefits not well described in the literature, likely delivers less effective analgesia than the paravertebral block

    Key Points: Peripheral Nerve and Trunk Blocks

    • Nerve blocks are generally performed for 2 major indications: anesthesia or analgesia.
    • May allow patients to avoid general anesthesia and periprocedural pain medication.
    • Most upper extremity nerve blocks involve blocking the brachial plexus.
    • Most lower extremity nerve blocks involve blocking the lumbar plexus or sacral plexus.
    • Increased use of ultrasound has resulted in many novel truncal blocks that are on the forefront of regional anesthesia.

    Indications and Contraindications for Regional Anesthesia

    • Peripheral nerve blocks can be used for surgical anesthesia and pain management for various surgeries.
    • Common surgeries performed with nerve blocks include orthopedic procedures, amputations, thoracotomies, laparotomies, and mastectomies.
    • Contraindications for peripheral nerve block include patient refusal, infections, pre-existing neuropathy, and coagulopathy.

    Advantages and Disadvantages of Peripheral Nerve Blockade vs. General Anesthesia

    • Regional anesthesia can be helpful for patients with anticipated difficult airways, severe cardiopulmonary disease, obstructive sleep apnea, severe postoperative nausea and vomiting, chronic opioid therapy, opioid abuse history, allergies to analgesics.
    • Procedures performed under regional anesthesia require patient cooperation, making it unsuitable for children, patients with high anxiety, developmental delay, altered mental status, or dementia.
    • Preoperative nerve blocks may be inflexible if surgical plans change.
    • Regional blocks are often performed alongside general anesthesia to address these limitations.

    Methods for Providing Regional Anesthesia

    • Peripheral nerve blocks can be performed as a single injection or a continuous infusion via an indwelling catheter.
    • Neuraxial blockade can be administered as an injection into the subarachnoid space (spinal anesthesia) or a continuous infusion into the epidural space.
    • IV regional anesthesia (Bier block) involves injecting local anesthetic intravenously into an extremity with an inflated tourniquet.

    Bier Block Technique

    • An IV is placed in the operative extremity.
    • The extremity is elevated and exsanguinated.
    • A double tourniquet is inflated, and lidocaine is injected intravenously.
    • The extremity is lowered, the IV is removed, and the surgical procedure can proceed.
    • This block is typically used for procedures lasting 30 to 45 minutes due to tourniquet pain limitations.

    Peripheral Nerve Block Techniques

    • Most peripheral nerve blocks today are performed using ultrasound guidance, allowing direct visualization of local anesthetic spread.
    • Nerve stimulation is an older technique that can be used alone or with ultrasound, especially in cases of difficult anatomical identification.
    • Some blocks can be performed using anatomical landmarks or subcutaneous infiltration (field block).

    Ultrasound-Guided Nerve Block Technique

    • Ultrasound images guide needle advancement and local anesthetic injection around neural structures.
    • In-plane (IP) approach involves advancing the needle in the plane of the ultrasound beam, allowing visualization of the entire needle shaft.
    • Out-of-plane (OP) approach advances the needle perpendicular to the ultrasound beam, visualizing only a cross-section of the needle.
    • The IP approach is preferred as it provides a comprehensive view of the needle’s trajectory, facilitating the avoidance of important structures.
    • The OP approach is useful for its shorter and more direct path to the nerve.
    • Ultrasound allows for better visualization of anatomical structures, decreasing complications, visualizing blood vessels to minimize bleeding, and identifying anatomical variations that could limit block effectiveness.
    • The primary disadvantage of ultrasound guidance is the requirement for specialized and expensive equipment.

    Nerve Stimulator Technique

    • A nerve stimulator device emits an electrical stimulus through an insulated block needle.
    • The needle is advanced until muscle twitching or paresthesias, specific to the targeted nerve, are elicited.
    • Decreasing the stimulus intensity until the response disappears confirms close proximity to the nerve.
    • A response at 0.3 mA indicates intraneural placement, requiring needle withdrawal before injection.
    • The nerve stimulator technique is most often used with ultrasound, especially when ultrasound visualization is difficult.

    Sonographic Resolution

    • Axial resolution refers to the clarity of structures along the axis of the ultrasound beam and is dependent on pulse wavelength and cycles per pulse.
    • Lateral resolution describes the clarity between two adjacent structures located the same distance from the probe, improving with increased wave frequency and decreased ultrasound beam width.
    • Temporal resolution relates to dynamic structures and improves with increased ultrasound frame rate.

    Optimizing Visualization Under Ultrasound

    • Select an ultrasound probe with appropriate frequency based on the target structure's depth.
    • Confirm probe orientation and apply sufficient gel.
    • Adjust gain and time-gain compensation to improve image quality.
    • Utilize Doppler ultrasound to identify pulsating blood vessels or local anesthetic spread.
    • Ensure the needle is aligned with the ultrasound beam for clear visualization in IP needle approaches.
    • Adjust probe tilt and puncture the skin farther away from the probe to visualize the entire needle shaft for deeper structures.
    • Echogenic needles enhance visualization.

    Anatomy of the Paravertebral Space

    • The superior costotransverse ligament forms the posterior border of the paravertebral space.
    • The anterolateral border is formed by the parietal pleura, and the vertebral bodies and intervertebral disks form the medial border.
    • The paravertebral space houses the thoracic spinal nerves and the sympathetic trunk.

    Muscles of the Anterolateral Abdomen

    • From superficial to deep, the muscles of the anterolateral abdomen consist of the external oblique, internal oblique, and transverse abdominis.
    • These muscles are innervated by the anterior rami of T7–L1.
    • Blocks targeting this area include the transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks.

    Brachial Plexus

    • The brachial plexus is formed from the C5–T1 nerve roots.
    • Its subdivisions include roots, trunks, divisions, cords, and branches.
    • Blocks targeting this area include interscalene, supraclavicular, infraclavicular brachial plexus nerve blocks, axillary, and various forearm nerve blocks.

    Lumbar Plexus

    • The lumbar plexus is formed from the T12–L4 nerve roots.
    • It branches into the ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Blocks targeting this area include lumbar plexus, femoral, and fascia iliaca blocks.

    Sciatic Nerve

    • The sciatic nerve innervates the majority of the lower extremity, excluding the anterior thigh and the medial calf, which are innervated by the lumbar plexus.
    • It arises from the L4–S3 nerve roots and branches into the tibial and common peroneal nerves.
    • Blocks targeting this nerve can be performed proximally (anterior, transgluteal, subgluteal) or at the popliteal fossa. Its branches can also be blocked at the ankle.

    Cutaneous Innervation of the Ankle

    • The ankle is innervated by five nerves: tibial, saphenous, deep peroneal, superficial peroneal, and sural.
    • The tibial nerve innervates most of the heel and plantar surface of the foot.
    • The saphenous nerve innervates the medial aspect of the lower leg and ankle.
    • The superficial peroneal nerve innervates most of the dorsum of the foot.
    • The deep peroneal nerve innervates a small area at the webspace between the great and second toes.
    • The sural nerve innervates the lateral ankle.

    Complications of Regional Anesthesia

    • Complications include bleeding, infection, intravascular or intraneural injection (leading to LAST or nerve damage), allergic reactions, damage to adjacent structures, and block failure.
    • Interscalene and supraclavicular blocks are associated with phrenic nerve involvement (ipsilateral diaphragmatic paresis), sympathetic chain involvement (ipsilateral Horner syndrome), and recurrent laryngeal nerve involvement (hoarseness).
    • Subarachnoid or epidural injection and pneumothorax are other possible complications.

    Decreasing the Risk of Complications

    • Use sterile technique, ensure the patient is on appropriate monitors, and inject local anesthetic in small increments, aspirating before each injection.
    • Allow for one complete circulation time after injecting 10 cc to assess for systemic toxicity.
    • Stop injecting and withdraw the needle slightly if the patient experiences sharp pain or paresthesias.
    • Do not advance the needle without visualizing the tip in ultrasound-guided blocks.
    • Do not inject local anesthetic if a twitch response is obtained below 0.3 mA in nerve stimulator blocks.
    • Continuously monitor patients for changes in hemodynamics and mental status.

    Local Anesthetics

    • Local anesthetics are categorized by duration of action: short, intermediate, and long.
    • 2-Chloroprocaine is a short-acting local anesthetic, metabolized rapidly by plasma cholinesterases, allowing for high concentrations with minimal toxicity.
    • Lidocaine and mepivacaine are commonly used intermediate-acting local anesthetics, often preferred over longer-lasting drugs.
    • Ropivacaine and bupivacaine are commonly used for blocks requiring longer duration, with a slower onset of action and prolonged analgesia.
    • Bupivacaine has higher cardiotoxicity and causes more motor blockade than ropivacaine.

    Additives to Local Anesthetics

    • Vasoconstrictors, such as epinephrine, are commonly added to local anesthetics to prolong block duration and decrease systemic absorption.
    • Sodium bicarbonate alkalinizes the pH of the local anesthetic solution, decreasing the time to block onset.
    • Clonidine, an alpha-2 agonist, may improve block quality and prolong duration when combined with local anesthetics.
    • Other medications thought to prolong block duration include dexamethasone and dexmedetomidine.

    Factors Affecting Local Anesthetic Onset of Action and Potency

    • A local anesthetic’s onset of action depends on its pKa, with a pKa closer to the body’s pH leading to a quicker onset.
    • Local anesthetic potency correlates with lipid solubility, with more lipid-soluble drugs requiring lower concentrations to achieve the same effect.
    • Factors influencing block duration include the type of local anesthetic, presence/absence of a vasoconstrictor, lipid solubility, and protein binding.

    Local Anesthetic Systemic Toxicity (LAST)

    • LAST can result from perineural injection of large doses of local anesthetic, as well as from accidental intravascular, intrathecal, or epidural injection.
    • CNS signs classically precede cardiovascular signs, consisting of an excitatory phase followed by a depressive phase.
    • The excitatory phase is characterized by tinnitus, circumoral numbness, lightheadedness, altered mental status, tremors, and tonic-clonic seizures.
    • The depressive phase may feature respiratory depression, coma, and respiratory arrest.
    • Cardiovascular effects include hypotension, conduction disturbances, ventricular arrhythmias, and myocardial depression.
    • Lidocaine, while generally considered less likely to cause systemic toxicity than bupivacaine or ropivacaine, has been implicated in LAST in various case reports.

    Treatment of LAST

    • Treatment of LAST involves managing CNS and cardiovascular symptoms with appropriate measures, including airway management, ventilation, cardiovascular support, and administration of anticonvulsants.
    • Cardiac arrest in the setting of LAST requires specific management strategies due to unique characteristics of the condition.

    Summary

    This study guide provides a comprehensive overview of regional anesthesia, covering indications, contraindications, advantages, disadvantages, various techniques, complications, risk mitigation strategies, local anesthetic characteristics, additives, and management of LAST. It is important for students to understand these concepts to ensure safe and effective use of regional anesthesia.### LAST Treatment Algorithm

    • Discontinue all local anesthetic administration immediately.
    • Call for help and retrieve a LAST rescue kit.
    • Alert the cardiopulmonary bypass team.
    • Provide 100% oxygen ventilation, insert an advanced airway if needed.
    • Treat seizures with benzodiazepines.
    • Consider lipid emulsion therapy promptly at the first sign of a severe LAST event.
    • Propofol is not an adequate alternative and may cause hypotension.
    • Treat hypotension and bradycardia.
    • Start CPR if the patient becomes pulseless.
    • Continuous monitoring for 4-6 hours after a cardiovascular event or at least 2 hours after a CNS event.
    • Reduce epinephrine boluses to 1 mcg/kg or less.
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers.

    Lipid Emulsion Dosing for LAST

    • Patients > 70 kg: bolus with 100 mL 20% lipid emulsion over 2-3 minutes, followed by 200-250 mL infusion over 15-20 minutes.
    • Patients < 70 kg: bolus with 1.5 mL/kg, followed by 0.25 mL/kg/min ideal body weight infusion
    • If the patient remains unstable after treatment, rebolus at the same dose 1-2 times and double the infusion rate.
    • Do not exceed 12 mL/kg maximum dose.

    Benefits of Regional Anesthesia

    • Avoids general anesthesia when appropriate
    • Provides pain control, especially for patients with difficult airways or intolerance to general anesthesia
    • Analgesic blocks can minimize opioid use, improving postoperative pain scores, increasing patient satisfaction, decreasing nausea, and decreasing the likelihood of admission for pain management.

    Considerations for Peripheral Nerve Blocks

    • Contraindications:
      • Anticoagulation
      • Peripheral Neuropathy
      • Traumatic Injury (risk of masking compartment syndrome)
      • Systemic Infection (risk of perineural abscess)

    Common Upper Extremity Nerve Blocks

    • Brachial Plexus Block: Interscalene, supraclavicular, infraclavicular, axillary
    • Supraclavicular Block is considered mainstay for procedures below the shoulder.
    • Individualized Radial, Median, and Ulnar Nerve Blocks can be performed under ultrasound guidance to offer analgesia to the hand and fingers.

    Choosing Brachial Plexus Blocks

    • Interscalene: Procedures on shoulder, distal clavicle, proximal humerus
    • Supraclavicular, Infraclavicular, and Axillary: Covered in Table 69.1
      • Supraclavicular: Anesthesia below deltoid to fingers. Effective for shoulder surgery depending on technique. 50% chance of phrenic nerve blockade
      • Infraclavicular: Anesthesia from mid-humerus to fingers.
      • Axillary: Anesthesia from mid-humerus to fingers. Usually spares musculocutaneous nerve, requiring separate block.

    Anatomical Landmarks and Technique

    Supraclavicular Nerve Block

    • Patient Position: Semi-sitting, head turned opposite the block site. Arm to ipsilateral lower extremity, shoulder externally rotated to depress clavicle.
    • Needle Insertion: Lateral to medial, surrounding brachial plexus divisions, lateral to the subclavian artery.
    • Caution: Avoid traversing arteries, anatomy varies.

    Infraclavicular Nerve Block

    • Patient Position: Supine, arm at side or above head.
    • Probe Placement: Cephalad to caudad at the level of the coracoid process.
    • Needle Insertion: To the 6 o’clock position of the axillary artery.
    • Goal: U shaped spread on both sides of the artery to avoid sparing the medial or lateral cords.

    Axillary Nerve Block

    • Patient Position: Arm abducted to 90 degrees.
    • Probe Placement: Medial aspect of arm in the axilla.
    • Needle Insertion: Cephalad to caudad to the 6 o’clock position of the axillary artery.
    • Multiple Injections: Usually required to anesthetize median, ulnar, and radial nerves.
    • Musculocutaneous Nerve Block: Often required separately to ensure distal forearm coverage.

    Risks of Brachial Plexus Blocks

    Supraclavicular

    • Increased Pneumothorax Risk: Use ultrasound guidance to minimize.
    • Intravascular Injection: Subclavian artery, dorsal scapular artery, suprascapular artery.

    Infraclavicular

    • Increased Intravascular Injection Risk: Deeper block, steep approach, use aspiration before every injection to avoid axillary artery or adjacent vein.
    • Difficulty Visualizing Small Vessels: At lower depths.

    Axillary

    • Lower Risk: Axillary artery is superficial and compressible, making manual compression effective in preventing hematomas.

    Managing Ulnar Nerve Sparing in Supraclavicular Block

    • Cause: Inadequate block of the lower trunk.
    • Evaluation: Neurological examination to evaluate median, radial, and ulnar nerve motor and sensory function.
    • Intervention:
      • Supplementary Rescue Block: Anesthetize the “corner pocket” between the first rib and subclavian artery (increased risk of nerve damage).
      • More Distal Ulnar Nerve Block: Another option.

    Common Lower Extremity Nerve Blocks

    • Lumbosacral Plexus: (L1-L5 and L4-S3)
      • Lumbar Plexus: Iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
        • Common blocks: Lumbar plexus, femoral, and saphenous.
      • Sacral Plexus: Sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and posterior cutaneous nerve of the thigh.
        • Common blocks: Transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.

    Choosing Lower Extremity Nerve Blocks

    • Considerations: Surgery location, tourniquet use, need for postoperative motor function.
    • Complete Anesthesia: Combination of sciatic and femoral blocks.
    • Example: Ankle surgery requires popliteal sciatic and saphenous nerve blocks.
    • Thigh Tourniquet Pain: Proximal blocks (subgluteal sciatic and lumbar plexus) for analgesia.
    • Ankle Block: Effective for toes and forefoot surgery, hindfoot usually spared.

    Anatomical Landmarks and Technique

    Lumbar Plexus Block

    • Patient Position: Supine
    • Needle Insertion Point: 4-5 cm lateral to L4-L5 interspace.
    • Technique: Nerve stimulator guidance until quadriceps muscle contraction.
    • Location: Psoas major muscle, 2 cm deep to the transverse process.
    • Depth: 6-8 cm depending on body habitus.

    Femoral Nerve Block

    • Patient Position: Supine
    • Technique: Ultrasound guidance
    • Location: 1 cm lateral to femoral artery, deep to fascia iliaca, superficial to iliopsoas muscle.
    • Saphenous Nerve: Distal in the lower extremity, blocked deep to sartorius muscle, inside the adductor canal, next to the superficial femoral artery.

    Sciatic Nerve Block (Proximal)

    • Patient Position: Supine
    • Location: Deep to the gluteus maximus, between ischial tuberosity and greater trochanter of the femur.
    • Subgluteal Approach: Easier to visualize by ultrasound.

    Sciatic Nerve Block (Popliteal)

    • Patient Position: Supine
    • Location: Posterior to the femur, posterolateral to the popliteal artery.
    • Muscle Borders: Semitendinosus and semimembranosus medially, biceps femoris laterally.

    Risks of Lower Extremity Nerve Blocks

    • Nerve Injury
    • Intravascular Injection
    • Infection
    • Damage to surrounding structures
    • Preexisting Neuropathy: Increases risk of nerve damage.
    • Lumbar Plexus Block Specific Risks:
      • Increased risks due to depth and proximity to vulnerable structures
      • Reported Cases: Aortic perforation, retroperitoneal hematoma, intrathecal injection, bowel perforation.

    Plane Blocks vs. Peripheral Nerve Blocks

    • Plane Blocks: Infiltrate local anesthetic in fascial planes, where nerves traverse.
    • Benefits:
      • No need to identify specific nerves
      • Reduced risk of direct nerve damage from the needle.
      • Increased use of ultrasound has expanded this technique.
    • Examples: Analgesia for abdomen, chest, and trunk.
    • Higher Volume of Local Anesthetic: Required compared to peripheral nerve blocks.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    Thoracic Paravertebral Block

    • Location: Paravertebral space where thoracic spinal nerves and sympathetic trunk reside.
    • Effect: Unilateral anesthesia of 3-7 dermatomes.
    • Indications: Small thoracic, abdominal, or breast surgeries.

    Transversus Abdominis Plane (TAP) Block

    • Location: Fascial plane between internal oblique and transversus abdominis muscles.
    • Nerves: Anterior divisions of T10-L1, ilihypogastric and ilioinguinal.
    • Effect: Unilateral anesthesia of lower anterior abdominal wall.
    • Indications: Lower abdominal surgeries (hysterectomy, hernia repair).
    • Subcostal TAP Approach: Blocks the upper abdomen
    • Bilateral Blocks: Can be used for midline surgeries.

    Other Truncal Nerve Blocks (Table 69.2)

    Fascial Plane Block Plane of Injection Nerves Blocked Surgical Indications
    Erector Spinae Between transverse process of vertebra and erector spinae muscles Thoracic/lumbar spinal nerves Breast, chest, upper and lower abdominal surgery
    PECS I Between pectoralis major and pectoralis minor Lateral and medial pectoral nerves. Partial breast surgery coverage Breast surgery
    PECS II Between pectoralis minor and serratus anterior Thoracic intercostal nerves and long thoracic nerve Breast surgery including axillary dissection
    Serratus Anterior Deep to serratus anterior muscle Thoracic intercostal nerves, thoracodorsal, and long thoracic nerves Procedures of the hemi-thorax (breast, thoracic surgery)
    Quadratus Lumborum Anterolateral border of the quadratus lumborum muscle Thoracic/lumbar spinal nerves Upper or lower abdominal surgeries

    Specific Risks of Truncal Nerve Blocks

    Paravertebral

    • Pleural Puncture: Pneumothorax
    • Epidural Spread: Unintended contralateral effects, hemodynamic changes
    • Vagal Reaction: Common

    TAP

    • Intraperitoneal Injection: Rare, potential abdominal viscera injury.

    Truncal Nerve Block Advantages and Disadvantages

    Paravertebral

    • Advantages: Versatile, dense analgesia, effective surgical anesthesia.
    • Disadvantages: Higher risk due to location.

    PECS & Serratus Anterior

    • Advantages: For breast surgery, easier performance, equivalent analgesia with lower risk. PECS blocks also block pectoral nerves.
    • Disadvantages: None listed.

    TAP & Quadratus Lumborum

    • Advantages: Easier performance than paravertebral, lower risk, extensive dermatome coverage (Quadratus Lumborum)
    • Disadvantages: Quadratus Lumborum not possible in supine position, more challenging than TAP.

    Erector Spinae

    • Advantages: Can be used for all paravertebral block indications, lower risk due to location.
    • Disadvantages: Benefits not well described in literature, likely less effective analgesia than paravertebral.

    Key Points: Peripheral Nerve and Trunk Blocks

    • Nerve blocks are primarily used for anesthesia or analgesia.
    • They may enable patients to avoid general anesthesia and periprocedural pain medication.

    Upper Extremity Nerve Blocks

    • Involve blocking the brachial plexus at different anatomic locations
    • Named based on their anatomic correlation for probe position or needle insertion

    Lower Extremity Nerve Blocks

    • Nerves of lower extremity originate from lumbar plexus (L1–L5) and sacral plexus (L4–S3)
    • Lumbar plexus: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves
    • Most common blocks from lumbar plexus: lumbar plexus, femoral, and saphenous nerve blocks
    • Sacral plexus: sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and posterior cutaneous nerve of the thigh
    • Most common blocks from sacral plexus: transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks
    • Increased use of ultrasound has led to novel truncal blocks

    Neuraxial Anesthesia

    • Epidural anesthesia: injection of anesthetics into epidural space at lumbar or thoracic level
    • Caudal anesthesia: injection into the sacral hiatus
    • Spinal anesthesia, spinal block, subarachnoid block, and intrathecal block: injection into the intrathecal space

    Neuraxial Analgesia vs Anesthesia

    • Anesthesia implies intense sensory and motor blockade
    • Analgesia implies sensory blockade only
    • Analgesia preferred for postoperative pain management or labor analgesia

    Advantages of Neuraxial Anesthesia

    • Reduced metabolic stress response to surgery
    • Significant blood loss reduction compared to general anesthesia
    • Decreased incidence of venous thromboembolic complications
    • Reduced pulmonary compromise
    • Airway manipulation usually avoided
    • Mental status remains intact
    • Lower total systemic drug dose
    • Motor blockade from spinal avoids the need for muscle relaxant medications
    • Lower incidence of anesthesia-induced postoperative nausea and vomiting
    • Improved pain control with minimal systemic opioids

    Spinal vs Epidural Anesthesia

    • Spinal: punctures dura and injects local anesthetic into cerebrospinal fluid (CSF)
    • Epidural: requires 10-fold increase in dose of local anesthetic to fill epidural space
    • Spinal: rapid onset, dense blockade, predictable
    • Epidural: slower onset, less dense blockade, segmental

    Advantages of Spinal Anesthesia

    • Quick onset
    • More predictable block density
    • Less risk for block "patchiness" or unilateral block
    • Lower volume of local anesthetic required

    Disadvantages of Spinal Anesthesia

    • More immediate and dramatic hemodynamic changes
    • Not easily titratable
    • No ability to provide continued neuraxial analgesia
    • Block level cannot be augmented or modified

    Assessing Patients for Neuraxial Anesthesia

    • History includes: previous back injury or surgery, neurological symptoms or history of neurological diseases, bleeding tendencies, anticoagulation medication
    • Physical examination includes: neurological exam, back exam, cardiovascular exam
    • Surgery specific factors: expected duration, blood loss, positioning required, need for muscle relaxation
    • General information: explanation of procedure, risks, benefits, options, desire for sedation

    Epidural Space

    • Lies just outside the dural sac containing the spinal cord and CSF
    • Structures traversed from superficial to deep: skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space
    • Widest point at L2
    • Contains fat, lymphatics, and an extensive venous plexus (Batson plexus)
    • Wraps 360 degrees around the dural membrane

    Lumbar Epidural Anesthesia

    • Ensure resuscitation equipment is available: oxygen, ventilation equipment, vasoactive medications
    • Monitor patient with pulse oximeter and blood pressure
    • Place IV line and consider fluid coload
    • Patient may be sitting or lying laterally
    • Visualize line between iliac crests to locate L4 spinous process
    • Palpate interspaces and choose the widest or the closest to the desired anesthetic level
    • Anesthesiologist and providers should be wearing protective gear
    • Prep/drape the site
    • Make a skin wheal with local anesthetic
    • Insert epidural needle in the midline
    • When there is initial resistance from ligaments, remove needle stylet and attach a syringe with air or saline
    • Advance several millimeters at a time, tapping the syringe
    • Ligamentum flavum is often described as leathery, gritty, or producing a marked increase in resistance
    • When the needle passes through ligamentum flavum and enters the epidural space, there is often a pop or give, and the air or fluid in the syringe injects easily
    • Thread catheter about 5 cm into the epidural space
    • Withdraw the epidural needle carefully
    • Aspirate for blood or CSF, if negative, give a test dose
    • Secure catheter in place

    Paramedian Epidural Placement Technique

    • Identify spinous process at desired interspace level
    • Use local anesthetic to create a skin wheal lateral to spinous process
    • Insert epidural needle perpendicular to skin until transverse process is encountered
    • Walk the needle off the transverse process, moving superiorly and medially
    • Advance until loss of resistance is achieved
    • Useful at high thoracic levels or when spaces between spinous processes are small

    Caudal Anesthesia

    • Form of epidural anesthesia where injection is made at the sacral hiatus (S5)
    • Accidental spinal injection is rare because the dural sac normally ends at S2
    • Limited use in adults due to variable sacral anatomy, calcification/ossification of ligaments, risk of injection into venous plexus, difficulty in maintaining sterility
    • Used primarily in children for postoperative analgesia

    Combined Spinal-Epidural Anesthesia

    • Performed by passing a long spinal needle through an epidural needle placed into the epidural space
    • Dura is punctured and CSF in the spinal needle acts as a confirmation of epidural needle placement
    • Combined spinal-epidural (CSE) uses the same technique, but additionally when CSF is confirmed in the spinal needle, a dose of local anesthetic with or without adjuvants is deposited in the subarachnoid space
    • Onset of block is markedly faster
    • Spinal needle is removed after injection and the epidural catheter is placed
    • Combines the advantages of both spinal and epidural anesthesia
    • Only performed in lumbar area

    Physiological Changes After Epidural Anesthesia

    • Decrease in blood pressure
    • Changes in heart rate: tachycardia or bradycardia may occur
    • Ventilatory changes: ventilation maintained as long as diaphragm is not impaired, but patients may become subjectively dyspneic
    • Bladder distention: sympathetic blockade and loss of sensation may result in bladder atony
    • Change in thermoregulation
    • Neuroendocrine changes: neural blockade above T8 blocks sympathetic afferents to the adrenal medulla

    Common Local Anesthetics for Epidural Anesthesia

    • Lidocaine 5% in dextrose
    • Bupivacaine 0.75% in dextrose
    • Ropivacaine 0.25%–1%
    • Tetracaine 1% in dextrose
    • Ropivacaine 0.5% in dextrose
    • Levobupivacaine 0.5%

    Structures Trespassed During Intrathecal Anesthesia

    • Structures: skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, dura mater, arachnoid membrane

    Bony Structures During Intrathecal Anesthesia

    • Shallow osseous tissue is likely spinous process
    • Deep osseous tissue is likely vertebral lamina

    Sites of Effect for Spinal Local Anesthetics

    • Sodium channels in spinal nerve roots and spinal cord

    Factors Determining Termination of Spinal Anesthesia

    • Dissociation of local anesthetic from nerve sodium channels
    • Resorption of agent from CSF into systemic circulation

    Factors Involved in Spinal Blockade Distribution

    • Patient characteristics: height, position, intraabdominal pressure, anatomic configuration of spinal canal, pregnancy
    • Total injected milligram dose of local anesthetic
    • Baricity of local anesthetic solution: hyperbaric, isobaric, hypobaric
    • Patient position during and after intrathecal injection

    Spinal Anesthesia Levels

    • Selected level should be below L1 in an adult, and L3 in a child
    • L3–L4 interspace is thought to be located at the line intersecting the top of the iliac crests

    Common Doses and Regimens for Spinal Anesthesia

    • Chloroprocaine: 3%, rapid onset, 45 minutes duration
    • Lidocaine: 2%, immediate onset, 60–90 minutes duration
    • Bupivacaine: 0.75%, slow onset, 2–3 hours duration
    • Ropivacaine: 0.75%, slow onset, 2–3 hours duration

    Complications of Neuraxial Anesthesia

    • Headache
    • Back pain
    • Nerve damage
    • Bleeding
    • Infection
    • Hypotension
    • Bradycardia
    • Respiratory problems
    • Nausea and vomiting

    Neuraxial Complications

    • Hypotension: A common complication, often secondary to sympatholysis
    • Causes: Fluid status, cardiac function, position changes
    • Treatments: Vasopressors
    • Safe Practices: Fluid preloading, careful positioning, incremental dosing
    • Risk Factors: Hypovolemia, age >40, sensory level >T5, low baseline BP, block at or above L3-L4
    • Bradycardia: Can occur due to unopposed vagal tone, blockade of cardioaccelerator fibers, or reflexes
    • Risk Factors: Increased vagal tone, high sympathectomy
    • Treatment: Atropine
    • Postdural Puncture Headache (PDPH): Caused by CSF leakage
    • Treatment: Epidural blood patch (EBP)
    • Transient Neurological Syndrome (TNS): Commonly associated with spinal lidocaine, results in buttocks pain radiating to the thighs and calves
    • Risk Factors: Lithotomy position, ambulatory surgery
    • Treatment: NSAIDs
    • Cauda Equina Syndrome: A rare but serious complication. Caused by compression of the cauda equina nerve roots
    • Nerve Injury: Can occur due to needle placement
    • Meningitis: A rare but serious complication
    • High/Total Spinal Anesthesia: Caused by too much anesthetic
    • Spinal Hematoma/Abscess Formation

    Neuraxial Anesthesia Considerations

    • General Anesthesia: Patients may require less general anesthetic due to neuraxial anesthetic's depressive effects
    • Monitoring: Close monitoring for hypotension and bradycardia is necessary, with potential for aggressive fluid resuscitation and vasopressor support
    • Fluid Preloading: Not always effective in preventing hypotension, but can be helpful in hypovolemic patients
    • Local Anesthetic Choice: Consider onset, duration, safety profile, and patient characteristics
    • Epinephrine: Added to local anesthetics to improve analgesia and reduce systemic absorption
    • Opioids: Can be added to neuraxial anesthesia to prolong analgesia
      • Lipophilic: Fentanyl and sufentanil
      • Hydrophilic: Morphine
    • Motor Blockade: Can be controlled by adjusting anesthetic concentration and type.
    • Anticoagulation: Neuraxial procedures can be performed in patients on anticoagulation if done carefully.
    • LMWH: Wait at least 12 hours after prophylactic dose, 24 hours for other regimens
    • Heparin: Wait 4-6 hours with proven PTT normalization
    • Segmental Block: Epidural anesthesia is segmental, with the block most intense near the catheter insertion site and diminishing with distance.
    • Continuous Spinal Anesthesia: Safe and effective technique, useful for elderly or high-risk patients.
    • Enhanced Recovery After Surgery (ERAS): Emphasizes regional anesthesia, including neuraxial techniques, to minimize systemic opioid use.
    • Postoperative Assessment: Assess for residual blockade, headache, back pain, and side effects
    • Key Points:
      • Neuraxial anesthesia can decrease the minimal alveolar anesthetic concentration (MAC)
      • Close monitoring is essential for potential hypotension and bradycardia
      • PDPH should be closely monitored and treated with EBP
      • TNS is characterized by pain in the buttocks and lower extremities, with no objective neurological findings.
      • Epidural anesthesia is segmental, with the block strongest near the catheter or needle insertion point
      • ERAS utilizes regional anesthesia to reduce opioid use

    Peripheral Nerve Block Considerations

    • Indications: For anesthesia or analgesia
    • Anesthesia: Can avoid general anesthesia and periprocedural pain medication
    • Analgesia: Can avoid postoperative opioids and their side effects
    • Contraindications:
      • Anticoagulation
      • Peripheral neuropathy
      • Systemic infection
    • Trauma: May mask a compartment syndrome
    • Types of Blocks: Interscalene, supraclavicular, infraclavicular, axillary, individual nerve blocks
    • Upper Extremity Procedures:
      • Interscalene: Shoulder, distal clavicle, proximal humerus
      • Supraclavicular: Procedures below the shoulder
      • Infraclavicular: Procedures below the shoulder
      • Axillary: Procedures below the shoulder
    • Ultrasound Guidance: Essential for accurate placement and safety

    Brachial Plexus Nerve Blocks for Upper Extremity Surgery

    • Supraclavicular block provides anesthesia from below the deltoid to the fingers and can be effective for shoulder surgery depending on technique.
    • Supraclavicular block has approximately a 50% chance of phrenic nerve blockade and an increased risk of pneumothorax.
    • Ultrasound guidance is advised for supraclavicular blocks.
    • Infraclavicular block provides anesthesia from the mid-humerus to the fingers but can be more technically challenging due to the steep approach required.
    • Axillary block provides anesthesia from the mid-humerus to the fingers, often sparing the musculocutaneous nerve, which may require a separate block.
    • Axillary block requires the patient to abduct their arm.

    Supraclavicular Nerve Block Technique

    • Performed with the patient in a semi-sitting position with the head turned to the opposite side.
    • The arm is positioned at the ipsilateral lower extremity and the shoulder is externally rotated to depress the clavicle and increase space for the ultrasound probe.
    • The needle is advanced from lateral to medial and local anesthetic is deposited surrounding the divisions of the brachial plexus.
    • Care is taken to avoid traversing arteries as widespread variations in anatomy exist in the supraclavicular region.

    Infraclavicular Nerve Block Technique

    • Performed with the patient in the supine position.
    • The arm is positioned at the patient's side or above the head to elevate the clavicle for ultrasound probe access.
    • The probe is oriented cephalad to caudal at the level of the coracoid process.
    • The needle is advanced to the 6 o'clock position of the axillary artery and local anesthetic is deposited.
    • This block covers all three cords of the brachial plexus with one injection.
    • Achieving U-shaped spread on both sides of the artery is crucial to avoid sparing the medial or lateral cords.

    Axillary Nerve Block Technique

    • Performed while the patient's arm is abducted to 90 degrees.
    • The transducer is placed along the medial aspect of the arm in the axilla and the needle is traversed from cephalad to caudal to the 6 o'clock position of the axillary artery.
    • Multiple injections are often needed to achieve circumferential spread and anesthetize the median, ulnar, and radial nerves.
    • A separate needle insertion point to anesthetize the musculocutaneous nerve is often required for adequate distal forearm coverage.

    Risks of Brachial Plexus Blocks

    • Supraclavicular blocks have an increased risk of pneumothorax due to the block site being close to the pleura.
    • Supraclavicular blocks have a risk of intravascular injection in the subclavian artery and surrounding blood vessels.
    • Infraclavicular blocks carry an increased risk of intravascular injection due to the block's depth and steep insertion angle.
    • Axillary block is thought to have the lowest risk compared to other brachial plexus blocks.
    • If arterial puncture occurs during an axillary block, the axillary artery's superficial location allows for compression.

    Lower Extremity Nerve Blocks

    • Lower extremity blocks require multiple injections for complete coverage.
    • Lower extremity nerves are derived from the lumbar plexus (L1-L5) and the sacral plexus (L4-S3).
    • The lumbar plexus gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • The sacral plexus gives rise to the sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh.
    • Common lumbar plexus nerve blocks include the femoral and saphenous nerve blocks.
    • Common sacral plexus nerve blocks include the transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.

    Choosing Appropriate Lower Extremity Nerve Blocks

    • Consider the location of surgery, potential application of a tourniquet, and need for postoperative motor function when choosing a block.
    • Complete surgical anesthesia of the lower extremity requires a combination of sciatic and femoral blocks.
    • For ankle surgery, a popliteal sciatic and saphenous nerve block are needed.
    • For surgeries requiring a thigh tourniquet, a subgluteal sciatic and lumbar plexus block are necessary.
    • An ankle block is effective for surgery on the toes and forefoot.

    Lower Extremity Nerve Block Technique:

    • The lumbar plexus block is considered a deep block performed at a point 4-5 cm lateral to the L4-L5 interspace, approximated by the top of the iliac crest.
    • The lumbar plexus block is primarily performed with nerve stimulator guidance until quadriceps muscle contraction is elicited.
    • The lumbar plexus is located in the body of the psoas major muscle, typically 2 cm deep to the transverse process of the lumbar spine.
    • The femoral nerve block anesthetizes the anterolateral thigh and the medial skin below the knee.
    • With ultrasound guidance, the femoral nerve is visualized 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle.
    • The saphenous nerve is blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • The proximal sciatic nerve is found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur.
    • The subgluteal approach offers less technical challenge and is easier to visualize with ultrasound due to its location over the gluteus maximus tail.
    • The sciatic nerve is found posterior to the femur and posterolateral to the popliteal artery in the popliteal region.

    Risks of Lower Extremity Nerve Blocks

    • Lower extremity nerve blocks carry risks of nerve injury, intravascular injection, infection, and damage to surrounding structures.
    • Nerve injury is rare but can be caused by intraneural injection, ischemia, or local anesthetic toxicity.
    • Deep blocks, like lumbar plexus blocks, pose increased risks due to their depth and proximity to vulnerable structures.
    • Cases of aortic perforation, retroperitoneal hematoma, intrathecal injection, and bowel perforation have been reported.

    Plane vs Peripheral Nerve Blocks

    • Peripheral nerve blocks target specific nerves, while plane blocks target fascial planes where nerves reside.
    • Plane blocks use a higher volume of local anesthetic compared to peripheral nerve blocks.
    • The risk of direct nerve damage is reduced with plane blocks due to the absence of specific nerve targeting.

    Truncal Nerve Blocks

    • Truncal nerve blocks are used for thoracic, breast, and abdominal surgery.
    • Thoracic paravertebral blocks deposit local anesthetic in the paravertebral space where thoracic spinal nerves and the sympathetic trunk reside.
    • Thoracic paravertebral blocks result in unilateral anesthesia covering three to seven dermatomes of the abdomen or chest wall surrounding the insertion point.
    • Transversus abdominis plane (TAP) blocks are indicated for lower abdominal surgeries.
    • TAP blocks deposit local anesthetic in the plane between the internal oblique and transversus abdominis muscles.
    • TAP blocks anesthetize the lower anterior abdominal wall, including the groin.
    • The subcostal TAP approach can be used for upper abdominal blocks.
    • Bilateral blocks can be used for midline surgeries, but care must be taken to avoid local anesthetic toxicity.

    Erector Spinae, PECS, Serratus Anterior, and Quadratus Lumborum Blocks

    • The erector spinae block involves injecting local anesthetic between the vertebral transverse process and the erector spinae muscles.
    • The erector spinae block blocks thoracic or lumbar spinal nerves, making it suitable for breast, chest, upper, and lower abdominal surgeries.
    • The PECS I block is performed between the pectoralis major and pectoralis minor muscles.
    • The PECS I block blocks the lateral and medial nerves, providing partial coverage for breast surgery.
    • The PECS II block is performed between the pectoralis minor and serratus anterior muscles.
    • The PECS II block blocks thoracic intercostal nerves and the long thoracic nerve.
    • The serratus anterior block is performed deep to the serratus anterior muscle.
    • The serratus anterior block blocks thoracic intercostal nerves, thoracodorsal, and long thoracic nerves.
    • The quadratus lumborum block is performed at the anterolateral border of the quadratus lumborum muscle.
    • The quadratus lumborum block blocks thoracic and lumbar spinal nerves, suitable for upper and lower abdominal surgeries.

    Risks of Common Truncal Nerve Blocks

    • Paravertebral blocks have a risk of pleural puncture and pneumothorax due to the proximity of the paravertebral space to the pleura.
    • Epidural spread is possible with paravertebral blocks, leading to unintended contralateral effects and hemodynamic changes.
    • TAP blocks have become safer with ultrasound implementation.
    • Rare complications include intraperitoneal injection and possible injury to abdominal viscera.

    Advantages and Disadvantages of Truncal Nerve Blocks

    • Paravertebral blocks are versatile, providing dense analgesia for truncal procedures, but are higher risk than other truncal blocks.
    • PECS and serratus anterior blocks provide equivalent analgesia for breast surgery with lower risks than paravertebral blocks.
    • PECS blocks block the pectoral nerves, which are not blocked by other techniques.
    • TAP blocks are easier to perform than paravertebral blocks and are lower risk.
    • The quadratus lumborum block covers more dermatomes per injection than the TAP block but cannot be performed in the supine position.
    • The erector spinae block is lower risk due to its distance from sensitive structures, but its benefits are not well described in the literature.

    Key Points: Peripheral Nerve and Trunk Blocks

    • Nerve blocks are used for anesthesia or analgesia and can avoid general anesthesia and periprocedural pain medication.
    • Upper extremity nerve blocks primarily involve blocking the brachial plexus at various anatomical locations.
    • Lower extremity nerves are derived from the lumbar and sacral plexus.
    • Increased use of ultrasound has led to novel truncal nerve blocks for regional anesthesia.

    Regional Anesthesia Indications and Contraindications

    • Indications:
      • Surgical anesthesia and/or intra- and postoperative analgesia for upper and lower limb, thoracic, abdominal, breast, and head and neck surgeries.
      • Common surgeries include orthopedic procedures, amputations, thoracotomies, laparotomies, arteriovenous fistula creations/revisions, and mastectomies.
    • Contraindications:
      • Patient refusal, sepsis/bacteremia, infection at injection site, preexisting neuropathy, and coagulopathy.

    Advantages and Disadvantages of Peripheral Nerve Blockade vs General Anesthesia

    • Advantages:
      • Useful when general anesthesia is undesirable.
      • Patients avoid pulmonary complications or hemodynamic instability.
      • Opioid-sparing effects are particularly useful for perioperative pain control.
      • Local anesthetic injection causes vasodilation, aiding in perfusion of flaps or extremities.
    • Disadvantages:
      • Requires patient cooperation, making it unsuitable for children or patients with high anxiety, developmental delay, altered mental status, or dementia.
      • Reports of inadequate sensory loss before surgical incision due to incomplete nerve block or insufficient time between block and incision.
      • Preoperative blocks may be inflexible if intraoperative findings change.

    Methods of Regional Anesthesia

    • Single Injection: Peripheral nerve blocks can be performed as a single injection.
    • Continuous Infusion: Peripheral nerve blocks can be performed as a continuous infusion via indwelling catheter.
    • Neuraxial Blockade: Performed as an injection into the subarachnoid space (spinal anesthesia) or as a continuous infusion into the epidural space.
    • IV Regional Anesthesia (Bier Block): Local anesthetic is injected intravenously into an extremity in the presence of an inflated tourniquet.

    Bier Block Technique

    • IV placed in the operative extremity.
    • Elevate extremity and exsanguinate the limb.
    • Inflate a double tourniquet.
    • Inject lidocaine (≤ 3 mg/kg) intravenously into the operative extremity.
    • Lower the extremity, remove the IV, and proceed with surgery while the patient breathes spontaneously with or without sedation.
    • Typically used for procedures lasting 30 to 45 minutes.

    Peripheral Nerve Block Techniques

    • Ultrasound Guided: Most common technique. Direct visualization of local anesthetic spread around neural structures or between muscle and/or fascial layers.
    • Nerve Stimulation: Can be used alone or with ultrasound, especially when anatomic structures are difficult to identify on ultrasound.
    • Anatomic Landmarks or Subcutaneous Infiltration: Field block.

    Ultrasound Guided Nerve Block Technique

    • Advantages:
      • Better visualization of anatomic structures, decreasing the incidence of complications.
      • Visualization of blood vessels to decrease the risk of bleeding and hematoma formation.
      • Visualization of the pleura to reduce the risk of pneumothorax.
      • Identification of anatomical variations to prevent incomplete spread of local anesthetic.
      • Visualization of nerves to ensure all neural structures are surrounded by local anesthetic.
    • Disadvantages:
      • Requires specialized and expensive equipment.

    Nerve Stimulator Technique

    • Uses:
      • Emits an electrical stimulus through an insulated block needle.
      • Needle is advanced until muscle twitching and/or paresthesias are elicited.
      • Confirmation of needle tip location.
    • Advantages:
      • Confirmation of needle tip location.
    • Disadvantages:
      • Possibility of unintentional nerve trauma.
      • Inability to identify variant anatomy.
      • Twitching can occur with direct muscle stimulation.
    • Common Use: In conjunction with ultrasound, particularly when ultrasound visualization is difficult.

    Sonographic Resolution

    • Axial Resolution: Number of planes along the axis of the ultrasound beam. Dependent on pulse wavelength and the number of cycles per pulse.
    • Lateral Resolution: Clarity between two adjacent structures visualized simultaneously. Improves as wave frequency increases and the ultrasound beam width decreases.
    • Temporal Resolution: Relates to dynamic structures, like pulsating vessels. Improves with increased ultrasound frame rate.

    Improving Visualization Under Ultrasound

    • Selecting Ultrasound Probe:
      • High frequency (10–13 MHz) for superficial structures.
      • Medium frequency (6–10 MHz) for medium-depth structures.
      • Low frequency (2–5 MHz) for deep structures.
    • Adjusting Ultrasound Picture:
      • Optimize the depth setting.
      • Confirm probe orientation.
      • Apply sufficient gel.
      • Adjust gain for brightness and time-gain compensation to improve image quality.
      • Use Doppler ultrasound to identify pulsating blood vessels or anesthetic spread.
    • In-Plane Needle Visualization:
      • Align the needle with the plane of the ultrasound beam. 
      • Visualize the needle tip before advancing.
      • Tilt the ultrasound probe to improve visualization.
      • Puncture the skin farther away from the probe to reach deeper structures.
      • Echogenic needles are easier to visualize.

    Paravertebral Space Boundaries

    • Posterior Border: Superior costotransverse ligament.
    • Anterolateral Border: Parietal pleura.
    • Medial Border: Vertebral bodies and intervertebral disks.
    • Contents: Thoracic spinal nerves and sympathetic trunk.

    Anterolateral Abdominal Muscles

    • Muscles (Superficial to Deep): External oblique, internal oblique, and transverse abdominis.
    • Innervation: Anterior rami of T7–L1.
    • Blocks Targeting this Area: Transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks.

    Brachial Plexus

    • Formation: C5–T1 nerve roots.
    • Subdivisions: Roots, trunks, divisions, cords, and branches.
    • Blocks Targeting this Area: Interscalene, supraclavicular, infraclavicular brachial plexus nerve blocks, axillary, and various forearm nerve blocks.

    Lumbar Plexus

    • Formation: T12–L4 nerve roots.
    • Branches: Ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Blocks Targeting this Area: Lumbar plexus, femoral, and fascia iliaca blocks.

    Sciatic Nerve Innervation

    • Innervated Area: Majority of the lower extremity, excluding the anterior thigh and medial calf.
    • Formation: L4–S3 nerve roots.
    • Branches: Tibial and common peroneal nerves.
    • Block Approaches: Proximal (anterior, transgluteal, subgluteal) or popliteal fossa. Branches can also be blocked at the ankle.

    Ankle Cutaneous Innervation

    • Nerves: Tibial, saphenous, deep peroneal, superficial peroneal, and sural.
    • Origin: All but the saphenous arise from the sciatic nerve. Saphenous arises from the femoral nerve.
    • Innervation:
      • Tibial: Most of the heel and plantar surface of the foot.
      • Saphenous: Medial aspect of the lower leg and ankle.
      • Superficial peroneal: Most of the dorsum of the foot.
      • Deep peroneal: Small area at the webspace between the great and second toes.
      • Sural: Lateral ankle.

    Complications of Regional Anesthesia

    • General: Bleeding, infection, intravascular or intraneural injection, allergic reactions, damage to adjacent structures, block failure.
    • Interscalene and Supraclavicular Blocks:
      • Phrenic nerve involvement leading to ipsilateral diaphragmatic paresis.
      • Sympathetic chain involvement leading to ipsilateral Horner syndrome.
      • Recurrent laryngeal nerve involvement leading to hoarseness.
    • Other Possible Complications: Subarachnoid or epidural injection, pneumothorax.

    Decreasing the Risk of Complications

    • Sterile Technique: Essential.
    • Patient Monitoring: Ensure appropriate monitoring.
    • Local Anesthetic Injection:
      • Inject in small increments (≤ 5 cc, at a rate of no more than 1 cc/s).
      • Aspirate before each injection.
      • Allow for one complete circulation time (about 15–30 seconds) after injecting 10 cc to assess for signs/symptoms of systemic toxicity.
      • Stop injecting and withdraw the needle slightly if the patient reports sharp pain or paresthesias.
    • Ultrasound Guided Blocks: Do not advance the needle unless the tip is visualized.
    • Nerve Stimulator Blocks: Do not inject local anesthetic if a twitch response is obtained below 0.3 mA.
    • Continuous Monitoring: Monitor patient closely for changes in hemodynamics or mental status.

    Common Local Anesthetics

    • Short Duration:
      • 2-chloroprocaine: Rapid metabolism by plasma cholinesterases.
    • Intermediate Duration:
      • Lidocaine: Frequently combined with epinephrine to extend duration.
      • Mepivacaine:
    • Long Duration:
      • Ropivacaine: Slower onset of action but longer duration.
      • Bupivacaine: Higher cardiotoxicity and more motor blockade than ropivacaine, but slightly longer duration.

    Local Anesthetic Additives

    • Vasoconstrictors: Epinephrine to lengthen duration and decrease systemic absorption.
    • Sodium Bicarbonate: Alkalinizes the pH of the local anesthetic solution, decreasing time to block onset.
    • Clonidine: Alpha-2 agonist with analgesic properties. Improves block quality and prolongs duration.
    • Dexamethasone and Dexmedetomidine: Thought to prolong block duration.

    Factors Affecting Local Anesthetic Onset and Duration

    • Onset:
      • Dependent on pKa. The closer the pKa is to the body’s pH, the quicker the onset.
      • Sodium bicarbonate is sometimes added to increase the amount of nonionized form and decrease the onset of action.
    • Duration:
      • Type of local anesthetic.
      • Presence or absence of a vasoconstrictor.
      • Lipid solubility and protein binding can also contribute to longer duration.
      • Vasoconstrictors like epinephrine may be added to keep the anesthetic localized to the tissue surrounding the target nerve.

    Local Anesthetic Systemic Toxicity (LAST)

    • Causes:
      • Perineural injection of large doses of local anesthetic.
      • Accidental intravascular, intrathecal, or epidural injection.
    • CNS Effects:
      • Excitatory Phase: Tinnitus, circumoral numbness, lightheadedness, altered mental status, tremors, and tonic-clonic seizures.
      • Depressive Phase: Respiratory depression, coma, and respiratory arrest.
    • Cardiovascular Effects:
      • Hypotension due to vasodilation.
      • Conduction disturbances.
      • Ventricular arrhythmias.
      • Direct myocardial depression leading to cardiac arrest.

    LAST Treatment

    • Treat cardiac arrest in the setting of LAST differently than cardiac arrest from other causes.

    Note: This summary excludes certain information like figures and tables from the source material. It is recommended to revisit the original text for complete details.

    Treatment Algorithm for LAST

    • Immediately discontinue administration of all local anesthetics
    • Call for help and a LAST rescue kit
    • Alert cardiopulmonary bypass team
    • Ventilate with 100% oxygen, placing advanced airway if necessary
    • Treat seizures with benzodiazepines
    • Consider lipid emulsion therapy promptly at the first sign of a severe LAST event
    • Treat hypotension and bradycardia
    • Start cardiopulmonary resuscitation if patient becomes pulseless
    • Continue monitoring 4 to 6 hours after a cardiovascular event or at least 2 hours after a limited CNS event
    • Epinephrine boluses should be reduced to 1 mcg/kg (or lower)
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers

    Intravenous Lipid Emulsion Dosing for LAST

    • Patients heavier than 70 kg should be administered 100 mL lipid emulsion 20% over 2 to 3 minutes, followed by an infusion of 200 to 250 mL over 15 to 20 minutes
    • Patients less than 70 kg should receive a 1.5 mL/kg bolus, followed by an infusion of 0.25 mL/kg/min ideal body weight
    • If after the discussed treatment the patient remains unstable, rebolus at the same dose as described earlier 1 to 2 times and double the infusion rate
    • Dosing measurements need not be exact, but should not exceed the maximum dose of 12 mL/kg

    Peripheral Nerve Block Use

    • Regional anesthesia is beneficial for patients in whom general anesthesia should be avoided or in whom pain may be difficult to control, including patients with severe cardiopulmonary disease, obstructive sleep apnea, postoperative nausea and vomiting, chronic pain, and substance abuse
    • Peripheral nerve blocks can provide anesthesia or analgesia
    • Anesthetic peripheral nerve block may allow a patient to avoid general anesthesia and periprocedural pain medication
    • Analgesic blocks avoid postoperative opioids and their associated side effects
    • Methods of delivering regional anesthesia include peripheral nerve single injections or catheters, intravenous (IV) regional techniques, or neuraxial blockade
    • Peripheral nerves can be localized using ultrasound, nerve stimulator, elicited paresthesias, or landmark techniques

    Peripheral Nerve Block Contraindications

    • Nerve blocks can be associated with postoperative nerve damage
    • Most common reason to avoid offering a patient a nerve block is anticoagulation
    • A peripheral neuropathy, such as symptomatic spinal stenosis or Guillain-Barré, may increase the risk
    • A successful nerve block after a traumatic injury can mask diagnosis of a compartment syndrome
    • If a patient has a systemic infection, placement of a nerve catheter can result in a perineural abscess

    Upper Extremity Nerve Blocks

    • Most upper extremity nerve blocks involve blocking the brachial plexus at different anatomic locations
    • Blocks of the upper extremity are named for their anatomic correlation for probe position or needle insertion
    • Interscalene, supraclavicular, infraclavicular, and axillary are the most common brachial plexus blocks
    • With increased use of ultrasound, the supraclavicular block has become the mainstay for procedures below the shoulder
    • Individualized radial, median, and ulnar nerve blocks can be performed under ultrasound guidance to offer analgesia to the hand and fingers, while allowing for continued gross motor function

    Brachial Plexus Block Suitability for Procedures

    • The interscalene brachial plexus block is most suitable for procedures on the shoulder, distal clavicle, and proximal humerus
    • Supraclavicular, infraclavicular, and axillary brachial plexus blocks are detailed in Table 69.1

    Supraclavicular, Infraclavicular, and Axillary Nerve Block Anatomy and Technique

    • The supraclavicular nerve block is typically performed in the semi-sitting position, with the head turned to the opposite side
    • The needle is advanced from lateral to medial and local anesthetic is deposited, surrounding the divisions of the brachial plexus, lateral to the subclavian artery
    • The infraclavicular nerve block is a deep block that has the added benefits of avoiding phrenic nerve paralysis and accommodation of peripheral nerve catheters
    • The probe is oriented cephalad to caudad at the level of the coracoid process
    • The needle is advanced, until it is at approximately the 6 o’clock position of the axillary artery, and local anesthetic is deposited
    • The axillary nerve block is performed with the patient’s arm is abducted to approximately 90 degrees
    • The transducer is placed along the medial aspect of the arm in the axilla and the needle is traversed from cephalad to caudad to the 6 o’clock position of the axillary artery

    Supraclavicular, Infraclavicular, and Axillary Nerve Block Risks

    • The supraclavicular nerve block has an increased risk of pneumothorax compared with the infraclavicular and axillary approaches
    • The infraclavicular nerve block carries an increased risk of intravascular injection
    • The axillary nerve block is thought to have the least amount of risk comparatively to the other brachial plexus blocks

    Addressing Complications with Supraclavicular Nerve Block

    • The most appropriate course of action is to do a neurologic examination to evaluate the motor and sensory function of the median, radial, and ulnar nerves
    • Most likely, there has been ulnar nerve sparing from inadequate block of the lower trunk
    • A supplementary rescue block can be performed to anesthetize this area
    • Another option would be to block the ulnar nerve more distally

    Lower Extremity Nerve Blocks

    • The lower extremity requires multiple injections for complete coverage
    • The nerves of the lower extremity are derived from the lumbar plexus (L1–L5) and the sacral plexus (L4–S3)
    • The lumbar plexus gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves
    • The sacral plexus gives rise to the sciatic nerve, as well as the superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh

    Lower Extremity Nerve Block Suitability for Procedures

    • Location of the surgery, possible application of a tourniquet, and need for postoperative motor function should all be considered with each block
    • To achieve complete surgical anesthesia of the lower extremity, a combination of sciatic and femoral blocks will need to be performed

    Lower Extremity Nerve Block Anatomy and Technique

    • The lumbar plexus block is considered a deep block
    • The femoral nerve block is a very popular block for anesthesia of the anterolateral thigh and the medial skin below the knee
    • The saphenous nerve, the largest cutaneous branch of the femoral, is located more distal in the lower extremity, and is often blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery
    • The proximal sciatic nerve is found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur
    • In the popliteal region, the sciatic nerve has a variable branchpoint into the common peroneal and tibial nerves

    Lower Extremity Nerve Block Risks

    • Risks of nerve blocks to the lower extremity include nerve injury, intravascular injection, infection, and damage to surrounding structures
    • Nerve injury is a rare and not completely understood phenomenon
    • Blocks, such as the lumbar plexus block, pose increased and unique risks because of the depth of the block and its proximity to several vulnerable structures
    • Cases of aortic perforation with retroperitoneal hematoma, intrathecal injection and even bowel perforation have been reported with this block

    Plane Block vs. Peripheral Nerve Block

    • In contrast with a standard peripheral nerve block, a plane block involves anatomy where no distinct nerve needs to be identified
    • With the increased use of ultrasound, new block techniques have been discovered that involve the infiltration of local anesthetic, in particular fascial planes, where various nerves are known to traverse

    Truncal Nerve Blocks

    • The thoracic paravertebral block involves depositing local anesthetic in the paravertebral space where the thoracic spinal nerves and sympathetic trunk reside
    • The transversus abdominis plane (TAP) block is indicated for lower abdominal surgeries
    • The popular TAP block results in unilateral anesthesia of the lower anterior abdominal wall, including the groin

    Nerves Blocked by Other Truncal Nerve Blocks

    • Increased use of ultrasound has resulted in many novel truncal blocks (Table 69.2)

    Common Truncal Nerve Block Risks

    • Paravertebral blocks have a few additional risks to the standard risks of peripheral nerve blocks
    • TAP blocks have become increasingly safe since the implementation of ultrasound

    Advantages and Disadvantages of Each Truncal Block

    • The paravertebral block is very versatile in that it can be used for nearly any truncal procedure
    • For breast surgery, the PECS or serratus anterior blocks are easier to perform and provide equivalent analgesia with lower potential risk
    • The TAP and quadratus lumborum abdominal blocks similarly are easier to perform than the paravertebral block and are lower risk
    • The erector spinae is a new block that can be used for all of the same indications as the paravertebral block### Nerve Blocks
    • Upper extremity nerve blocks target the brachial plexus, with variations based on anatomical insertion points.
    • The lumbar plexus (L1-L5) and sacral plexus (L4-S3) supply nerves to the lower extremity.
    • Common lumbar plexus blocks include femoral and saphenous nerve blocks.
    • Common sacral plexus blocks include sciatic, popliteal sciatic, and ankle blocks.
    • Ultrasound advancements have led to innovative truncal blocks in regional anesthesia.

    Neuraxial Anesthesia

    • This involves injecting anesthetics or analgesics into the spinal canal.
    • Epidural anesthesia targets the epidural space, either lumbar or thoracic region.
    • Caudal anesthesia involves injection into the sacral hiatus.
    • Spinal anesthesia (also known as spinal block, subarachnoid block, or intrathecal block) targets the intrathecal space.

    Analgesia vs. Anesthesia

    • Anesthesia indicates a profound sensory and motor blockade, often used for surgical procedures.
    • Analgesia implies sensory blockade only, commonly used for pain management after surgery or during childbirth.

    Advantages of Neuraxial Anesthesia over General Anesthesia

    • Reduced metabolic stress response to surgery and anesthesia.
    • Decreased blood loss, particularly in procedures like Cesarean sections or lower extremity orthopedic surgeries.
    • Reduced incidence of venous thromboembolic complications.
    • Possible reduction in pulmonary compromise, avoiding airway manipulation and aspiration risks.
    • Preserves mental status, unless sedation is applied.
    • Significantly lowers the total systemic drug dosage.
    • Spinal block avoids muscle relaxant medications needed for surgical manipulation, eliminating need for reversal agents.
    • Markedly reduces anesthesia-induced nausea and vomiting.
    • Improved pain control with minimal systemic opioid use, employing low-dose intrathecal morphine or continuous epidural anesthesia.

    Spinal vs. Epidural Anesthesia

    • Spinal anesthesia involves direct injection of local anesthetic into the cerebrospinal fluid (CSF), leading to rapid, dense, and predictable blockade.
    • Epidural anesthesia requires a larger dose of local anesthetic to fill the epidural space and penetrate nerve coverings, resulting in slower onset and less dense blockade.
    • Epidural anesthesia often produces a segmental effect, impacting a specific band of dermatomes.
    • Spinal anesthesia requires a smaller needle, has a predictable block density, and is less prone to "patchiness" or unilateral block.
    • Epidural anesthesia lacks a definitive endpoint during placement, unlike CSF flow in spinal anesthesia.
    • Lower volume of local anesthetic required in spinal anesthesia, eliminating risk of local anesthetic systemic toxicity (LAST).

    Disadvantages of Single-Shot Spinal Anesthesia

    • More immediate and dramatic hemodynamic changes observed.
    • Difficult to titrate the dosage.
    • Limited ability to provide continuous analgesia beyond the initial dose.
    • Inability to augment block intensity or duration when necessary.
    • Block level or dermatomal window cannot be modified after injection, unlike continuous epidural techniques.

    Assessing Patients Before Neuraxial Anesthesia

    • Review previous back injuries or surgeries, neurological symptoms, bleeding tendencies, anticoagulant or antiplatelet medication use, and prior regional anesthesia experiences.
    • Conduct a brief neurological examination, back examination for landmarks and abnormalities, and cardiovascular examination.
    • Consider the expected duration of surgery, potential blood loss, necessary positioning, need for muscle relaxation, and surgeon's preferences.
    • Provide a detailed explanation of the procedure, risks, benefits, and alternative options.
    • Discuss the patient's desire for sedation and laboratory tests as deemed necessary.
    • Imaging (MRI or CT) is generally not required unless specific intracranial or spinal abnormalities exist.

    Epidural Space Anatomy

    • The epidural space surrounds the dural sac containing the spinal cord and CSF.
    • From superficial to deep, the epidural needle traverses skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, spinal meninges, and CSF.
    • The epidural space has its widest point at L2, containing fat, lymphatics, and the Batson venous plexus.
    • It extends to the foramen magnum superiorly and the sacral hiatus caudally.

    Lumbar Epidural Anesthetic Technique

    • Ensure resuscitation equipment is readily available.
    • Monitor the patient using pulse oximetry and blood pressure cuff.
    • Establish an IV line and consider fluid preloading to counter hypotension.
    • Position the patient sitting or lying laterally, with aligned spinous processes.
    • Administer sedation as necessary.
    • Visualize the line between the iliac crests to locate the L4 spinous process.
    • Palpate the L2-L3, L3-L4, and L4-L5 interspaces, choosing the widest or closest to the desired anesthetic level.
    • Maintain sterile technique with proper attire and draping.
    • Create a skin wheal with local anesthetic at the insertion site.
    • Insert the epidural needle in the midline, feeling resistance from ligaments.
    • Advance the needle incrementally, tapping the syringe intermittently to gauge the layers.
    • Recognize the "give" and easier syringe injection when the needle enters the epidural space, marking loss of resistance.
    • Thread the catheter into the epidural space, ensuring the catheter is secured in place after needle withdrawal.
    • Aspirate for blood or CSF before administering a test dose.

    Paramedian Technique for Epidural Catheter Placement

    • Identify the target spinous process and create a skin wheal lateral to it.
    • Insert the needle perpendicular to the skin, encountering the transverse process.
    • Walk the needle off the transverse process superiorly and medially until engaging with the ligamentum flavum.
    • Advance the needle until loss of resistance is achieved.
    • This technique is beneficial at high thoracic levels and in patients with limited spine mobility.

    Caudal Anesthesia

    • A form of epidural anesthesia where injection occurs at the sacral hiatus (S5).
    • Less prone to accidental spinal injection due to the dural sac ending at S2.
    • Limited use in adults due to highly variable sacral anatomy, calcification/ossification, venous plexus risk, and sterilization challenges with catheters.
    • Primarily used in children for postoperative analgesia after herniorrhaphy or perineal procedures.

    Combined Spinal-Epidural (CSE) or Dural-Puncture Epidural (DPE)

    • Involves passing a long spinal needle through a placed epidural needle to puncture the dura.
    • Confirms epidural needle placement adjacent to the dura by the presence of CSF in the spinal needle.
    • CSE combines this technique with a direct injection of local anesthetic in the subarachnoid space, accelerating onset.
    • Both techniques offer advantages of spinal and epidural anesthesia, leading to a more reliable epidural catheter.
    • Limited to the lumbar area due to spinal cord entry risks at higher levels.

    Physiological Changes After Successful Epidural Anesthesia

    • Decreased blood pressure.
    • Heart rate changes, including tachycardia and bradycardia.
    • Ventilatory changes, potentially causing subjective dyspnea and impaired cough reflex.
    • Bladder distention, potentially requiring catheterization.
    • Altered thermoregulation.
    • Neuroendocrine changes, blocking the sympathetic stress response.

    Local Anesthetic Doses for Epidural Anesthesia

    • Refer to Table 71.1 for suggested dosages and durations of effect for common local anesthetics.

    Anatomical Structures Trespassed During Intrathecal Space Entry

    • From superficial to deep: skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, dura mater, arachnoid membrane.
    • Note that the dura mater and arachnoid are not trespassed during successful epidural placement.

    Boney Structures Encountered During Intrathecal Space Entry

    • Shallow osseous tissue indicates a spinous process, which may be walked off to access the subarachnoid space.
    • Deep osseous tissue typically signifies a vertebral lamina, suggesting the provider is off midline and needs to redirect.

    Principal Sites of Effect for Spinal Local Anesthetics

    • Sodium channels within the spinal nerve roots and spinal cord are the main targets of spinal local anesthetics.
    • There's often a slight difference in motor and sensory blockade levels due to variations in nerve root anatomy.

    Factors Determining Termination of Spinal Anesthesia Effect

    • Dissociation of the local anesthetic from nerve sodium channels and its resorption into systemic circulation determine the duration of action.

    Factors Involved in Distribution of Spinal Blockade

    • Patient characteristics such as height, position, intra-abdominal pressure, spinal canal anatomy, and pregnancy influence the extent of blockade.
    • Individual CSF volume variation exists, with correlations to height and blockade regression.
    • The total injected milligram dose, not the volume or concentration, is critical.
    • Baricity (density ratio of local anesthetic solution to CSF) plays a vital role.
    • Patient position and vertebral column curvature impact distribution based on injectate baricity.

    Lumbar Levels for Spinal Anesthetic Administration

    • The selected level should be below L1 in adults and L3 in children to avoid spinal cord trauma.
    • The L3-L4 interspace is often estimated at the line intersecting the top of the iliac crests but can be inaccurate.

    Spinal Anesthesia Dosing Regimens

    • Refer to Table 71.2 for common local anesthetics used in epidural anesthesia, their concentrations, onset, duration, maximum dose, and notes.

    Common Complications of Neuraxial Anesthesia

    • Hypotension (detailed discussion in Question 22).
    • Heart rate changes, including tachycardia and bradycardia (discussed in Question 23).
    • Ventilatory changes, potentially influencing respiratory distress and impaired cough reflex.
    • Bladder distention.
    • Altered thermoregulation.
    • Neuroendocrine changes, affecting the stress response.

    Neuraxial Anesthesia Complications

    • Hypotension, pruritis, nausea, vomiting, and postdural puncture headache (PDPH) are common complications.
    • Rare but serious complications include nerve injury, cauda equina syndrome, meningitis, high/total spinal anesthesia, and spinal hematoma/abscess formation.
    • Hypotension is associated with sympatholysis, which decreases arterial pressure and increases venous capacitance.
    • Factors that increase the incidence of hypotension include hypovolemia, age greater than 40 years, sensory level greater than T5, baseline systolic blood pressure below 120 mm Hg, and performance of the block at or above L3-L4.
    • Bradycardia can occur secondary to unopposed vagal tone, blockade of the cardioaccelerator fibers, and/or Bezold-Jarisch or reverse Bainbridge reflexes.
    • Transient Neurological Syndrome (TNS) is commonly associated with spinal lidocaine and presents with pain or dysesthesias in the buttocks radiating to the thighs and calves.
    • Local Anesthetic Choice: Bupivacaine is an alternative to lidocaine for ambulatory procedures due to its longer duration and reduced risk of TNS.
    • Epinephrine can be added to local anesthetics to reduce uptake into the bloodstream, improve analgesia and block quality, and identify intravascular injection.
    • Motor Blockade can be decreased by lowering the concentration of local anesthetic and choosing a local anesthetic with favorable sensory:motor dissociation.
    • Epidural Anesthesia is segmental, with the block being most intense near the site of catheter insertion and diminishing with distance.
    • Continuous Spinal Anesthesia is a safe and effective technique that allows for titration of local anesthetics to effect.
    • Enhanced Recovery After Surgery (ERAS) protocols often include neuraxial anesthesia/analgesia to minimize systemic opioid administration and improve patient outcomes.
    • Postoperative Assessment should include satisfaction with the anesthetic, regression of sensory/motor block, back pain, headache, adequacy of pain relief, and presence of side effects.

    Peripheral Nerve Blocks

    • Peripheral Nerve Blocks are generally performed for anesthesia or analgesia, offering benefits such as avoidance of general anesthesia and postoperative opioids.
    • Contraindications for peripheral nerve blocks include anticoagulation, peripheral neuropathy, traumatic injury (risk of masking compartment syndrome), and systemic infection.
    • Common Upper Extremity Blocks: Interscalene, supraclavicular, infraclavicular, and axillary brachial plexus blocks.
    • Block Choice: The interscalene brachial plexus block is suitable for procedures on the shoulder, distal clavicle, and proximal humerus. Other blocks are chosen based on the surgical site.
    • Radial, median, and ulnar nerve blocks can be performed under ultrasound guidance to provide analgesia to the hand and fingers.

    Brachial Plexus Nerve Blocks for Upper Extremity Surgery

    • Supraclavicular Block: Provides anesthesia from below the deltoid to the fingers, potentially effective for shoulder surgery depending on technique. 50% chance of phrenic nerve blockade. Ultrasound guidance is recommended to minimize risk of pneumothorax.
    • Infraclavicular Block: Provides anesthesia from the mid-humerus to the fingers, but can be technically challenging.
    • Axillary Block: Provides anesthesia from the mid-humerus to the fingers, but may spare the musculocutaneous nerve requiring separate blocking. The patient's arm must be abducted during the procedure.

    Risks of Brachial Plexus Nerve Blocks

    • Supraclavicular Block: High risk of pneumothorax due to block site proximity to the pleura. Ultrasound guidance mitigates this risk. Careful needle placement is crucial to avoid intravascular injections into the subclavian artery or surrounding vessels including the dorsal scapular and suprascapular arteries.
    • Infraclavicular Block: Increased risk of intravascular injection due to the deep block and steep angle of insertion, making needle visualization difficult. Aspiration before injection is vital to ensure the needle tip is not in the axillary artery or vein. It can be challenging to visualize small arteries and veins at lower depths.
    • Axillary Block: Considered to have the least risk of the brachial plexus blocks due to the compressibility of the axillary artery. Manual compression can help prevent hematoma formation if arterial puncture occurs.

    Lower Extremity Nerve Blocks

    • Lumbar Plexus: Delivers anesthesia to the anterolateral thigh and the medial skin below the knee. It is a deep block.
    • Femoral Nerve Block: A popular choice for anesthesia of the anterolateral thigh and the medial skin below the knee.
    • Saphenous Nerve Block: Blocks the largest cutaneous branch of the femoral nerve, located more distally in the lower extremity.
    • Sciatic Nerve Block: Can be performed via transgluteal, subgluteal, or popliteal approaches.
    • Ankle Block: Effective for toe and forefoot surgery, but hindfoot anesthesia is typically spared.

    Risks of Lower Extremity Nerve Blocks

    • Risks include nerve injury, intravascular injection, infection, and damage to surrounding structures.
    • Preexisting neuropathy increases the risk of nerve damage from intraneural injection, ischemia, or toxicity from local anesthetics.
    • Lumbar plexus blocks pose unique risks due to their depth and proximity to vital structures, including the aorta and bowel.

    Plane Block vs Peripheral Nerve Block

    • Plane Block: A local anesthetic is infiltrated in fascial planes rather than targeting specific nerves. This reduces the risk of direct nerve damage from the needle.
    • Peripheral Nerve Block: Targets specific nerves.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    • Thoracic Paravertebral Block: Provides three to seven dermatomes of unilateral anesthesia to the chest wall. Good choice for smaller thoracic, abdominal, or breast surgeries.
    • Transversus Abdominis Plane (TAP) Block: Indicated for lower abdominal surgeries, such as hysterectomy and hernia repair. Provides unilateral anesthesia of the lower anterior abdominal wall, including the groin.
    • Upper TAP Block: Can be used to block the upper abdomen.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    • Erector Spinae Block: Infiltrates the plane between the transverse process of the vertebra and the erector spinae muscles. Blocks thoracic and lumbar spinal nerves, providing anesthesia for breast, chest, upper and lower abdominal surgery depending on injection point. Less risk of direct injury or nerve threatening hematoma than the Paravertebral block due to it's location farther from sensitive structures.
    • PECS Block: Two types:
      • PECS I: Between pectoralis major and pectoralis minor, blocks lateral and medial pectoral nerves. Partial coverage for breast surgery.
      • PECS II: Between pectoralis minor and serratus anterior, blocks thoracic intercostal nerves and long thoracic nerve. Appropriate for breast surgery including axillary dissection.
    • ** Serratus Anterior Block:** Deep to the serratus anterior muscle, blocks thoracic intercostal nerves, thoracodorsal and long thoracic nerves. Indicated for hemi-thorax procedures including breast and thoracic surgery.
    • Quadratus Lumborum Block: Infiltrates the anterolateral border of the quadratus lumborum muscle, blocks thoracic/lumbar spinal nerves. Used for upper or lower abdominal surgeries.

    Risks of Common Truncal Nerve Blocks

    • Paravertebral block: Risk of pleural puncture, pneumothorax, epidural spread, and vagal reaction.
    • TAP block: Risk of intraperitoneal injection and possible abdominal viscera injury, though these complications are rare.

    Advantages and Disadvantages of Truncal Nerve Blocks

    • Paravertebral block: Versatile for trunical procedures, provides dense analgesia, but carries higher risk than other blocks.
    • PECS block: Simple to perform, equivalent analgesia to paravertebral block with lower risk, blocks pectoral nerves spared by other techniques.
    • TAP block: Easier and safer than paravertebral block, but limited dermatomal coverage.
    • Quadratus Lumborum block: Greater dermatomal coverage than TAP block, but more challenging to perform and cannot be performed in the supine position.
    • Erector Spinae Block: Lower risk than paravertebral block as it targets a plane farther from sensitive anatomical structures. Less effective analgesia than paravertebral block.

    Key Points

    • Nerve blocks are used for anesthesia and analgesia and offer an alternative to general anesthesia.
    • Many upper extremity nerve blocks involve blocking the brachial plexus at different anatomical locations.
    • The lower extremity nerves are derived from the lumbar (L1–L5) and sacral plexus (L4–S3).
    • Numerous truncal nerve blocks have emerged as a result of increased use of ultrasound for regional anesthesia procedures.

    Regional Anesthesia Overview

    • Indications: Surgical anesthesia, intra- and postoperative analgesia for upper and lower limb, thoracic, abdominal, breast, head and neck surgeries
    • Common Surgeries: Orthopedic procedures, amputations, thoracotomies, laparotomies, arteriovenous fistula creations/revisions, mastectomies
    • Contraindications: Patient refusal, sepsis/bacteremia, infection at injection site, preexisting neuropathy, coagulopathy

    Advantages and Disadvantages of Regional Anesthesia

    • Advantages: Useful for patients with anticipated difficult airway or severe cardiopulmonary disease, opioid-sparing effects for patients with obstructive sleep apnea, severe postoperative nausea and vomiting, chronic opioid therapy, opioid abuse history or allergies to analgesics, aids in perfusion of compromised flaps or extremities
    • Disadvantages: Requires patient cooperation, may have inadequate sensory loss just before surgical incision, can be inflexible if intraoperative findings change

    Regional Anesthesia Delivery Methods

    • Single injection
    • Continuous infusion via indwelling catheter
    • IV Regional Anesthesia: Local anesthetic injected intravenously into an extremity in the presence of an inflated tourniquet.
    • Neuraxial Blockade: Injection into the subarachnoid space (spinal anesthesia) or continuous infusion into the epidural space.

    Bier Block Technique

    • IV is placed in the operative extremity.
    • Extremity is exsanguinated with a compression bandage.
    • Double tourniquet is inflated.
    • Lidocaine (≤ 3 mg/kg) is injected intravenously.
    • Extremity is lowered, IV is removed, and surgery proceeds.
    • Typically used for procedures lasting 30 to 45 minutes, as longer procedures are limited by tourniquet pain.

    Peripheral Nerve Block Techniques

    • Ultrasound Guidance: Direct visualization of local anesthetic spread around neural structures or between muscle and/or fascial layers
    • Nerve Stimulation: Used alone or with ultrasound, especially when anatomic structures are difficult to identify on ultrasound.
    • Anatomic Landmarks or Subcutaneous Infiltration: Field block.

    Ultrasound Guided Nerve Block Technique

    • In-plane (IP) Approach: Needle advanced in the plane of the ultrasound beam, entire needle shaft is visualized.
    • Out-of-plane (OP) Approach: Needle advanced perpendicular to the ultrasound beam, only a cross section of the needle is seen.
    • Advantages: Better visualization of anatomic structures, decreased incidence of certain complications, allows for visualization of blood vessels, pleura, anatomical variations, and nerves.
    • Disadvantages: Requires specialized and expensive equipment.

    Nerve Stimulator Technique

    • Technique: Nerve stimulator device emits electrical stimulus through an insulated block needle, needle is advanced until muscle twitching or paresthesias are elicited.
    • Advantages: Good confirmation of needle tip location.
    • Disadvantages: Possibility of unintentional nerve trauma, inability to identify variant anatomy, twitching can occur with direct muscle stimulation.
    • Most often used in conjunction with ultrasound.

    Sonographic Resolution

    • Axial: Number of planes along the axis of the ultrasound beam, dependent upon pulse wavelength and number of cycles per pulse.
    • Lateral: Clarity between two adjacent structures visualized simultaneously and located the same distance from the probe, improves as wave frequency increases and the ultrasound beam width decreases.
    • Temporal: Resolution of dynamic structures, improves with increased ultrasound frame rate.

    Optimizing Visualization Under Ultrasound

    • Select an appropriate frequency probe: High frequency for superficial structures, medium frequency for medium-depth structures, low frequency for deep structures.
    • Adjust depth and orientation of the probe.
    • Apply sufficient gel.
    • Adjust gain and time-gain compensation to reduce artifact.
    • Doppler ultrasound to identify pulsating blood vessels or spread of local anesthetic during injection.
    • For IP needle visualization, ensure the needle is aligned with the plane of the ultrasound beam.

    Paravertebral Space Boundaries

    • Posterior Border: Superior costotransverse ligament
    • Anterolateral Border: Parietal pleura
    • Medial Border: Vertebral bodies and intervertebral disks
    • Contents: Thoracic spinal nerves and sympathetic trunk

    Muscles of the Anterolateral Abdomen

    • Superficial to Deep: External oblique, internal oblique, transverse abdominis
    • Innervation: Anterior rami of T7–L1
    • Targeted Blocks: Transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks.

    Brachial Plexus

    • Formation: C5–T1 nerve roots.
    • Subdivisions: Roots, trunks, divisions, cords, branches.
    • Targeted Blocks: Interscalene, supraclavicular, infraclavicular brachial plexus nerve blocks, axillary, and various forearm nerve blocks.

    Lumbar Plexus

    • Formation: T12–L4 nerve roots
    • Branches: Ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • Targeted Blocks: Lumbar plexus, femoral, and fascia iliaca blocks.

    Sciatic Nerve

    • Innervation: Majority of the lower extremity, excluding the anterior thigh and the medial calf.
    • Nerve Roots: L4–S3
    • Branches: Tibial and the common peroneal nerves
    • Block Approaches: Proximally (anterior, transgluteal, subgluteal) or at the popliteal fossa; branches can be blocked at the ankle.

    Ankle Cutaneous Innervation

    • Cutaneous Innervation: Tibial, saphenous, deep peroneal, superficial peroneal, and sural nerves.
    • Tibial Nerve: Most of the heel and plantar surface of the foot.
    • Saphenous Nerve: Medial aspect of the lower leg and ankle.
    • Superficial Peroneal Nerve: Most of the dorsum of the foot.
    • Deep Peroneal Nerve: Small area at the webspace between the great and second toes.
    • Sural Nerve: Lateral ankle.

    Regional Anesthesia Complications

    • Bleeding
    • Infection
    • Intravascular or intraneural injection: LAST or nerve damage
    • Allergic reactions
    • Damage to adjacent structures
    • Block failure
    • Interscalene and Supraclavicular Blocks: Phrenic nerve involvement (ipsilateral diaphragmatic paresis), sympathetic chain involvement (ipsilateral Horner syndrome), recurrent laryngeal nerve involvement (hoarseness), subarachnoid or epidural injection, pneumothorax.

    Reducing Complications

    • Sterile technique
    • Appropriate monitoring
    • Inject local anesthetic in small increments (≤ 5 cc, at a rate of no more than 1 cc/s), aspirating before each injection.
    • Allow for one complete circulation time (about 15–30 seconds) after injecting 10 cc to assess for signs/symptoms of systemic toxicity.
    • Stop injecting and withdraw the needle slightly if the patient reports sharp pain or paresthesias.
    • Do not advance the needle unless the tip is visualized for ultrasound-guided blocks.
    • Do not inject local anesthetic if a twitch response is obtained below 0.3 mA for nerve stimulator blocks.
    • Continuously monitor the patient for changes in hemodynamics or mental status.

    ### Commonly Used Local Anesthetics

    • 2-Chloroprocaine: Short-acting, duration of action lasting 1.5 to 2 hours. Rapid metabolism by plasma cholinesterases allows for administration of high concentrations.
    • Lidocaine: Intermediate-acting, 1–3 hours duration.
    • Mepivacaine: Intermediate-acting, 3–5 hours duration.
    • Ropivacaine: Long-acting, 6–24 hours duration, slower onset (15–30 minutes).
    • Bupivacaine: Long-acting, 6–30 hours duration, slower onset (15–30 minutes), higher cardiotoxicity and causes more motor blockade than ropivacaine.

    Additives to Local Anesthetics

    • Epinephrine: Vasoconstrictor to lengthen block duration and decrease systemic absorption, tachycardia and hypertension effects can indicate intravascular injection.
    • Sodium Bicarbonate: Alkalinizes the local anesthetic solution, decreases time to block onset.
    • Clonidine: Alpha-2 agonist with analgesic properties, may improve block quality and prolong duration.
    • Dexamethasone and Dexmedetomidine: Thought to prolong block duration.

    Local Anesthetic Onset and Potency

    • Onset of action: Depends on the pKa, the closer to the body’s pH, the quicker the onset.
    • Potency: Correlates with lipid solubility, lipid soluble local anesthetics require lower concentrations to achieve the same effect as less lipid soluble drugs.

    Factors Influencing Block Duration

    • Type of local anesthetic
    • Presence/absence of a vasoconstrictor
    • Lipid solubility and protein binding.
    • Certain local anesthetics have short (45–90 minutes), medium (90–180 minutes), and long (4–30 hours) durations of action.

    Local Anesthetic Systemic Toxicity (LAST)

    • Causes: Perineural injection of large doses of local anesthetic, accidental intravascular, intrathecal, or epidural injection.
    • Signs and Symptoms:
      • CNS: Excitatory phase (tinnitus, circumoral numbness, lightheadedness, altered mental status, tremors, tonic-clonic seizures), followed by a depressive phase (respiratory depression, coma, respiratory arrest).
      • Cardiovascular: Hypotension, conduction disturbances, ventricular arrhythmias, direct myocardial depression, cardiac arrest.

    ### LAST Treatment

    • Cardiac arrest: Treatment is different from cardiac arrest from other causes.

    Local Anesthetic Systemic Toxicity (LAST) Treatment

    • Stop administering all local anesthetics immediately.
    • Call for help and get a LAST rescue kit.
    • Alert cardiopulmonary bypass team.
    • Ventilate the patient with 100% oxygen and place an advanced airway if necessary.
    • Treat seizures with benzodiazepines.
    • Consider lipid emulsion therapy promptly at the first sign of a severe LAST event.
    • Propofol is not a suitable alternative to lipid emulsion therapy and can cause severe hypotension in an already unstable patient.
    • Treat hypotension and bradycardia.
    • Start cardiopulmonary resuscitation (CPR) if the patient becomes pulseless.
    • Continue monitoring for 4-6 hours after a cardiovascular event or at least 2 hours after a limited CNS event.
    • Reduce epinephrine boluses to 1 mcg/kg (or lower).
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers.

    Intravenous Lipid Emulsion Dosing for LAST

    • Patients over 70 kg should receive 100 mL of 20% lipid emulsion over 2-3 minutes, followed by an infusion of 200-250 mL over 15-20 minutes.
    • Patients under 70 kg should receive a 1.5 mL/kg bolus followed by an infusion of 0.25 mL/kg/min of ideal body weight.
    • If the patient remains unstable after treatment, rebolus with the same dose 1-2 times and double the infusion rate.
    • Dosing measurements can be flexible but should not exceed a maximum dose of 12 mL/kg.

    Indications for Regional Anesthesia

    • Regional anesthesia may be beneficial in patients who should avoid general anesthesia or those with difficult pain management.
    • Examples include patients with severe cardiopulmonary disease, obstructive sleep apnea, postoperative nausea and vomiting (PONV), chronic pain, and substance abuse.

    Types of Regional Anesthesia

    • Methods of delivering regional anesthesia include peripheral nerve single injections or catheters, intravenous (IV) regional techniques, or neuraxial blockade.

    Peripheral Nerve Localization

    • Peripheral nerves can be localized using ultrasound, nerve stimulator, elicited paresthesias, or landmark techniques.

    Peripheral Nerve Block Complications

    • Complications from nerve blocks include bleeding, infection, intravascular or intraneural injection, allergic reactions, local anesthetic systemic toxicity (LAST), and damage to adjacent structures.

    Peripheral Nerve Block Indications

    • Nerve blocks are performed for two major indications: anesthesia or analgesia.
    • Anesthetic peripheral nerve blocks may allow patients to avoid general anesthesia and periprocedural pain medication.
    • This is advantageous for patients with risk factors such as difficult airways or general anesthesia intolerance.
    • Analgesic blocks primarily aim to avoid postoperative opioids and their side effects.
    • Analgesic blocks can improve postoperative pain scores, increase patient satisfaction, decrease nausea, and reduce the likelihood of postoperative admission.

    Contraindications for Peripheral Nerve Blocks

    • Avoid offering nerve blocks to patients at high risk for postoperative nerve damage.
    • Anticoagulation is a common reason to avoid nerve blocks.
    • Patients with intrinsic or pharmacological coagulopathy are at increased risk for hematoma formation and subsequent nerve damage.
    • Peripheral neuropathy, like symptomatic spinal stenosis or Guillain-Barré, may increase the risk of nerve damage.
    • A successful nerve block after a traumatic injury could mask a compartment syndrome diagnosis, delaying critical treatment.
    • Systemic infections can lead to perineural abscesses if a nerve catheter is placed.

    Common Upper Extremity Nerve Blocks

    • Most upper extremity blocks involve blocking the brachial plexus at different anatomic locations.
    • Blocks are named after their anatomical location for probe position or needle insertion.
    • Interscalene, supraclavicular, infraclavicular, and axillary are the most common brachial plexus blocks.
    • Supraclavicular blocks have become the mainstay for procedures below the shoulder with increased ultrasound use.
    • Individualized radial, median, and ulnar nerve blocks can be performed under ultrasound guidance to provide analgesia to the hand and fingers while maintaining gross motor function.

    Choosing the Appropriate Brachial Plexus Block

    • The interscalene block is suitable for procedures on the shoulder, distal clavicle, and proximal humerus.
    • Supraclavicular, infraclavicular, and axillary brachial plexus blocks are detailed in the table and offer coverage for different areas.

    Brachial Plexus Blocks for Upper Extremity Surgery

    • Supraclavicular Block
      • Offers anesthesia from below the deltoid to the fingers.
      • Can be effective for shoulder surgery depending on the technique.
      • Approximately 50% chance of phrenic nerve blockade.
      • Increased risk of pneumothorax.
      • Ultrasound guidance is recommended.
    • Infraclavicular Block
      • Anesthesia from the mid-humerus to the fingers.
      • Can be more technically challenging as it requires a steep approach.
    • Axillary Block
      • Anesthesia from the mid-humerus to the fingers.
      • Frequently spares the musculocutaneous nerve, requiring it to be blocked separately.
      • Requires patient to abduct their arm.

    Supraclavicular, Infraclavicular, and Axillary Blocks: Anatomic Landmarks and Technique

    • Supraclavicular Block
      • Performed in the semi-sitting position with the head turned to the opposite side.
      • Elevate the clavicle by reaching the arm to the ipsilateral lower extremity and externally rotating the shoulder.
      • Advance the needle from lateral to medial and deposit local anesthetic surrounding the brachial plexus divisions, lateral to the subclavian artery.
      • Avoid traversing arteries due to anatomical variations in the supraclavicular region.
    • Infraclavicular Block
      • A deep block with the benefits of avoiding phrenic nerve paralysis and accommodating peripheral nerve catheters.
      • Performed with the patient supine, and the arm positioned either at the patient’s side or above the head to elevate the clavicle.
      • Orient the probe cephalad to caudad at the level of the coracoid process.
      • Advance the needle to the 6 o'clock position of the axillary artery and deposit local anesthetic.
      • Achieve a U-shaped spread to both sides of the artery to avoid sparing the medial or lateral cords.
    • Axillary Block
      • Performed with the patient’s arm abducted to 90 degrees.
      • Place the transducer along the medial aspect of the arm in the axilla.
      • Advance the needle cephalad to caudad to the 6 o'clock position of the axillary artery.
      • Multiple injections are often required for circumferential spread to anesthetize the median, ulnar, and radial nerves.
      • A separate needle insertion point may be needed to anesthetize the musculocutaneous nerve for adequate distal forearm coverage.

    Risks Associated with Supraclavicular, Infraclavicular, and Axillary Blocks

    • Supraclavicular Block
      • Increased risk of pneumothorax compared to the infraclavicular and axillary approaches due to proximity to the pleura.
      • Ultrasound guidance minimizes pneumothorax risk, but excellent needle tip visualization is necessary.
      • Avoid intravascular injection in the subclavian artery and surrounding vessels, such as the dorsal scapular and suprascapular arteries.
    • Infraclavicular Block
      • Increased risk of intravascular injection.
      • Deeper target site and steep angle of insertion make needle visualization challenging.
      • Aspiration before each injection is vital to ensure the tip is not in the axillary artery or adjacent vein.
      • Visualizing small arteries and veins is more challenging at lower depths.
    • Axillary Block
      • Generally considered lower risk compared to other brachial plexus blocks.
      • The axillary artery is compressible due to its superficial location, making manual compression a viable technique to prevent hematoma formation if arterial puncture occurs.

    Rescuing an Incomplete Supraclavicular Block

    • Perform a neurologic examination to assess motor and sensory function of the median, radial, and ulnar nerves.
    • Ulnar nerve sparing due to inadequate blockade of the lower trunk is a likely cause of pain in one finger.
    • This occurs due to insufficient local anesthetic in the "corner pocket" where the lower trunk is located.
    • A supplementary rescue block can be performed to anesthetize the area, but there is a theoretical increased risk of nerve damage with needle passage.
    • Blocking the ulnar nerve more distally is another option.

    Common Lower Extremity Nerve Blocks

    • The lower extremity requires multiple injections for complete coverage.
    • Nerves are derived from the lumbar plexus (L1–L5) and the sacral plexus (L4–S3).
    • The lower extremity is often referred to as being covered by the lumbosacral plexus due to the overlap.
    • The lumbar plexus forms the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
    • The lumbar plexus, femoral, and saphenous nerve blocks are most common.
    • The sacral plexus forms the sciatic nerve, as well as the superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh.
    • Transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks are most common.

    Choosing the Appropriate Lower Extremity Nerve Block

    • Consider the location of the surgery, possible application of a tourniquet, and need for postoperative motor function when choosing a block.
    • Complete surgical anesthesia of the lower extremity requires a combination of sciatic and femoral blocks.
    • For example, complete anesthesia of the ankle for operative fixation requires both a popliteal sciatic and saphenous nerve block.
    • However, this combination does not provide analgesia for thigh tourniquet pain.
    • A more proximal block, like a subgluteal sciatic and lumbar plexus, is necessary in these cases.
    • Ankle blocks are effective for surgery on the toes and forefoot, but the hindfoot is usually spared.

    Lower Extremity Nerve Block Techniques and Anatomic Landmarks

    • Lumbar Plexus Block
      • Considered a deep block.
      • Needle insertion point is 4-5 cm lateral to the L4-L5 interspace, approximated by the top of the iliac crest.
      • Primarily performed with nerve stimulator guidance until contraction of the quadriceps muscle is elicited.
      • The lumbar plexus is in the body of the psoas major muscle, typically 2 cm deep to the transverse process of the lumbar spine.
      • Needle insertion depth ranges from 6 to 8 cm depending on body habitus.
    • Femoral Nerve Block
      • Popular block for anesthetizing the anterolateral thigh and the medial skin below the knee.
      • Ultrasound guidance allows for visualization of the nerve 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle.
    • Saphenous Nerve Block
      • The largest cutaneous branch of the femoral nerve, located more distally.
      • Often blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • Sciatic Nerve Block
      • Located deep to the gluteus maximus, between the ischial tuberosity and greater trochanter of the femur.
      • Many variations of sciatic nerve block exist, but the subgluteal approach is often less technically challenging, easier to visualize by ultrasound due to its location over the thin tail of the gluteus maximus.
    • Popliteal Sciatic Nerve Block
      • The sciatic nerve branches into the common peroneal and tibial nerves in the popliteal region.
      • Ultrasound guidance locates the sciatic nerve posterior to the femur and posterolateral to the popliteal artery.
      • Muscle borders of the nerve include the semitendinosus and semimembranosus medially and the biceps femoris laterally.

    Risks of Lower Extremity Nerve Blocks

    • Nerve Injury
      • Rare and not fully understood.
      • Preexisting neuropathy is more common in the lower extremities, increasing the risk of nerve damage from intraneural injection, ischemia, or local anesthetic toxicity.
    • Intravascular Injection
    • Infection
    • Damage to Surrounding Structures
    • The lumbar plexus block poses unique risks due to its depth and proximity to vulnerable structures.
    • Cases of aortic perforation with retroperitoneal hematoma, intrathecal injection, and even bowel perforation have been reported with this block.

    Plane Blocks vs. Peripheral Nerve Blocks

    • Plane blocks involve anatomy where no distinct nerve needs to be identified, unlike standard peripheral nerve blocks.
    • Ultrasound guidance has led to new block techniques that involve infiltrating local anesthetic into specific fascial planes where various nerves are known to traverse.
    • This technique has created new blocks that provide analgesia to the abdomen, chest, and trunk.
    • Plane blocks typically require larger local anesthetic volumes than peripheral nerve blocks.
    • The risk of direct nerve damage from the needle is reduced because individual nerves are smaller or absent at the location of injection.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgeries

    • Thoracic Paravertebral Block
      • Deposited local anesthetic in the paravertebral space where thoracic spinal nerves and the sympathetic trunk reside.
      • Results in anesthesia of 3-7 dermatomes unilaterally to the abdomen or chest wall surrounding the insertion point.
      • Suitable for smaller thoracic, abdominal, or breast surgeries.
    • Transversus Abdominis Plane (TAP) Block
      • Indicated for lower abdominal surgeries, such as hysterectomy or hernia repair.
      • Local anesthetic is deposited in the fascial plane between the internal oblique and transversus abdominis muscles.
      • Anterior divisions of T10–L1 and ilihypogastric and ilioinguinal nerves lie in this plane.
      • Provides unilateral anesthesia of the lower anterior abdominal wall, including the groin.
      • The subcostal TAP approach can be used to block the upper abdomen.
      • Bilateral blocks can be used for midline surgeries, taking into account local anesthetic dosing limits to avoid toxicity.

    Nerves Blocked by Erector Spinae, PECS, Serratus Anterior, and Quadratus Lumborum Blocks

    • Erector Spinae Block
      • Plane of injection: Between the transverse process of the vertebra and the erector spinae muscles.
      • Nerves blocked: Thoracic/lumbar spinal nerves.
      • Surgical indications: Breast, chest, upper and lower abdominal surgery depending on injection point.
    • PECS I Block
      • Plane of injection: Between pectoralis major and pectoralis minor.
      • Nerves blocked: Lateral and medial pectoral nerves.
      • Surgical indications: Partial coverage for breast surgery.
    • PECS II Block
      • Plane of injection: Between pectoralis minor and serratus anterior.
      • Nerves blocked: Thoracic intercostal nerves and long thoracic nerve.
      • Surgical indications: Breast surgery including axillary dissection.
    • Serratus Anterior Block
      • Plane of injection: Deep to the serratus anterior muscle.
      • Nerves blocked: Thoracic intercostal nerves, thoracodorsal, and long thoracic nerves.
      • Surgical indications: Procedures of the hemi-thorax, including breast and thoracic surgery.
    • Quadratus Lumborum Block
      • Plane of injection: Anterolateral border of the quadratus lumborum muscle.
      • Nerves blocked: Thoracic/lumbar spinal nerves.
      • Surgical indications: Upper or lower abdominal surgeries.

    Risks of Common Truncal Nerve Blocks

    • Paravertebral Blocks
      • Have additional risks compared to standard peripheral nerve blocks.
      • Pleural puncture and injection, resulting in pneumothorax, is possible due to proximity to the pleura..
      • Epidural spread can lead to unintentional contralateral block effects and hemodynamic changes.
      • Vagal reactions are common.
    • TAP Blocks
      • Becoming increasingly safe with ultrasound guidance.
      • Rare serious complications, such as intraperitoneal injection and possible injury to abdominal viscera, are still possible.

    Advantages and Disadvantages of Truncal Nerve Blocks

    • Paravertebral Block
      • Versatile, suitable for various truncal procedures.
      • Provides dense analgesia, often effective for surgical anesthesia.
      • Higher risk than newer blocks due to its location.
    • PECS Blocks
      • Easier to perform than paravertebral blocks.
      • Equivalent analgesia with lower risk.
      • Block the pectoral nerves, which are spared by other techniques.
    • TAP and Quadratus Lumborum Blocks
      • Easier to perform than paravertebral blocks.
      • Lower risk.
    • Quadratus Lumborum Block
      • Covers more dermatomes per injection than TAP block
      • Cannot be performed supine and is more challenging than the TAP block.
    • Erector Spinae Block
      • Can be used for the same indications as paravertebral blocks.
      • Lower risk of direct injury or nerve threatening hematoma as it is further from sensitive structures.
      • Benefits are not well studied in the literature.
      • May provide less effective analgesia compared to paravertebral blocks.

    Key Points: Peripheral Nerve and Trunk Blocks

    • Nerve blocks are generally performed for two major indications: anesthesia or analgesia.
    • Nerve blocks may allow patients to avoid general anesthesia and periprocedural pain medication.

    Nerve blocks

    • Most upper extremity nerve blocks are named for their anatomic correlation
    • Lower extremity nerves are derived from lumbar and sacral plexuses
    • Most common lumbar plexus blocks are femoral and saphenous nerve blocks
    • Most common sacral plexus blocks are transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks
    • Increased use of ultrasound has resulted in many novel truncal blocks

    Neuraxial Anesthesia

    • Epidural anesthesia refers to injection of anesthetics or analgesics into the epidural space at either the lumbar or thoracic level
    • Caudal anesthesia refers to injection into the sacral hiatus
    • Spinal anesthesia, spinal block, subarachnoid block, and intrathecal block are all terms used interchangeably to describe injection into the intrathecal space

    Neuraxial Analgesia vs. Anesthesia

    • Anesthesia implies an intense sensory and motor blockade, which is necessary to perform a surgical procedure
    • Analgesia implies sensory blockade only, usually for postoperative pain management or labor analgesia

    Advantages of Neuraxial Anesthesia

    • Reduced metabolic stress response to surgery and anesthesia
    • Significant blood loss reduction
    • Decreased incidence of venous thromboembolic complications
    • Reduced pulmonary compromise
    • Mental status remains intact
    • Total systemic dose of drug(s) is markedly decreased
    • Markedly lower incidence of anesthesia-induced postoperative nausea and vomiting

    Spinal Anesthesia vs. Epidural Anesthesia

    • Spinal anesthetic is performed by puncturing the dura and injecting a small amount of local anesthetic directly into the cerebrospinal fluid (CSF), producing a rapid, dense, and predictable neural blockade
    • Epidural anesthetic requires a 10-fold increase in dose of local anesthetic to fill the epidural space and penetrate the nerve coverings

    Advantages of Spinal Anesthesia

    • Often quicker onset time from injection to adequate surgical blockade
    • More predictable block density, particularly regarding motor blockade
    • Less risk for block “patchiness” and/or unilateral block
    • Lower volume of local anesthesia required eliminates the risk of local anesthetic systemic toxicity (LAST)

    Disadvantages of Spinal Anesthesia

    • More immediate and dramatic hemodynamic changes often observed
    • Not easily titratable
    • No ability to provide continued neuraxial analgesia beyond initial dose
    • No ability to augment intensity or increase duration of blockade if inadequate
    • Block level or dermatomal window cannot be augmented or modified once set

    Assessing a Patient Before Neuraxial Anesthesia

    • History: previous back injury or surgery, neurological symptoms or history of neurological disease, bleeding tendencies or diseases associated with coagulopathy, anticoagulation or antiplatelet medication, prior regional anesthesia and any associated problems
    • Physical Examination: brief neurological examination for strength and sensation, back examination for landmarks and potential anatomic abnormalities or pathology, cardiovascular examination
    • Surgery Specific: expected duration, expected blood loss, positioning required, need for muscle relaxation, surgeon's preferences
    • General Information: patient should be given a detailed explanation of the procedure, risks, benefits, and options
    • Laboratory Tests: not globally required unless medical history or medications indicate possible coagulation disorder
    • Imaging: magnetic resonance imaging and/or computed tomography (CT) are not necessary except in case-by-case instances

    Epidural Space Anatomy

    • Epidural space lies just outside and envelops the dural sac containing the spinal cord and CSF
    • Epidural space has its widest point (5 mm) at L2
    • Epidural space contains fat, lymphatics, and venous plexus
    • The most anterior boundary of the epidural space is the posterior longitudinal ligament

    Lumbar Epidural Anesthetic Technique

    • Ensure that resuscitation equipment is immediately available
    • Monitor the patient with at least a pulse oximeter and blood pressure cuff
    • Place a well-running intravenous (IV) line
    • The patient may be sitting or lying laterally
    • For lumbar epidural placement, visualize a line between the iliac crests to locate the L4 spinous process
    • The anesthesiologist or anesthesia provider must wear a hat, mask, and sterile gloves and remove all jewelry
    • The site should be prepped/draped
    • A skin wheal is made with local anesthetic at the desired insertion site
    • Once initial resistance from ligaments is felt, remove the needle stylet and attach a syringe with 3 to 4 mL of air or saline
    • Advance several millimeters at a time, tapping the syringe intermittently
    • As the needle passes through ligamentum flavum and enters the epidural space, there is often a pop or give, and the air or fluid in the syringe injects easily; this marks the loss of resistance

    Paramedian Technique for Epidural Catheter Placement

    • Paramedian epidural placement starts by identifying the spinous process at the desired interspace level
    • Insert the epidural needle through the wheal perpendicular to the patient's skin, until the transverse process of the vertebra is encountered
    • Walk the epidural needle off the transverse process, moving superiorly and medially, until the needle is engaged in the ligamentum flavum
    • This approach is useful at high thoracic levels, where the spinous processes are acutely angled downward

    Caudal Anesthesia

    • Caudal anesthesia is a form of epidural anesthesia in which the injection is made at the sacral hiatus (S5)
    • Caudal anesthesia is used primarily in children to provide postoperative analgesia

    Combined Spinal-Epidural Anesthetic

    • A dural-puncture epidural (DPE) is performed by passing a long spinal needle through an epidural needle that has been placed into the epidural space
    • A combined spinal-epidural (CSE) is the same technique, but additionally when CSF is confirmed in the spinal needle, a dose of local anesthetic with or without adjuvants is deposited in the subarachnoid space
    • Either technique combines the advantages of both spinal and epidural anesthesia

    Physiological Changes After Successful Initiation

    • Decrease in blood pressure
    • Changes in heart rate: Tachycardia or Bradycardia
    • Ventilatory changes: Patients may become subjectively dyspneic as they become unable to feel their intercostal muscles, may experience significant respiratory distress with sedation
    • Bladder distention: Sympathetic blockade and loss of sensation, may require catheterization
    • Change in thermoregulation
    • Neuroendocrine changes: Neural blockade above T8 blocks sympathetic afferents to the adrenal medulla, inhibiting the neural component of the stress response

    Common Local Anesthetics Used in Epidural Anesthesia

    • Lidocaine
    • Bupivacaine
    • Ropivacaine
    • Tetracaine
    • Levobupivacaine

    Structures Trespassed When Entering Intrathecal Space

    • Skin, subcutaneous/adipose tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, dura mater, and arachnoid membrane

    Boney Structures Encountered

    • Shallow osseous tissue is likely spinous process
    • Deep osseous tissue tends to be vertebral lamina

    Sites of Effect of Spinal Local Anesthetics

    • Sodium channels in the spinal nerve roots and the spinal cord itself

    Termination of Effect of Spinal Anesthesia

    • Dissociation of the local anesthetic from nerve sodium channels and resorption of the agent from the CSF into the systemic circulation limits duration

    Factors Involved in Distribution (and Extent) of Spinal Blockade

    • Patient characteristics including height, position, intraabdominal pressure, anatomic configuration of the spinal canal, and pregnancy
    • Total injected milligram dose of local anesthetic is important
    • The baricity of the local anesthetic solution is important
    • Patient position during and after intrathecal injection and vertebral column curvature influence distribution in relation to baricity of injectate

    Lumbar Levels for Spinal Anesthetic Administration

    • Selected level should be below L1 in an adult, and L3 in a child, to avoid needle trauma to the spinal cord

    Common Doses and Dosing Regimens for Spinal Anesthesia

    • Chloroprocaine
    • Lidocaine
    • Bupivacaine
    • Ropivacaine

    Complication of Neuraxial Anesthesia

    • Hemodynamic changes: hypotension, bradycardia, tachycardia, cardiac arrest
    • Neurological complications: spinal headache, nerve injury, cauda equina syndrome, meningitis
    • Respiratory complications: respiratory depression, apnea
    • Other complications: gastrointestinal problems, allergic reactions, pain during and after procedure

    Neuraxial Anesthesia Complications

    • Hypotension is common, and can be caused by sympatholysis which decreases arterial pressure and increases venous capacitance.
    • Nausea and vomiting are often caused by hypotension and can be worsened by Trendelenburg positioning.
    • Postdural Puncture Headache (PDPH) is a common complication.
    • Rare and serious complications include nerve injury, cauda equina syndrome, meningitis, high/total spinal anesthesia, and spinal hematoma/abscess formation.
    • Local anesthetic toxicity (LAST) can occur with intravascular injection of large doses of local anesthetic. This can be prevented by negative aspiration, incremental dosing, and the use of epinephrine as an additive.
    • Epinephrine-induced tachycardia can indicate intravascular injection.

    Neuraxial Anesthesia: Hypotension

    • Causes include sympathectomy, baseline fluid status, cardiac function, and patient positioning.
    • Considerations include hypovolemia, age, sensory level, baseline systolic blood pressure, and block level.
    • Treatments include vasopressor infusion (e.g., phenylephrine).
    • Safe Practices include avoiding Trendelenburg position, considering baricity, and using unilateral block strategies.

    Neuraxial Anesthesia: Bradycardia

    • Etiologies include unopposed vagal tone, blockade of cardioaccelerator fibers, and Bezold-Jarisch/reverse Bainbridge reflex.
    • Risk Factors include increased vagal tone.
    • Prevention and Management include careful patient selection and monitoring.

    Neuraxial Anesthesia: Anticoagulation

    • Timing of neuraxial procedure is critical, with a minimum of 12 hours after prophylactic LMWH and 24 hours after other LMWH regimens.
    • Anti-Xa levels can be assessed, but no evidence supports interpretation for residual activity.

    Neuraxial Opioids

    • Benefits include intense visceral analgesia, prolonged sensory blockade, and minimal motor/sympathetic function effects.
    • Mechanisms involve opiate receptors in the spinal cord’s dorsal horn.
    • Side Effects include respiratory depression, nausea, vomiting, pruritus, and urinary retention.
    • Dosing is significantly lower compared to systemic administration.
    • Advantages include being an excellent option for patients intolerant to neuraxial local anesthesia.

    Transient Neurological Syndrome (TNS)

    • Presentation includes pain or dysesthesias in the buttocks radiating to the thighs and calves.
    • Characteristics include improvement with activity, worsening at night, and response to NSAIDs.
    • Incidence is approximately 15% and typically associated with lidocaine.
    • Risk Factors include lithotomy position and ambulatory surgery.
    • No association with dextrose, opioids, epinephrine, or block technique.
    • Pregnancy may be protective.

    Local Anesthetic Choice

    • Bupivacaine is an appropriate alternative to lidocaine for ambulatory procedures, providing prolonged sensory block.
    • Lidocaine is commonly used for obstetric procedures due to low TNS risk and improved time to discharge.
    • Factors to consider include onset, duration, safety profile, and clinical characteristics.

    Epinephrine in Local Anesthetics

    • Benefits include vasoconstriction, reducing uptake and toxicity; improved analgesia and block quality; and identification of intravascular injection.
    • Considerations include potential harm from epinephrine in patients with severe coronary disease.

    Motor Blockade

    • Reducing Motor Block can be achieved through lower local anesthetic concentrations, sensory-motor dissociative agents, and epidural opioids.
    • Bupivacaine and ropivacaine exhibit sensory-motor dissociation, making them popular for obstetric anesthesia.

    Level of Anesthesia for Different Procedures

    • Determining Level is based on the innervation of the surgical site.
    • Testing involves sensory level assessment before incision (e.g., Alis clamping).

    Segmental Block

    • Definition is a block with upper and lower levels.
    • Intensity is highest near catheter/needle insertion site and decreases with distance.
    • Placement should be as close to the surgical site as possible.

    Non-Surgical Indications for Neuraxial Anesthesia

    • Rib Fractures benefit from improved pulmonary mechanics.
    • Vascular Access Procedures can benefit from neuraxial anesthesia.
    • High Spinal Cord Injury patients benefit from reduced dysautonomia.
    • High-Risk Procedures can allow patients to remain awake, enabling early recognition of complications.

    Epidural Anesthesia: Local Anesthetic Dosing

    • Volume is the primary determinant of block extent.
    • Factors affecting spread include age, pregnancy, obesity, height, and spinal anatomy.

    Continuous Spinal Anesthesia

    • Technique involves using a microcatheter for local anesthetic infusion.
    • Safety is improved with appropriate technique and catheter size.
    • Advantages include titration to effect, reduced hypotension, and successful use in high-risk patients.

    Neuraxial Anesthesia and Enhanced Recovery After Surgery (ERAS)

    • Combined Anesthesia (neuraxial with general) is increasingly common to minimize opioid use and improve patient outcomes.
    • ERAS Protocols emphasize multimodal analgesia and neuraxial techniques.
    • Benefits include reduced opioid requirements, improved pain scores, increased patient satisfaction, and earlier discharge.

    Postoperative Assessment Following Neuraxial Anesthesia

    • Patient Satisfaction should be assessed and misunderstandings addressed.
    • Regression of Block should be evaluated to ensure safe ambulation and normal bowel/bladder function.
    • Back Pain should be evaluated for bruising, redness, or swelling.
    • Headache should be monitored, especially after accidental dural puncture.
    • Pain Control should be assessed for adequacy at rest and with movement.
    • Side Effects should be monitored and managed.

    Key Points: Neuraxial Anesthesia

    • Decreased MAC may lead to increased sensitivity to sedatives.
    • Dense Sympathectomy requires close monitoring, fluid resuscitation, and vasopressor support.
    • PDPH requires observation and EBP treatment.
    • TNS is suspected with lidocaine spinal anesthesia and presents with pain in the buttocks and lower extremities, but without objective neurological findings.
    • Epidural Anesthesia is segmental, with intensity decreasing with distance from the catheter/needle insertion site.
    • ERAS Protocols utilize regional anesthesia, including neuraxial techniques.

    Peripheral Nerve Blocks

    • Indications include anesthesia and analgesia.
    • Benefits include avoiding general anesthesia, minimizing periprocedural pain, and reducing opioid use.

    Patients Inappropriate for Peripheral Nerve Blocks

    • Anticoagulation increases hematoma and nerve damage risk.
    • Peripheral Neuropathy increases nerve damage risk.
    • Traumatic Injury can mask compartment syndrome.
    • Systemic Infection can lead to perineural abscess.

    Common Upper Extremity Nerve Blocks

    • Brachial Plexus Block types include interscalene, supraclavicular, infraclavicular, and axillary.
    • Individual Nerve Blocks (radial, median, ulnar) are performed under ultrasound guidance.

    Choosing a Brachial Plexus Block

    • Interscalene Block suitable for shoulder, distal clavicle, and proximal humerus procedures.
    • Supraclavicular, infraclavicular, and axillary blocks are suitable for procedures below the shoulder.

    Brachial Plexus Nerve Blocks

    • Supraclavicular block provides anesthesia from below the deltoid to the fingers.
      • Can be effective for shoulder surgery
      • Requires ultrasound guidance.
      • Risk of pneumothorax.
    • Infraclavicular block provides anesthesia from the mid-humerus to the fingers.
      • May be technically challenging due to the steep approach.
    • Axillary block provides anesthesia from the mid-humerus to the fingers.
      • Frequently spares the musculocutaneous nerve, requiring separate blocking.
      • Requires the patient to abduct their arm.

    Lower Extremity Nerve Blocks

    • The lower extremity nerve blocks require multiple injections for complete coverage.
    • Common lower extremity blocks include lumbar plexus, femoral, saphenous, transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.
    • Complete anesthesia of the lower extremity requires a combination of sciatic and femoral blocks.
    • Ankle block provides effective anesthesia for toes and forefoot but spares the hindfoot.

    Truncal Nerve Blocks

    • Truncal nerve blocks are on the forefront of regional anesthesia.
    • Thoracic paravertebral block provides unilateral anesthesia to the abdomen, or chest wall.
    • Transversus abdominis plane (TAP) block provides anesthesia to the anterior abdominal wall, including groin.
    • Erector spinae, PECS I and II, serratus anterior, and quadratus lumborum blocks are all novel techniques.

    Risks of Nerve Blocks

    • General risks include nerve injury, intravascular injection, infection, and damage to surrounding structures.
    • Preexisting neuropathy increases risk of nerve damage.
    • Lumbar plexus block poses increased risks such as aortic perforation, intrathecal injection, and bowel perforation.
    • Paravertebral blocks have risks including pleural puncture, pneumothorax, epidural spread, and vagal reactions.
    • TAP blocks are considered safe, but rarely, intraperitoneal injection and injury to abdominal viscera can occur.

    Regional Anesthesia: Indications and Contraindications

    • Indications: Surgical anesthesia and/or intra- and postoperative analgesia for various surgeries, including orthopedic procedures, amputations, thoracotomies, mastectomies, and others.
    • Contraindications: Patient refusal, sepsis/bacteremia, infection at injection site, preexisting neuropathy, and coagulopathy.

    Advantages and Disadvantages of Regional Anesthesia

    • Advantages: Useful when general anesthesia is undesirable, particularly for patients with difficult airways or severe cardiopulmonary disease. Opioid-sparing effects benefit patients with obstructive sleep apnea, severe postoperative nausea and vomiting, and other opioid-related conditions. Vasodilation from local anesthetic injection can improve perfusion in compromised flaps or extremities.
    • Disadvantages: Requires patient cooperation, making it unsuitable for children or patients with anxiety, developmental delays, or altered mental status. Incomplete sensory loss can occur, and blocks may prove inflexible if surgical plans change. Often performed in conjunction with general anesthesia.

    Methods of Regional Anesthesia

    • Peripheral nerve blocks: Can be performed as a single injection or continuous infusion via indwelling catheter.
    • Neuraxial block: Administered as an injection into the subarachnoid space (spinal anesthesia) or continuous infusion into the epidural space.
    • IV regional anesthesia (Bier block): Local anesthetic injected intravenously into an extremity in the presence of an inflated tourniquet.

    Bier Block Technique

    • IV access placed in the operative extremity.
    • Extremity elevated and exsanguinated using a compression bandage.
    • Double tourniquet inflated, and lidocaine (≤ 3 mg/kg) injected intravenously.
    • Extremity lowered, IV removed, and surgery can proceed with spontaneous breathing.
    • Suitable for procedures lasting 30-45 minutes.

    Techniques for Performing Peripheral Nerve Blocks

    • Ultrasound guidance: Allows real-time visualization of anesthetic spread around neural structures. Preferred approach for most blocks.
    • Nerve stimulation: Used alone or with ultrasound, particularly when anatomy is difficult to visualize. Emits electrical stimulus to evoke muscle twitching or paresthesias, indicating nerve proximity.
    • Anatomic landmark and subcutaneous infiltration: Field block technique.

    Ultrasound-Guided Nerve Block

    • In-plane (IP) approach: Needle advanced in the plane of the ultrasound beam, allowing visualization of entire needle shaft.
    • Out-of-plane (OP) approach: Needle advanced perpendicular to the beam, visualizing only a cross section of the needle.
    • Advantages: Improved visualization of structures, reduced risk of bleeding and pneumothorax, identification of anatomical variations.
    • Disadvantage: Requires specialized and expensive equipment.

    Nerve Stimulator Technique

    • Procedure: Electrical stimulus emitted through a needle. Muscle twitching or paresthesias confirm nerve proximity.
    • Advantages: Confirms needle tip location.
    • Disadvantages: Risk of nerve trauma, inability to identify variant anatomy, possible muscle stimulation mistaken for nerve stimulation. Often used with ultrasound.

    Sonographic Resolution

    • Axial resolution: Clarity between adjacent structures along the ultrasound beam's axis. Depends on pulse wavelength and cycle count.
    • Lateral resolution: Clarity between structures located the same distance from the probe. Improves with increased frequency and narrower beam width.
    • Temporal resolution: Clarity of dynamic structures like pulsating vessels. Improves with increased frame rate.

    Optimizing Ultrasound Visualization

    • Select appropriate probe frequency based on target nerve depth.
    • Adjust depth, orientation, and gel application.
    • Use time-gain compensation to minimize artifact and improve image quality.
    • Utilize Doppler ultrasound to identify vessels and anesthetic spread.
    • Ensure needle alignment for proper IP visualization.

    Paravertebral Space Boundaries

    • Posterior: Superior costotransverse ligament
    • Anterolateral: Parietal pleura
    • Medial: Vertebral bodies and intervertebral disks
    • Contents: Thoracic spinal nerves and sympathetic trunk

    Anterolateral Abdominal Muscles

    • Layers (superficial to deep): External oblique, internal oblique, transverse abdominis.
    • Innervation: Anterior rami of T7–L1
    • Blocks targeting this area: Transverse abdominus plane block, ilioinguinal, iliohypogastric, and quadratus lumborum blocks

    Brachial Plexus

    • Formation: C5–T1 nerve roots
    • Subdivisions: Roots, trunks, divisions, cords, and branches
    • Blocks targeting this area: Interscalene, supraclavicular, infraclavicular, axillary, and forearm nerve blocks

    Lumbar Plexus

    • Formation: T12–L4 nerve roots
    • Branches: Ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves
    • Blocks targeting this area: Lumbar plexus, femoral, and fascia iliaca blocks

    Sciatic Nerve

    • Innervation: Majority of lower extremity (except anterior thigh and medial calf).
    • Formation: L4–S3 nerve roots
    • Branches: Tibial and common peroneal nerves
    • Approaches: Proximal (anterior, transgluteal, subgluteal) or popliteal fossa.

    Ankle Cutaneous Innervation

    • Nerves: Tibial, saphenous, deep peroneal, superficial peroneal, and sural.
    • Tibial: Heel and plantar surface of foot.
    • Saphenous: Medial lower leg and ankle.
    • Superficial peroneal: Most of the dorsum of the foot.
    • Deep peroneal: Webspace between the great and second toes.
    • Sural: Lateral ankle.

    Complications of Regional Anesthesia

    • Bleeding: Hematoma formation.
    • Infection: At injection site.
    • Intravascular injection: Leads to LAST (local anesthetic systemic toxicity).
    • Intraneural injection: Causes nerve damage.
    • Allergic reactions: To local anesthetics.
    • Damage to adjacent structures: Pneumothorax, phrenic nerve involvement (diaphragmatic paresis), sympathetic chain involvement (Horner syndrome), and recurrent laryngeal nerve involvement (hoarseness).
    • Block failure: Inadequate anesthetic spread.

    Decreasing Complications

    • Sterile technique: Important to follow.
    • Appropriate monitoring: Essential.
    • Small increments of local anesthetic: Inject ≤ 5 cc at a rate of no more than 1 cc/s.
    • Aspirate before each injection: To ensure needle is not in a vessel.
    • Allow for circulation time: 15-30 seconds after injecting 10 cc to monitor for toxicity.
    • Stop injection if pain or paresthesias: Withdraw the needle slightly.

    Commonly Used Local Anesthetics

    • Short-acting: 2-Chloroprocaine (duration: 1.5-2 hours).
    • Intermediate-acting: Lidocaine (1-3 hours) and mepivacaine (3-5 hours).
    • Long-acting: Ropivacaine (6-24 hours) and bupivacaine (6-30 hours).

    Local Anesthetic Additives

    • Vasoconstrictors (epinephrine): Lengthens duration of block, decreases absorption, and can indicate intravascular injection.
    • Sodium bicarbonate: Alkalinizes pH, decreasing onset time.
    • Clonidine (alpha-2 agonist): Potential to improve block quality and duration.
    • Dexamethasone and dexmedetomidine: Also thought to prolong block duration.

    Factors Affecting Local Anesthetics

    • Onset of action: Depends on pKa (closer to body's pH = quicker onset).
    • Potency: Correlates with lipid solubility.
    • Duration of action: Type of anesthetic, vasoconstrictor presence, lipid solubility, and protein binding.

    Local Anesthetic Systemic Toxicity (LAST)

    • Cause: Excessive local anesthetic absorption.
    • Signs and symptoms: Excitatory phase (tinnitus, numbness, lightheadedness, tremors, seizures), depressive phase (respiratory depression, coma), and cardiovascular effects (hypotension, arrhythmias, myocardial depression).

    LAST Treatment

    • Cardiac arrest in LAST: Treated differently than other causes.

    Local Anesthetic Systemic Toxicity (LAST)

    • ASRA (American Society of Regional Anesthesia and Pain Medicine) recommends discontinuing local anesthetic administration immediately if LAST occurs.
    • Call for help and use a LAST rescue kit.
    • Alert the cardiopulmonary bypass team.
    • Ventilate with 100% oxygen, using an advanced airway if necessary.
    • Treat seizures with benzodiazepines.
    • Consider lipid emulsion therapy promptly for severe LAST events.
    • Proposition is not a suitable alternative to lipid emulsion therapy.
    • Treat hypotension and bradycardia.
    • Start cardiopulmonary resuscitation (CPR) if the patient becomes pulseless.
    • Monitor the patient for 4-6 hours after a cardiovascular event, or at least 2 hours after a limited CNS event.
    • Reduce epinephrine boluses to 1 mcg/kg or lower.
    • Avoid lidocaine, vasopressin, calcium channel blockers, and beta blockers.

    Lipid Emulsion Therapy Dosing

    • Patients exceeding 70 kg should receive a 100 mL lipid emulsion 20% bolus over 2-3 minutes, followed by an infusion of 200-250 mL over 15-20 minutes.
    • Patients under 70 kg should receive a 1.5 mL/kg bolus, followed by an infusion of 0.25 mL/kg/min ideal body weight.
    • Rebolus with the same dose if the patient remains unstable, up to 1-2 times, and double the infusion rate.
    • The maximum dose should not exceed 12 mL/kg.

    Peripheral Nerve Blocks

    • Regional anesthesia is beneficial for patients who cannot receive general anesthesia or have difficult pain management.
    • Examples of such patients include those with severe cardiopulmonary disease, obstructive sleep apnea, postoperative nausea and vomiting, chronic pain, and substance abuse.
    • Regional anesthesia can be administered through peripheral nerve injections or catheters, IV regional techniques, or neuraxial blockade.
    • Peripheral nerves can be localized using ultrasound, nerve stimulator, elicited paresthesias, or landmark techniques.
    • Complications include bleeding, infection, intravascular or intraneural injection, allergic reactions, LAST, and damage to adjacent structures.

    Upper Extremity Nerve Blocks

    • Brachial plexus blocks are primarily used for upper extremity procedures.
    • Common types include interscalene, supraclavicular, infraclavicular, and axillary blocks.
    • Ultrasound-guided supraclavicular blocks are preferred for procedures below the shoulder.
    • Individualized radial, median, and ulnar nerve blocks can be performed under ultrasound guidance for hand and finger analgesia.

    Choosing the Appropriate Brachial Plexus Block for Upper Extremity Procedures

    • Interscalene block: Suitable for procedures on the shoulder, distal clavicle, and proximal humerus.
    • Supraclavicular block: Effective for shoulder surgery depending on technique. About 50% chance of phrenic nerve blockade, increased risk of pneumothorax, and ultrasound guidance is advised.
    • Infraclavicular block: Effective for procedures from the mid-humerus to the fingers. Can be technically challenging due to the steep approach required.
    • Axillary block: Effective for procedures from the mid-humerus to the fingers. Frequently spares the musculocutaneous nerve, requiring separate blockage. The patient needs to abduct their arm.

    Anatomical Landmarks and Techniques for Upper Extremity Blocks

    • Supraclavicular block: Performed in the semi-sitting position, with the head turned to the opposite side. The arm is reached to the ipsilateral lower extremity with the shoulder externally rotated to depress the clavicle. The needle is advanced from lateral to medial to surround the brachial plexus divisions, lateral to the subclavian artery.
    • Infraclavicular block: Performed with the patient supine. The arm is positioned by the patient's side or above the head to elevate the clavicle. The probe is oriented cephalad to caudad at the level of the coracoid process. The needle is advanced to the 6 o'clock position of the axillary artery for local anesthetic deposition. This block covers all three cords of the brachial plexus.
    • Axillary block: Performed with the patient's arm abducted to 90 degrees. The transducer is placed along the medial aspect of the arm in the axilla. The needle is traversed from cephalad to caudad to the 6 o'clock position of the axillary artery. Multiple injections may be needed to achieve circumferential spread and anesthetize the median, ulnar, and radial nerves.

    Risks of Upper Extremity Blocks

    • Supraclavicular: Increased risk of pneumothorax due to proximity to the pleura. Visualization of the needle tip with ultrasound is crucial to minimize this risk. Ensure avoidance of intravascular injection into the subclavian artery, dorsal scapular artery, or suprascapular artery.
    • Infraclavicular: Increased risk of intravascular injection. The target site depth and steep angle of insertion make needle visualization difficult, requiring aspiration before each injection.
    • Axillary: Considered the lowest risk brachial plexus block. The axillary artery is compressible due to its superficial location, making manual compression a viable technique to prevent hematoma formation.

    Managing Complications with Supraclavicular Blocks

    • If a supraclavicular block results in arm motor block but the patient still feels pain in one finger, perform a neurologic exam to assess the median, radial, and ulnar nerves.
    • Ulnar nerve sparing may occur due to inadequate block of the lower trunk.
    • A supplementary rescue block can be performed to anesthetize the "corner pocket," but it carries a theoretical increased risk of nerve damage.
    • Distal ulnar nerve block can also be performed.

    Lower Extremity Nerve Blocks

    • Lower extremity nerve blocks require multiple injections for complete coverage.
    • Nerves originate from the lumbar plexus (L1-L5) and the sacral plexus (L4-S3), collectively known as the lumbosacral plexus.
    • Lumbar plexus: Gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves. The lumbar plexus, femoral, and saphenous nerve blocks are most common.
    • Sacral plexus: Gives rise to the sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh. The transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks are most common.

    Choosing the Appropriate Lower Extremity Block

    • Consider factors such as surgical location, possible tourniquet application, and need for postoperative motor function when selecting a block.
    • A combination of sciatic and femoral blocks is often required for complete surgical anesthesia of the lower extremity.
    • For instance, an ankle block requires both a popliteal sciatic and saphenous nerve block for complete anesthesia, but not for analgesia from a thigh tourniquet.
    • A subgluteal sciatic and lumbar plexus block are necessary for analgesia from a thigh tourniquet.
    • Ankle blocks are effective for surgery on the toes and forefoot, but usually spare the hindfoot.

    Anatomical Landmarks and Techniques for Lower Extremity Blocks

    • Lumbar plexus block: Considered a deep block. The needle insertion point is 4-5 cm lateral to the L4-L5 interspace, approximated by the top of the iliac crest. Nerve stimulator guidance is primarily used to elicit contraction of the quadriceps muscle.
    • Femoral nerve block: Popular block for anesthetizing the anterolateral thigh and medial skin below the knee. The nerve can be visualized with ultrasound 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle.
    • Saphenous nerve block: Located more distally in the lower extremity. Commonly blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • Sciatic nerve block: Found deep to the gluteus maximus, between the ischial tuberosity and greater trochanter of the femur. The subgluteal approach is often less technically challenging and easier to visualize using ultrasound.
    • Popliteal sciatic nerve block: Found posterior to the femur and posterolateral to the popliteal artery. The muscle borders include the semitendinosus and semimembranosus medially and the biceps femoris laterally.

    Risks of Lower Extremity Blocks

    • Nerve injury: A rare and not fully understood phenomenon. Preexisting neuropathy increases the risk of nerve damage from intraneural injection, ischemia, or local anesthetic toxicity.
    • Intravascular injection, infection, and damage to surrounding structures.
    • Lumbar plexus blocks: Pose increased risks due to their depth and proximity to vulnerable structures. Aortic perforation with retroperitoneal hematoma, intrathecal injection, and bowel perforation have been reported.

    Understanding Plane Blocks

    • Plane blocks involve anatomy where no distinct nerve needs to be identified.
    • Local anesthetic is infiltrated into specific fascial planes, where diverse nerves are known to traverse.
    • Used commonly for abdominal, chest, and trunk regions.
    • Often require larger volumes of local anesthetic compared to standard peripheral nerve blocks.
    • The risk of direct nerve damage is reduced due to the smaller or absent individual nerves at the injection site.

    Common Truncal Nerve Blocks

    • Thoracic paravertebral block: Involves local anesthetic deposition in the paravertebral space containing thoracic spinal nerves and the sympathetic trunk.
    • Provides 3-7 dermatomes of unilateral anesthesia to the abdomen or chest wall, suitable for smaller thoracic, abdominal, or breast surgeries.
    • Transversus abdominis plane (TAP) block: Indicated for lower abdominal surgeries, such as hysterectomy or hernia repair.
    • Local anesthetic is deposited in the fascial plane between the internal oblique and transversus abdominis muscles, anesthetizing the lower anterior abdominal wall.
    • Subcostal TAP approach can be used for the upper abdomen.
    • Erector spinae block: Involves local anesthetic injection between the transverse process of the vertebra and the erector spinae muscles. An effective block for thoracic or lumbar spinal nerves.
    • PECS I block: Involves injecting local anesthetic between the pectoralis major and pectoralis minor muscles, blocking the lateral and medial pectoral nerves.
    • PECS II block: Involves injecting local anesthetic between the pectoralis minor and serratus anterior muscles, blocking intercostal nerves and the long thoracic nerve.
    • Serratus anterior block: Involves injecting local anesthetic deep to the serratus anterior muscle, affecting the intercostal nerves, thoracodorsal, and long thoracic nerves.
    • Quadratus lumborum block: Involves injecting local anesthetic at the anterolateral border of the quadratus lumborum muscle, affecting thoracic/lumbar spinal nerves.

    Specific Risks of Truncal Nerve Blocks

    • Paravertebral blocks: Increased risk of pleural puncture and injection, leading to pneumothorax. Epidural spread can occur, resulting in unintended contralateral effects and hemodynamic changes. Vagal reactions are common.
    • TAP blocks: Less risk since the implementation of ultrasound. Rare but serious complications include intraperitoneal injection and possible injury to abdominal viscera.

    Advantages and Disadvantages of Truncal Nerve Blocks

    • Paravertebral block: Versatile for nearly any truncal procedure. Provides dense analgesia effective for surgical anesthesia. Higher risk compared to other truncal blocks.
    • PECS block: Easier to perform than the paravertebral block and provides equivalent analgesia with lower risk. Blocks pectoral nerves, which are spared by other techniques.
    • Serratus anterior block: Same advantages as the PECS block.
    • TAP block: Easier to perform than the paravertebral block and is lower risk.
    • Quadratus lumborum block: Covers more dermatomes per injection compared to the TAP block.
    • Erector spinae block: Easier to perform than the paravertebral block and involves less risk of direct injury or nerve-threatening hematoma. Less effective analgesia than the paravertebral block.

    Summarized Key Points

    • Nerve blocks are typically used for anesthesia or analgesia, allowing patients to avoid general anesthesia and periprocedural pain medication.
    • Regional anesthesia can be administered through peripheral nerve injections or catheters, IV regional techniques, or neuraxial blockade.
    • Nerve blocks can be categorized into upper extremity, lower extremity, and truncal blocks, each with specific anatomical landmarks and techniques.
    • Each block type has associated risks, including nerve injury, intravascular injection, infection, and damage to surrounding structures.
    • Plane blocks have emerged as an alternative to standard peripheral nerve blocks, targeting specific fascial planes.
    • The type of block chosen depends on the surgical procedure, patient factors, and potential complications.
    • Ultrasound guidance is essential for most nerve blocks to ensure accuracy and minimize risks.

    Overview of Nerve Blocks

    • The nerves of the upper and lower extremities are blocked at different anatomical locations.
    • Common blocks in the upper extremity include: brachial plexus blocks
    • Common blocks in the lower extremity include: lumbar plexus blocks, femoral blocks, and saphenous blocks.
    • The sacral plexus gives rise to sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and the posterior cutaneous nerve of the thigh.
    • Common blocks from the sacral plexus include: Transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.

    Neuraxial Anesthesia and Analgesia

    • Neuraxial anesthesia includes epidural, caudal, spinal, subarachnoid, and intrathecal blocks.
    • Epidural anesthesia involves injecting anesthetics or analgesics into the epidural space at the lumbar or thoracic level.
    • Caudal anesthesia involves injecting anesthetics into the sacral hiatus.
    • Spinal, subarachnoid, and intrathecal blocks all refer to injection into the intrathecal space.
    • Neuraxial analgesia provides sensory blockade for pain management, while neuraxial anesthesia provides intense sensory and motor blockade for surgery.
    • Dilute local anesthetic, epidural opioids, or a combination of these may be used for analgesia.
    • Analgesia may be preferred for postoperative pain management or labor analgesia.

    Advantages of Neuraxial Anesthesia

    • Reduced metabolic stress response to surgery and anesthesia.
    • Decreased blood loss compared to general anesthesia, particularly for surgeries like cesarean section and lower extremity orthopedic procedures.
    • Reduced incidence of venous thromboembolic complications.
    • Reduced risk of pulmonary compromise.
    • Avoidance of airway manipulation and loss of airway protection, benefiting those with difficult airways, severe reactive airway disease, or aspiration risk.
    • Mental status remains intact, unless the patient is sedated.
    • Markedly decreased total systemic drug dosage.
    • Spinal motor blockade eliminates the need for muscle relaxant medications, leading to less need for reversal medications.
    • Improved pain control with minimal or no systemic opioids using either low-dose intrathecal morphine or continuous epidural anesthesia in the lumbar or thoracic region as indicated.

    Spinal vs. Epidural Anesthesia

    • Spinal anesthesia:
      • Involves injecting a small amount of local anesthetic directly into the CSF, producing a rapid, dense, and predictable neural blockade.
      • Requires a smaller dose of local anesthetic.
      • Has a quicker onset and more predictable block density.
      • Has a lower risk of local anesthetic systemic toxicity.
    • Epidural anesthesia:
      • Involves injecting a larger amount of local anesthetic into the epidural space.
      • Requires a larger dose of local anesthetic compared to spinal anesthesia.
      • Has a slower onset and less dense blockade.
      • Produces a segmental anesthesia.

    Disadvantages of Spinal Anesthesia

    • More dramatic and immediate hemodynamic changes.
    • Not easily titratable.
    • Limited ability to provide continuous neuraxial analgesia beyond the initial dose.
    • Inadequate block intensity cannot be easily augmented or extended.
    • Block level or dermatomal window cannot be modified after the initial injection.

    Assessing Patients Before Neuraxial Anesthesia

    • Evaluate medical history for:
      • Previous back injury or surgery.
      • Neurological symptoms or history of neurological disease.
      • Bleeding tendencies or diseases associated with coagulopathy.
      • Anticoagulation or antiplatelet medication use.
      • Prior regional anesthesia experience and associated problems.
    • Conduct a physical examination, including:
      • Neurological assessment for strength and sensation.
      • Back examination for landmarks, abnormalities, and pathology.
      • Cardiovascular examination for murmurs and heart failure signs.
    • Assess surgical-specific considerations like:
      • Expected duration and blood loss.
      • Positioning required and need for muscle relaxation.
      • Surgeon's preferences.
    • Provide the patient with a thorough explanation of the procedure, risks, benefits, and other options.
    • Discuss the patient's desire for sedation and the extent of sedation needed.
    • Obtain laboratory tests as indicated, particularly if medical history or medications suggest a possible coagulation disorder.
    • Imaging may be necessary on a case-by-case basis for patients with intracranial or spinal abnormalities.

    Epidural Space Anatomy

    • The epidural space lies around the dural sac, containing the spinal cord and CSF.
    • The epidural space is widest at L2.
    • The epidural space contains fat, lymphatics, and a venous plexus.
    • The epidural space encircles the dural membrane, extending to the foramen magnum superiorly and the sacral hiatus caudally.
    • The posterior longitudinal ligament forms the most anterior boundary of the epidural space.
    • The epidural space can be accessed in the cervical, thoracic, lumbar, or sacral regions.
    • In pediatric patients, the caudal epidural approach is commonly used.

    Technique for Lumbar Epidural Anesthesia

    • Ensure resuscitation equipment is readily available for blood pressure changes.
    • Monitor the patient with a pulse oximeter and blood pressure cuff.
    • Place a well-running intravenous (IV) line and potentially an appropriate coload of fluid to counter hypotension.
    • Position the patient sitting or lying laterally.
    • Visualize a line between the iliac crests to locate the L4 spinous process.
    • Palpate the L2–L3, L3–L4, and L4–L5 interspaces and choose the widest or closest interspace to the desired anesthetic level.
    • Ensure that the anesthesiologist or anesthesia provider and all personnel wear appropriate attire, including a hat, mask, and sterile gloves.
    • Remove all jewelry, and prep/drape the site.
    • Create a skin wheal with local anesthetic at the desired insertion site.
    • Insert the epidural needle in the midline.
    • After initial resistance from ligaments, attach a syringe with air or saline to the needle.
    • Advance the needle several millimeters at a time, tapping the syringe intermittently to feel for resistance.
    • The ligamentum flavum is usually leathery or gritty, offering greater resistance.
    • When the needle passes through the ligamentum flavum and enters the epidural space, there is a pop or give, and the air or fluid injects easily, indicating loss of resistance.
    • Thread the catheter about 5 cm into the epidural space.
    • Withdraw the epidural needle carefully.
    • After attaching the injector port to the catheter, aspirate for blood or CSF. If clear, administer a test dose.
    • Secure the catheter in place.

    Paramedian Epidural Technique

    • The paramedian technique involves identifying the spinous process at the desired interspace level and creating a skin wheal 1 to 2 fingerbreadths lateral to this point.
    • Insert the epidural needle perpendicular to the patient's skin until the transverse process of the vertebra is encountered.
    • Walk the needle off the transverse process superiorly and medially (15–30 degrees) until the needle is engaged in the ligamentum flavum.
    • Attach a friction-free syringe and advance until loss of resistance is achieved.
    • It's useful at high thoracic levels (above T9–T10) where the spinous processes are angled downward.
    • It's also advantageous when interspinous spaces are small, such as in patients with limited mobility.

    Caudal Anesthesia

    • Caudal anesthesia is a type of epidural anesthesia where the injection is made at the sacral hiatus (S5).
    • Accidental spinal injection is rare with caudal anesthesia because the dural sac ends at S2.
    • The caudal approach provides dense sacral and lower lumbar block levels, but its use in adults is limited by factors like:
      • Variable sacral anatomy.
      • Calcification/ossification of the sacral ligaments.
      • Risk of injection into venous plexus.
      • Difficulty in maintaining sterility with catheterized approaches.
    • Caudal anesthesia is primarily used in children for postoperative analgesia after procedures like herniorrhaphy or perineal procedures.

    Combined Spinal-Epidural Anesthesia

    • Combined spinal-epidural (CSE) anesthesia involves passing a long spinal needle through an epidural needle placed in the epidural space.
    • The spinal needle punctures the dura, permitting CSF confirmation of epidural needle placement.
    • A dose of local anesthetic with or without adjuvants like opioids is injected intrathecally in CSE.
    • The spinal needle is removed after injection and the epidural catheter is placed.
    • This technique provides the advantages of both spinal and epidural anesthesia.
    • These techniques (CSE and DPE) are restricted to lumbar areas (below L1-L2 in adults and below L3 in children) due to the risk of spinal cord entry at higher levels.

    Physiological Changes Following Neuraxial Anesthesia

    • Blood Pressure Decrease:Detailed discussion in question 22.
    • Heart Rate Changes:
      • Tachycardia may occur as cardiac output increases to compensate for decreased systemic vascular resistance.
      • Bradycardia is discussed in question 23.
    • Ventilatory Changes:
      • In normal patients, ventilation is maintained as long as the diaphragm remains functional (phrenic nerve: C3–C5).
      • However, patients may feel subjectively dyspneic from impaired intercostal muscles.
      • Patients dependent on accessory muscles of respiration may experience respiratory distress with sedation.
      • Coughing and airway protection can also be compromised, even if ventilation is adequate.
      • Upper extremity weakness or speech changes signal a potentially high block with impending ventilatory failure.
    • Bladder Distension:
      • Sympathetic blockade and loss of sensation can lead to bladder atony, requiring catheterization.
      • Urinary retention is common, particularly with epidural placement above T9.
    • Thermoregulation Changes: See question 28.
    • Neuroendocrine Changes:
      • Neuraxial blockade above T8 blocks sympathetic afferents to the adrenal medulla, inhibiting the stress response.
      • This could result in better glucose regulation in diabetic patients.

    Dosing of Common Local Anesthetics

    • See table 71.1 for suggested doses and duration of effect for various local anesthetics.
    • Table 71.2 lists anesthetics used in epidural anesthesia for surgery.
    • See question 21 for common doses and dosing regimens for spinal anesthesia.

    Anatomical Structures Trespassed During Intrathecal Injection

    • Structures encountered from superficial to deep include:
      • Skin
      • Subcutaneous/adipose tissue
      • Supraspinous ligament
      • Interspinous ligament
      • Ligamentum flavum
      • Dura mater
      • Arachnoid membrane
    • Note that the dura mater and arachnoid are not trespassed in successful epidural placement.

    Boney Structures Encountered During Intrathecal Injection

    • Shallow osseous tissue is likely the spinous process, which may be walked off above or below to gain access to the subarachnoid space.
    • Deep osseous tissue, such as the vertebral lamina, indicates being off midline and a need to redirect the needle.

    Sites of Effect of Spinal Local Anesthetics

    • The primary sites of action are sodium channels in spinal nerve roots and the spinal cord itself.
    • Anatomic variations in nerve roots and rootlets can influence the spread of injected medications in the CSF, resulting in different motor and sensory blockade levels.

    Termination of Spinal Anesthesia Effect

    • The effect of spinal anesthesia is terminated by dissociation of the local anesthetic from nerve sodium channels and resorption of the agent into circulation.

    Distribution of Spinal Blockade

    • Patient characteristics like height, position, intra-abdominal pressure, spinal canal anatomy, and pregnancy can impact spinal blockade distribution.
    • Lumbosacral CSF volume varies, impacting the extent of blockade.
    • CSF volumes correlate well with height and regression of blockade.
    • Although CSF volumes are reduced during pregnancy, no external physical measurements can reliably estimate lumbar CSF volume.
    • The total milligram dose of local anesthetic is crucial, regardless of volume or concentration.
    • The baricity of the local anesthetic solution (density relative to CSF) is critical.
      • Hyperbaric solutions (greater than 1) tend to sink.
      • Isobaric solutions (equal to 1) stay at the injection site.
      • Hypobaric solutions (less than 1) rise in the CSF.
    • Patient position during and after injection and vertebral column curvature can also affect distribution.

    Lumbar Levels for Spinal Anesthesia

    • Spinal anesthesia should be administered below L1 in adults and below L3 in children to avoid needle trauma to the spinal cord.
    • The L3–L4 interspace is often used as a landmark, but its exact location correlates poorly with actual levels.

    Complications of Neuraxial Anesthesia

    • Hemodynamic changes

    • Heart rate changes

    • Ventilatory changes

    • Bladder distension

    • Thermoregulation changes

    • Neuroendocrine changes### Neuraxial Anesthesia Complications

    • Hypotension is a common complication, often caused by sympatholysis, especially with higher thoracic anesthetic levels

    • Treatment for hypotension includes vasopressor infusion (e.g., phenylephrine)

    • Fluid preloading does not reliably reduce the incidence of hypotension, but may be necessary in hypovolemic patients

    • Other risk factors for hypotension include age > 40 years, sensory level above T5, baseline systolic BP < 120 mmHg, and blocks performed at or above L3-L4

    • Nausea and vomiting may result from hypotension or decreased cerebral blood flow

    • Trendelenburg position following intrathecal injection can increase the level of blockade with hyperbaric spinal anesthesia, and should be used cautiously

    • Unilateral block with a hyperbaric injection followed by positioning the patient with the surgical side down may reduce hypotension

    • Bradycardia can occur due to increased vagal tone, blockade of cardioaccelerator fibers (T1-T4), or Bezold-Jarisch/reverse Bainbridge reflexes

    • Risk factors for bradycardia include increased vagal tone, high doses of neuraxial narcotics, and prior vagal tone modulation

    • Treatment for bradycardia includes observation, atropine, and potential need to discontinue neuraxial narcotics

    • Postdural puncture headache (PDPH) is a common, yet treatable, complication

    • Treatment for PDPH includes conservative measures (hydration, caffeine) and, if needed, an epidural blood patch

    • Transient neurological syndrome (TNS) includes pain or dysesthesia in the buttocks, radiating to the thighs and calves

    • Risk factors for TNS include lithotomy position and ambulatory surgery patients

    • Treatment for TNS is conservative, with NSAIDs

    • Nerve injury, cauda equina syndrome, meningitis, high/total spinal anesthesia, and spinal hematoma/abscess formation are rare, but more serious complications

    • Local anesthetic toxicity (LAST) can occur with intravascular injection of a large dose

    • Prevention of LAST includes negative aspiration, epinephrine addition, and incremental dosing

    • Epinephrine is often added to local anesthetics for improved analgesia, reduced absorption, and identifying intravascular injection

    • Spinal anesthesia has low risk of LAST due to low local anesthetic doses

    • Neuraxial opioids provide visceral analgesia and may prolong sensory blockade without affecting motor/sympathetic function

    • Lipophilic opioids (fentanyl, sufentanil) have more localized effects than hydrophilic opioids (morphine)

    • Side effects of neuraxial opioids include respiratory depression, nausea, vomiting, pruritus, and urinary retention

    • Opioid antagonists can be used cautiously to reverse adverse effects, but may also reverse analgesia

    • Total opioid dose required for neuraxial administration is significantly lower than systemic administration

    • Intrathecal administration requires less opioid for equivalent analgesia than epidural administration

    • Neuraxial opioids can be an excellent analgesic option for patients who cannot tolerate local anesthetics

    • Continuous spinal anesthesia is regaining popularity, with improved safety and lower incidence of hypotension compared to previous techniques

    Coagulation Considerations

    • Neuraxial procedures should occur at least 12 hours after prophylactic LMWH dosage and 24 hours after other LMWH regimens
    • Anti-Xa levels can be assessed for older patients or patients with impaired renal function
    • Heparin should be discontinued at least 6 hours before neuraxial procedures with normalization of PTT

    Choosing and Using Local Anesthetics

    • Local anesthetic selection is based on onset, duration, safety profile, and patient/procedure characteristics
    • Bupivacaine is a suitable alternative to lidocaine for ambulatory procedures as it is less associated with TNS
    • Bupivacaine and ropivacaine offer sensory:motor dissociation for less motor block with a given level of sensory block
    • Epidural analgesia can be achieved by adjusting the concentration, type, and infusion rate of local anesthetics to minimize motor blockade
    • Segmental block refers to the localized effect of epidural anesthesia, with the most intense block near the injection site
    • Epidural catheter placement should be as close to the surgical site as possible
    • Local anesthetic spread is influenced by volume, age, pregnancy, obesity, height, and spinal anatomy
    • Continuous spinal anesthesia is a safe and effective technique that allows for titration of local anesthetics to effect

    Neuraxial Anesthesia Use Beyond Surgery

    • Neuraxial analgesia can be used for pain management in conditions like rib fractures, vascular access procedures, and high-risk procedures
    • Spinal anesthesia eliminates dysautonomia risk in patients with high spinal cord injury
    • Enhanced recovery after surgery (ERAS) protocols emphasize multimodal analgesia and minimizing systemic opioid use

    Postoperative Assessment

    • Postoperative assessment includes evaluating patient satisfaction, regression of sensory and motor block, back pain, headache, pain relief adequacy, and presence of side effects
    • Thorough neurological examination is important to localize any residual blockade or neurological deficits
    • Epidural blood patch (EBP) is the gold standard treatment for PDPH
    • NSAIDs are the first-line treatment for TNS

    Key Points

    • Spinal anesthesia can increase sensitivity to sedative medications
    • Patients requiring spinal anesthesia require close monitoring, with fluid resuscitation and vasopressor support as needed
    • Postdural puncture patients should be monitored for PDPH
    • TNS is associated with lidocaine spinal anesthetics and is treated conservatively with NSAIDs

    Brachial Plexus Blocks for Upper Extremity Surgery

    • Supraclavicular Block
      • Provides anesthesia from below the deltoid to the fingers
      • Can be effective for shoulder surgery depending on technique
      • 50% chance of phrenic nerve blockade
      • Increased risk of pneumothorax
      • Ultrasound guidance advised
    • Infraclavicular Block
      • Provides anesthesia from the mid-humerus to the fingers
      • Can be more technically challenging due to steep approach required
    • Axillary Block
      • Provides anesthesia from the mid-humerus to the fingers
      • Frequently spares the musculocutaneous nerve, requiring separate blocking
      • Requires patient to abduct arm

    Brachial Plexus Block Technique

    • Supraclavicular Block:
      • Performed in the semi-sitting position, with the head turned to the opposite side.
      • Arm is reached to the ipsilateral lower extremity and externally rotated to depress the clavicle.
      • Needle is advanced from lateral to medial, surrounding the divisions of the brachial plexus, lateral to the subclavian artery.
      • Caution to avoid traversing arteries, as anatomy varies extensively in the supraclavicular region.
    • Infraclavicular Block:
      • Block is performed supine with arm positioned either at the patient's side or above the head to elevate the clavicle.
      • Probe is oriented cephalad to caudad at the level of the coracoid process.
      • Needle is advanced until it is at the 6 o'clock position of the axillary artery.
      • One injection provides coverage of all three cords of the brachial plexus.
      • U-shaped spread is essential on both sides of the artery to avoid sparing of the medial or lateral cords.
    • Axillary Block:
      • Performed with the patient's arm abducted to approximately 90 degrees.
      • Transducer is placed along the medial aspect of the arm in the axilla.
      • Needle is traversed from cephalad to caudad to the 6 o'clock position of the axillary artery.
      • Multiple injections are often required for circumferential anesthetic spread to the median, ulnar, and radial nerves.
      • Separate needle insertion point may be needed to anesthetize the musculocutaneous nerve.

    Brachial Plexus Block Risks

    • Supraclavicular Block:
      • Increased risk of pneumothorax compared to infraclavicular and axillary approaches.
      • Risk is minimized with proper needle tip visualization using ultrasound guidance.
      • Caution needed to avoid intravascular injection into the subclavian artery or surrounding vessels.
    • Infraclavicular Block:
      • Increased risk of intravascular injection.
      • Deep block with steep angle of insertion makes needle visualization difficult.
      • Aspiration before each injection is important to ensure the needle tip is not in the axillary artery or vein.
    • Axillary Block:
      • Considered the least risky compared to other brachial plexus blocks.
      • The superficial location of the axillary artery allows for manual compression in case of arterial puncture, preventing hematoma formation.

    Lower Extremity Nerve Blocks

    • Lumbar Plexus:
      • Gives rise to the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.
      • Common blocks include lumbar plexus, femoral, and saphenous nerve blocks.
    • Sacral Plexus:
      • Gives rise to the sciatic nerve, superior and inferior gluteal nerves, pudendal nerve, and posterior cutaneous nerve of the thigh.
      • Common blocks include the transgluteal sciatic, subgluteal sciatic, popliteal sciatic, and ankle blocks.

    Lower Extremity Block Technique

    • Lumbar Plexus Block:
      • Considered a deep block.
      • Needle insertion point is 4 to 5 cm lateral to the L4-L5 interspace, as approximated by the top of the iliac crest.
      • Performed with nerve stimulator guidance to elicit quadriceps muscle contraction.
      • Lumbar plexus is located in the body of the psoas major muscle, typically 2 cm deep to the transverse process of the lumbar spine.
      • Needle insertion depth is often between 6 and 8 cm depending on body habitus.
    • Femoral Nerve Block:
      • Common block for anterolateral thigh and medial skin below the knee anesthesia.
      • Nerve is visualized 1 cm lateral to the femoral artery, deep to the fascia iliaca, and superficial to the iliopsoas muscle using ultrasound guidance.
    • Saphenous Nerve Block:
      • Largest cutaneous branch of the femoral nerve.
      • Blocked deep to the sartorius muscle, inside the adductor canal, next to the superficial femoral artery.
    • Sciatic Nerve Block:
      • Found deep to the gluteus maximus, in between the ischial tuberosity and greater trochanter of the femur.
      • Subgluteal approach is often less technically challenging and easier to visualize by ultrasound.
    • Popliteal Sciatic Block:
      • Sciatic nerve has a variable branchpoint into the common peroneal and tibial nerves.
      • Nerve is found posterior to the femur and posterolateral to the popliteal artery using ultrasound guidance.
      • Muscle borders include the semitendinosus and semimembranosus medially and the biceps femoris laterally.

    Lower Extremity Block Risks

    • Nerve Injury:
      • Rare and not completely understood phenomenon.
      • Preexisting neuropathy increases the risk of nerve damage due to intraneural injection, ischemia, or anesthetic toxicity.
    • Intravascular Injection:
      • Risk is higher with deep blocks, like the lumbar plexus block.
      • Can lead to complications such as aortic perforation, retroperitoneal hematoma, intrathecal injection, and even bowel perforation.

    Plane Blocks vs. Peripheral Nerve Blocks

    • Plane Block:
      • Involves anatomical areas where no distinct nerve needs to be identified.
      • Local anesthetics are infiltrated into fascial planes where various nerves traverse.
      • Offers analgesia to the abdomen, chest, and trunk.
      • Requires larger volumes of local anesthetic compared to peripheral nerve blocks.
      • Reduced risk of needle-induced nerve damage due to smaller or absent nerves at the injection site.
    • Peripheral Nerve Block:
      • Involves direct injection of anesthetic around a specific nerve.

    Truncal Nerve Blocks for Thoracic, Breast, and Abdominal Surgery

    • Thoracic Paravertebral Block:
      • Delivers local anesthetic into the paravertebral space, where thoracic spinal nerves and the sympathetic trunk reside.
      • Provides unilateral anesthesia to 3-7 dermatomes of the chest wall or abdomen surrounding the insertion point, making it suitable for smaller surgeries.
    • Transversus Abdominis Plane (TAP) Block:
      • Indicated for lower abdominal surgeries.
      • Local anesthetic is deposited into the fascial plane between the internal oblique and transversus abdominis muscles.
      • Anterior divisions of T10-L1, iliohypogastric, and ilioinguinal nerves lie in this plane.
      • Provides unilateral anesthesia to the lower anterior abdominal wall, including the groin.
      • Upper abdomen can be blocked using the subcostal TAP approach.

    Truncal Nerve Blocks: An Overview

    • Erector Spinae Block:
      • Plane of injection is between the transverse process of the vertebra and the erector spinae muscles.
      • Blocks thoracic/lumbar spinal nerves.
      • Indications include breast, chest, upper, and lower abdominal surgery depending on injection point.
    • PECS I Block:
      • Plane of injection is between pectoralis major and pectoralis minor.
      • Blocks lateral and medial pectoral nerves, providing partial coverage for breast surgery.
    • PECS II Block:
      • Plane of injection is between pectoralis minor and serratus anterior.
      • Blocks thoracic intercostal nerves and the long thoracic nerve.
      • Indications include breast surgery, including axillary dissection.
    • Serratus Anterior Block:
      • Plane of injection is deep to the serratus anterior muscle.
      • Blocks thoracic intercostal nerves, thoracodorsal, and long thoracic nerves.
      • Indications include procedures of the hemi-thorax, including breast and thoracic surgery.
    • Quadratus Lumborum Block:
      • Plane of injection is at the anterolateral border of the quadratus lumborum muscle.
      • Blocks thoracic/lumbar spinal nerves.
      • Indications include upper or lower abdominal surgeries.

    Truncal Nerve Block Risks

    • Paravertebral Block:
      • Increased risk of pleural puncture and injection, resulting in pneumothorax, due to proximity to the pleura.
      • Possible epidural spread, leading to unintended contralateral block effects and hemodynamic changes.
      • Frequent occurrence of vagal reactions.
    • TAP Block:
      • Increasingly safe with the use of ultrasound.
      • Rare but possible complications include intraperitoneal injection and potential injury to abdominal viscera.

    Truncal Nerve Block Advantages and Disadvantages

    • Paravertebral Block:
      • Advantages: Versatile for various truncal procedures, provides dense analgesia often effective for surgical anesthesia.
      • Disadvantages: Higher risk compared to newer truncal blocks due to its location.
    • PECS & Serratus Anterior Blocks:
      • Advantages: Easier to perform with equivalent analgesia and lower risk compared to paravertebral block.
      • Advantages: PECS blocks block the pectoral nerves, which are spared by other techniques.
      • Disadvantages: Limited to breast surgery.
    • TAP & Quadratus Lumborum Blocks:
      • Advantages: Easier to perform and lower risk compared to paravertebral block.
      • Advantages: Quadratus lumborum block covers more dermatomes with fewer injections.
      • Disadvantages: Quadratus lumborum cannot be performed supine and is more challenging compared to the TAP block.
    • Erector Spinae Block:
      • Advantages: Can be used for the same indications as the paravertebral block with lower risk of direct injury or nerve-threatening hematoma.
      • Disadvantages: Less effective analgesia and benefits not well-documented.

    Key Points: Peripheral Nerve and Trunk Blocks

    • Nerve blocks can provide anesthesia or analgesia, allowing patients to avoid general anesthesia and periprocedural pain medication.
    • Upper extremity nerve blocks mainly involve blocking the brachial plexus at different anatomical locations.
    • Lower extremity nerves are derived from the lumbar and sacral plexuses.
    • Increased use of ultrasound has led to various novel truncal blocks.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge on the intricacies of peripheral nerve block techniques, including contraindications, advantages, and disadvantages. This quiz covers essential aspects such as the benefits of regional anesthesia, tissue perfusion, and ultrasound-guided approaches. Evaluate your understanding of key concepts related to anesthesia practices.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser