Central Neuraxial Anesthesia Study Guide PDF

**Central Neuraxial Anesthesia** Spinal/Epidural - Spinal and epidural are both known as central neuraxial block - Both commonly used techniques - Both can be used as adjuncts to general anesthesia - Both can be used as an alternative to GA - Both used in obstetrics Spinal Anesthesi...

**Central Neuraxial Anesthesia** Spinal/Epidural - Spinal and epidural are both known as central neuraxial block - Both commonly used techniques - Both can be used as adjuncts to general anesthesia - Both can be used as an alternative to GA - Both used in obstetrics Spinal Anesthesia - Injection of local anesthetic into the CSF - CSF is found within the subarachnoid space - The layers penetrated by the spinal needle are: - Skin - Subcutaneous tissue - Supraspinus ligament - Intraspinus ligament - Ligamentum Flavum - (Epidural space) - - Advantages - Less time - Less discomfort - Less local anesthetic - More intense sensory block - More motor block - Placement confirmed by the appearance of CSF Epidural Advantages - Reduced risk for headache - Lower risk for hypotension - Able to produce a segmental sensory block - Better control over the intensity of sensory block - Ability to produce motor block achieved by adjustment of the local anesthetic concentration - Placement of a catheter for epidural anesthesia allows titration of the block for the duration of surgery - Allows for postoperative infusion Vertebral Canal A close-up of a spine Description automatically generated - **L3** and **C5** are the most significant points of **LORDOSIS** - **T7** and the **Sacrum** are the most significant points of **KYPHOSIS** - *Consider these points with how baricity will effect the spread of LA when the patient is supine* - A HYPObaric solution will spread to L3 when the patient is supine - A HYPERbaric solution will spread to T7 and the sacrum when the patient is supine - **Sensory Block** will occur \~ 2 levels **ABOVE** the site of injection - **Motor Block** will occur \~ 2 levels **BELOW** the site of injection  Anatomy of the Spine - Vertebrae - 7 C - 12 T - 5 L - 5 S - 4 Coccygeal - Must know bony anatomy of spine to determine best approach and how to reangle the needle if you hit bone - The opening between the unfused lamina of the fourth and fifth sacral vertebrae is called the sacral hiatus - The sacral hiatus is absent in nearly 8% of adults - The **sacrococcygeal ligament** provides access to the sacral canal and epidural space. Performance of caudal anesthesia is performed via the caudal canal (usually for Peds cases)  Landmarks - A line drawn between the **iliac crests** traverses the body of the **L4** - **C7 spinous** process can be noted as a **bony prominence at the inferior neck**. - **T7-T8** interspace is identified by a **line drawn between the of the scapulae** and is used to estimate needle placement for a thoracic epidural - The **terminal portion of the twelfth rib** intersects the **L2** vertebral body - The **posterior iliac spines** indicate the level of the **S2** vertebral body - *The elbows with arms at side will give and approximate height of the iliac crests (L4)* A diagram of a baby\'s body Description automatically generated Meninges - Dura mater - Subdural space - Arachnoid membrane -- - Pharmacologic barrier preventing movement of drug from the epidural to the subarachnoid space - Pia  Anatomy of the Epidural Space - Surrounds the Dural Sac - Anteriorly: Posterior Longitudinal Ligament - Posteriorly: Ligamentum Flavum - Laterally: Pedicles and Intervertebral Foramina - *Works around the "dural cuff" on the spinal nerves coming out of the spinal cord.* Positioning for Spinal / Epidural - Lateral position is more comfortable and more suitable for the ill or frail - Sitting is most commonly used - Promotes flexion - Allows for better recognition of the midline - May be of increased importance in an obese patient - Better for OB and obese - Fractured hip = Lateral - Knee -\> lateral with operative side down (spinal) Selection of Interspace - The specific anatomy of the patient\'s spine and the likelihood that a needle can be successfully passed into the subarachnoid space - Interspace selected for spinal anesthesia has considerable impact on the distribution of anesthetic within the subarachnoid space (higher failure at L4-5) - The **spinal cord end** in an **adult** usually lies between the **L1 and L2** vertebrae - The end of the cord is called? **Conus Medullarris** - What is below the cord? **Cauda Equina** Approach - Midline - Paramedian technique - **10-15 degrees** off midline - Anesthetizes the Emerging Nerve Roots of the Spinal Cord - Epidural Injection of Anesthetic Produces a Regional Dermatomal "band" of Anesthesia Spreading Cephalad and Caudad from the Site of Injection - Level of Anesthesia Depends on: - Volume of the Drug - Level of Injection - Epidural Use - Surgeries involving the abdomen - Surgery involving the chest- Supplemental or post op pain control - Lower extremities - Suboptimal for procedures involving the lower sacral roots - Frequently used as a supplement to general anesthesia - Epidural anesthesia is also used for the control of [labor pain] - **Lumbar Epidural**: Lower Extremity, Pelvic, and Lower Abdominal Procedures - **Thoracic Epidural**: Upper Abdomen and Thoracic Procedures - **Caudal Injection**: More Commonly Used for Pediatric Patients (Genitourinary and Lower Abdominal Procedures) - *More volume = higher + lower LA spread* - Epidural Advantages - Superior Pain Relief- compared to IV opioids - Less Systemic Side Effects - Lower Incidence of DVT and Pulmonary Emboli - Earlier Ambulation - Decreased Blood Loss Intraoperatively during Orthopedic, Urologic, Gynecologic and Obstetric Procedures - Faster Recovery of Bowel Function- compared to IV opioids - Better PFT (pulmonary function tests) - Suppression of Neuroendocrine Stress Response - *Less risk of PDPH when done correctly* - *Sensory nerves more sensitive to LA than Motor Nerves* - *Use a stronger concentration for a motor block in cases such as C-section* - Contraindications - Absolute - Patient Refusal - \*Coagulopathy\* - Increased ICP - Skin Infection - Relative - Uncooperative Patient - Pre-existing Neurologic Disorder - Anatomical Abnormalities - Coagulopathy - **Ticlopidine** longest wait time \~**10 days** - Plavix (clopidogrel), Ticagrelor (Brilinta) 5-7 days - **ASA** don't need to stop if sole blood thinner and coagulation status appears normal - Unfractionated **Heparin SQ 4-12 hrs** - **IV heparin therapeutic dose 24 hrs** - **Enoxaparin 12 hours before and after** - **Herbal supplements** - Ginkgo - Ginger - Ginseng - **Severe aortic / mitral stenosis** BP dependent on preload - **Hypertrophic Cardiomyopathy** - Tattoo generally safe unless it is "dirty" tattoo - Sepsis potential for encephalitis - MS Generally considered safe, may exacerbate symptoms - Severe hypovolemia - Previous "Coflex" procedure Coflex Local Anesthetics (Epidural) - **Bicarb** speeds up **onset** of block - **Epi** prolongs **duration** of block Epidural Test Dose A white background with black text Description automatically generated Opioids in the Epidural Space - Morphine most **Hydrophilic** - Fentanyl and Sufentanil most **Lipophilic** **Characteristic** **Hydrophilic Opioids (More Water Soluble)** **Lipophilic Opioids (More Fat Soluble)** --------------------------------------- ---------------------------------------------------------------------------- -------------------------------------------------------- **How Long Does it Stay in the CSF?** Stays in CSF for longer time period Stays in CSF for shorter time period **CSF Spread** Extensive, Wide band of analgesia, More rostral spread (towards the brain) Minimal, Narrow band of analgesia, Less rostral spread **Site of Action** Rexed laminae 2 & 3 Rexed laminae 2 & 3, Systemic **Onset** Delayed (30 -- 60 min) Fast (5 -- 10 min) **Duration** Longer (6 -- 24 hours) Shorter (2 -- 4 hours) **Systemic Absorption** Less (This is why it stays in the CSF longer) More **Respiratory Depression** Early (\< 6 hours), Late (\> 6 hours) Early only **Nausea & Vomiting** Higher incidence Lower incidence **Pruritus** Higher incidence Lower incidence Complications of Epidurals - Failure of Block (Patchy or Unilateral Block) - Injury to Nerve - Infection - Epidural Hematoma or Abscess - Dural Puncture (Total Spinal or PDPH) - Post dural puncture headache - Side Effects of Drugs in the Epidural Space - Hypotension secondary to sympathetic blockade - Intravascular Injection (Local Anesthetic Toxicity) - Respiratory Depression - Sedation - Bladder Distention - Difficulty in Ambulation Spinal Anesthesia - Spinal Anesthesia is Induced by Injecting Small Amount of Local Anesthetic (most commonly Bupivacaine) in the CSF - Results in Rapid Onset of Block - More Rapid Onset and Requiring less Medicine Compared to Epidural Analgesia - CSE- combined spinal epidural - Used in Labor - Preservative Free Morphine (Duramorph) Provides Pain Relief for Abdominal, Pelvic, or Lower Extremity Surgeries - Complications Similar to Epidural Technique Except for Higher Risk of PDPH - Risks - Nerve damage - Infection - Bleeding - PDPH - \*no common serious complications Level and Duration - Baricity of solution - Contour of the spinal canal - Position of the patient during and immediately following placement of drug - Presence or absence of vasoconstrictor - Progression, regression is predictable - Hypobaric- Baricity less than CSF; floats up - Hyperbaric- Baricity more than CSF; sinks down - Isobaric- Same Baricity as CSF ; stays around area of injection - **Hyperbaric most used We don't want LA floating up to the brain** - **Hypobaric may be used in specific circumstances ex: jackknife position for hemorrhoid surgery** Short Acting Spinal LAs - Procaine short acting ester - More frequent failure rate - More nausea - Slower time to recovery - Hyperbaric 50-200mg in 10% concentration - Chloroprocaine ultra short acting ester **pseudocholinesterase metabolism** - Minimal fetal side effects - Neurologic injury with the preservative once used in older preparations of the drug - Lidocaine hydrophilic, poorly protein bound amide - 50-100mg for 1.5 hour procedures in 5% concentration; (hyperbaric with dextrose 7.5%) - TNS and permanent nerve injury association - Prilocaine amide similar to lidocaine - 40-60mg of 2% hyperbaric solution to T10 for 100-130 minutes - In large doses (\>600mg) can cause methemoglobinemia - Mepivacaine amide - TNS similar incidence as lidocaine - 30-80mg in 1.5% has slightly longer duration than lidocaine Long-Acting Spinal LAs - Tetracaine ester, slow rate of metabolism - mixing 1% solution with 10% dextrose produces a 0.5% hyperbaric preparation in doses of 5-15 mg - when mixed with vasoconstrictor, can last up to 5 hours - addition of phenylephrine associated with TNS - Bupivacaine highly protein-bound amide with slow onset because of high pKa - lasts 2.5-3 hours 10-20 mg - 0.25%, 0.5%, 0.75% isobaric solutions - 0.5% and 0.75% hyperbaric solutions (usually in 80 mg/mL glucose=8.25%) - rarely associated with TNS - 4-5 mg can be used for short procedures - Levobupivacaine pure S(-) enantiomer of racemic bupivacaine - less potent, less cardiotoxic, no difference in efficacy for SAB - Ropivacaine highly protein-bound amide similar to bupivacaine, high pKa of 8.1= slow onset, long duration of action - less potent (0.6), less cardiotoxic, greater motor-sensory block differentiation=less motor block, earlier recovery when compared to bupivacaine - Less risk for LAST Needles **Tip Type** **Needle** **Pros** **Cons** --------------------- --------------------------------------------- -------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------- **Cutting Tip** Quincke, Pitkin Requires less force Higher risk of PDPH, Less tactile feel, Needle more easily deflected, More likely to injure cauda equina **Non-Cutting Tip** Pencil point tip: Sprotte, Whitacre, Pencan Lower risk of PDPH, More tactile feel, Needle less likely to deflect, Less likely to injure the cauda equina Requires more force Rounded bevel tip: Greene Requires more force Several different types of pencils Description automatically generated - Most epidural needles are 9cm - Optimal catheter length is 3-5cm in the epidural space - Total catheter inside the pt (skin +epidural space) shouldn't exceed 10cm - **If you need to retract the catheter, pull both the needle and the catheter back at the same time so the catheter doesn't shear off inside of the patient \#Lawsuit** Caudal Anesthesia - Single Injection or Continuous Infusion through a Catheter - Excellent Intraoperative and Postoperative Pain Control - Easier to Perform in Children - Analgesia that Last About 12 hrs if Bupivacaine Used - Performed Following Induction of General Anesthesia - Surgeries in Sacral Segments, (Circumcision and other Urologic Surgeries, Rectal Dilation) - Combined with Light General Anesthesia Provides Adequate Intraoperative Analgesia - Complications - Infection - Dural Puncture and Spinal Anesthesia - Intravascular Injection of Local Anesthetics Complications Post-Dural Puncture Headache (PDPH) - Fronto-occipital HA, worse when upright vs. supine - N/V - Photophobia - Diplopia - Tinnitus **Factors** **Higher Risk of PDPH** **Lower Risk of PDPH** **No Effect on Risk of PDPH** -------------------------- -------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------- **Patient Factors** Younger age, Female, Pregnancy Older age, Male, Non-pregnant Early ambulation **Practitioner Factors** Cutting tip needle, Larger diameter needle, Using air for LOR with epidural, Needle perpendicular to long-axis of the neuraxis Non-cutting tip needle, Smaller diameter needle, Using fluid for LOR with epidural, Needle parallel to long-axis of the neuraxis, Continuous spinal catheter (if placed after wet tap) Continuous spinal catheter (if placed after spinal block) Treatment - Epidural Blood Patch (**Definitive Treatment)** - 10-20 mL of the patient's venous blood injected into the epidural space - Compresses the epidural and SA space to increase CSF pressure - Acts as a plug to prevent further leaks - Side Effects: **Back ache and Radicular Pain** - Bed Rest - NSAIDs - Caffeine - Sphenopalatine Ganglion Block - Cotton-tipped applicator soaked in 1-2% lido or 0.5% bupiv - Place the patient in sniffing position - Put the applicator to the back of the nasopharynx and leave for 5-10 min to anesthetize the sphenopalatine ganglion  Post-Spinal Bacterial Meningitis - Caused by failure of aseptic technique / sepsis - Must use sterile technique for procedures - Iodine - Alcohol - CHG - Must allow to dry because the chemical is neurotoxic Spinal Induced Hypotension (SIH) - Increased Risk - High block ( \>T5) - Age \>40 years - Pre-block SBP \