Pathophysiology of Pain: Anatomy of Pain and Somatosensory System

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Questions and Answers

Which type of neurons transmit pain signals from the periphery to the spinal cord?

A-delta and C fibers

Motor neurons

First-order neurons (correct)

Third-order neurons

What is the primary function of the periaqueductal gray matter?

Inhibition of pain transmission (correct)

Transmission of pain signals to the brain

Processing of sensory information

Regulation of motor function

What is the term for the perception of an ordinarily non-noxious stimulus as pain?

Allodynia (correct)

Hyperalgesia

Dysesthesia

Hypoalgesia

What is the term for the absence of all sensation?

Anesthesia Signup and view all the answers

Which part of the brain receives fibers from third-order neurons?

Postcentral gyrus of the parietal cortex Signup and view all the answers

What is the term for pain in the distribution of a nerve or a group of nerves?

Neuralgia Signup and view all the answers

What is the term for an abnormal sensation perceived without an apparent stimulus?

Paresthesia Signup and view all the answers

What is the term for the presence of hyperesthesia, allodynia, and hyperalgesia?

Hyperapthia Signup and view all the answers

What is the primary function of neutrophils in response to invading microbes?

To engulf and kill invading microbes and release more inflammatory cytokines Signup and view all the answers

What is the primary cause of pain in patients who experience psychogenic pain?

A psychological problem or disturbance Signup and view all the answers

What is somatization disorder characterized by?

Physical symptoms of a medical condition that cannot be explained Signup and view all the answers

What percentage of children and adolescents are affected by chronic pain worldwide?

20-35% Signup and view all the answers

What type of pain is often made worse by touch, movement, emotions, and temperature changes?

Central pain Signup and view all the answers

What is the primary characteristic of malingering?

Intentional production of physical or psychological symptoms Signup and view all the answers

What is a predictor of the development of chronic postsurgical pain in children?

Pain unpleasantness Signup and view all the answers

What is a characteristic of superficial somatic pain?

Sharp, pricking, throbbing, burning Signup and view all the answers

What is the mechanism of central pain?

Lesions in the brain or nervous system Signup and view all the answers

What is the primary difference between inflammatory pain and central pain?

The location of the lesion or injury Signup and view all the answers

What is a characteristic of visceral nociceptive pain?

Dull and poorly localized Signup and view all the answers

What is a subtype of visceral nociceptive pain?

Localized parietal pain Signup and view all the answers

What is the primary characteristic of chronic pain?

Pain secondary to changes in the nervous system Signup and view all the answers

What is a common symptom associated with visceral pain?

Nausea and vomiting Signup and view all the answers

What is a predictor of the persistence of chronic postsurgical pain in children?

Anxiety sensitivity Signup and view all the answers

What type of pain is characterized by a defined time period?

Ongoing time-limited pain Signup and view all the answers

Which component of pain refers to the neural response to traumatic or noxious stimuli?

Nociception Signup and view all the answers

What is true about the relationship between nociception and pain?

Not all pain results from nociception Signup and view all the answers

Where does the process of perceiving pain begin?

The dorsal horn of the spinal cord Signup and view all the answers

What is suffering, in the context of pain?

A negative affective response generated in the brain Signup and view all the answers

What is the primary focus of most commonly employed assessment strategies for pain?

Pain behaviors Signup and view all the answers

What can trigger pain, according to the perception of pain component?

The anticipation of potential pain Signup and view all the answers

What is the relationship between pain and suffering?

Suffering is a distinct component of the pain experience Signup and view all the answers

What is a common manifestation of pain in patients who are non-verbal or unable to describe their pain?

Vocalizations of distress Signup and view all the answers

What is a physiologic effect of pain on the cardiovascular system?

Hypertension Signup and view all the answers

What is a consequence of chronic pain on the immune system?

Increased risk of infection Signup and view all the answers

What is a long-term impact of chronic pain on the nervous system?

Plasticity leading to sensitization Signup and view all the answers

What is a gastrointestinal effect of pain?

Hypersecretion of gastric acid Signup and view all the answers

What is a benefit of multimodal anesthesia?

Pain relief through intervening at multiple points Signup and view all the answers

What is a hematologic effect of pain?

Increased platelet adhesiveness Signup and view all the answers

What is a respiratory effect of pain?

Increased total body O2 consumption Signup and view all the answers

What is an advantage of using ultrasound-guided regional anesthesia techniques?

Allows for improved visualization of nerve location and surrounding anatomic structures Signup and view all the answers

What is a limitation of ultrasound-guided regional anesthesia techniques?

Adds an additional layer of complexity Signup and view all the answers

What is a benefit of using ultrasound-guided regional anesthesia techniques?

Improves the block quality and onset time Signup and view all the answers

What is a characteristic of traditional nerve stimulation techniques?

Relies heavily on anatomic landmarks Signup and view all the answers

What is an advantage of using ultrasound-guided regional anesthesia techniques over traditional techniques?

Improves the ability to differentiate perineural injection from unintentional epineural injection Signup and view all the answers

What is a potential drawback of using ultrasound-guided regional anesthesia techniques?

Adds an additional layer of complexity Signup and view all the answers

What is a benefit of using ultrasound-guided regional anesthesia techniques in terms of needle advancement?

Provides real-time imaging of needle advancement Signup and view all the answers

What is an advantage of using ultrasound-guided regional anesthesia techniques in terms of learning curve?

Accelerates the learning curve for regional anesthesia Signup and view all the answers

What is the recommended length of a needle for an interscalene brachial plexus block?

25 mm (1 in) to 50 mm (2 in) Signup and view all the answers

What is the term for the plane that divides the body into left and right halves?

Sagittal plane Signup and view all the answers

What is a benefit of continuous infusion catheters in pain management?

Prolonged analgesia Signup and view all the answers

What is the primary purpose of in-plane needle guidance?

To visualize the needle tip Signup and view all the answers

What is the recommended length of a needle for a lumbar plexus block?

50 mm (2 in) to 100 mm (4 in) Signup and view all the answers

What is the benefit of practice in ultrasound-guided regional anesthesia?

All of the above Signup and view all the answers

What is the recommended length of a needle for a sciatic block with an anterior approach?

100 mm (4 in) to 150 mm (6 in) Signup and view all the answers

What is a benefit of single-injection nerve blocks?

Faster onset of analgesia Signup and view all the answers

What is the term for the view created when the structures are at a right angle to the probe?

Cross-sectional view Signup and view all the answers

What is the purpose of out-of-plane needle guidance?

To direct the needle at the target perpendicularly Signup and view all the answers

What is the recommended length of a needle for a popliteal block with a posterior approach?

25 mm (1 in) to 50 mm (2 in) Signup and view all the answers

What is a benefit of continuous infusion catheters in rehabilitation?

Improved ability to participate in rehabilitation Signup and view all the answers

What is the term for the plane that divides the body into front and back halves?

Frontal plane Signup and view all the answers

What is the recommended length of a needle for a cervical plexus block?

25 mm (1 in) to 50 mm (2 in) Signup and view all the answers

What is the benefit of the 3 probe maneuvers (A, R, T) in ultrasound-guided regional anesthesia?

All of the above Signup and view all the answers

What is the primary focus of clinical application in ultrasound-guided regional anesthesia?

Matching the appropriate mode of pain control with the surgery Signup and view all the answers

What is a potential cause of nerve injury following a peripheral nerve block?

A hematoma compressing a nerve Signup and view all the answers

What is the primary focus of the anesthesia team in the preoperative management phase?

Patient selection and education Signup and view all the answers

What does the acronym SCANNING stand for in the context of anesthesia?

Supplies, Comfortable positioning, Ambiance, Nominate a transducer, Name and procedure, Infection control, Note lateral/medial side on screen, Gain and depth adjustments Signup and view all the answers

What is the primary reason for following up with patients after a peripheral nerve block?

To monitor for potential complications Signup and view all the answers

What is a key component of the anesthesia team's technique in regional anesthesia?

Proficiency of the clinician Signup and view all the answers

What is the primary goal of preoperative management in regional anesthesia?

To prepare the patient for the procedure Signup and view all the answers

What is a critical aspect of postoperative management in regional anesthesia?

Monitoring for potential complications Signup and view all the answers

What is the primary responsibility of the anesthesia team in regional anesthesia?

To manage the patient's pain and comfort during and after the procedure Signup and view all the answers

What is a characteristic of cryoneurolysis?

It is similar in technique to ultrasound-guided peripheral nerve blockade. Signup and view all the answers

What is the primary advantage of cryoneurolysis over other treatments?

It is not specified in the content. Signup and view all the answers

What is the purpose of cryoneurolysis?

To treat acute pain. Signup and view all the answers

What is the name of the nerve that was treated with percutaneous cryoneurolysis in a pilot study?

Lateral femoral cutaneous nerve. Signup and view all the answers

Where is cryoneurolysis typically performed?

In the OR, IR, or procedure room. Signup and view all the answers

What is the level of sedation required for cryoneurolysis?

Sedation not necessarily required. Signup and view all the answers

What is the name of the device used for cryoneurolysis?

Novel cryoneurolysis device. Signup and view all the answers

Who wrote a narrative review on cryoneurolysis and percutaneous peripheral nerve stimulation?

Finneran IV, John J. Signup and view all the answers

What is the primary goal of incorporating UGRA into clinical practice?

To reduce the use of opioids in post-operative pain management Signup and view all the answers

According to the ASA Multimodal Guidelines, what should be considered after thoughtful consideration of the risks and benefits for the individual patient?

Therapeutic options such as central regional opioids, systemic opioid PCA, and peripheral regional techniques Signup and view all the answers

What is the benefit of using ultrasound-guided regional anesthesia techniques in terms of needle advancement?

Real-time visualization of needle placement Signup and view all the answers

What is the primary focus of the clinical goals outlined in the course objectives?

Treating pain aggressively Signup and view all the answers

What is the advantage of using ultrasound-guided regional anesthesia techniques over traditional techniques?

Real-time visualization of needle placement Signup and view all the answers

What is the primary characteristic of the course objectives outlined in the content?

Focusing on the essential principles of ultrasound in regional anesthesia Signup and view all the answers

What is the recommended approach to pain management according to the ASA Multimodal Guidelines?

Multimodal pain management Signup and view all the answers

What is the benefit of integrating non-opioid related therapies into clinical practice?

Reduced risk of opioid-related adverse effects Signup and view all the answers

What is the recommended needle length for a cervical plexus block?

50 mm (2 in) Signup and view all the answers

What is a benefit of continuous infusion catheters in pain management?

Prolonged analgesia Signup and view all the answers

What is the primary goal of multimodal pain management?

To provide around-the-clock analgesia Signup and view all the answers

What is the primary mechanism of regional anesthesia?

Blockade of nerve impulse conduction Signup and view all the answers

What is the recommended needle length for a thoracic paravertebral block?

90 mm (3.5-4 in) Signup and view all the answers

What is the recommended approach to pain management, according to the American Society of Anesthesiologists?

Multimodal therapy with COXIBs, NSAIDs, or acetaminophen Signup and view all the answers

What is the recommended needle length for a sciatic block using the anterior approach?

150 mm (6 in) Signup and view all the answers

What is the benefit of using regional anesthesia techniques in pain management?

Improved pain relief with fewer side effects Signup and view all the answers

What is a benefit of using ultrasound-guided regional anesthesia techniques?

Improved patient satisfaction Signup and view all the answers

What is a characteristic of regional anesthesia?

Temporary analgesia and loss of sensory function Signup and view all the answers

What is the recommended needle length for a lumbar paravertebral block?

100 mm (4 in) Signup and view all the answers

What is the recommended needle length for an axillary brachial plexus block?

50 mm (2 in) Signup and view all the answers

What is the recommended approach to pain management in patients at high risk of respiratory depression?

Multimodal therapy with non-opioid analgesics Signup and view all the answers

What is a benefit of using ultrasound-guided regional anesthesia techniques?

Higher success rates and fewer complications Signup and view all the answers

What is the recommended needle length for an infraclavicular brachial plexus block?

100 mm (4 in) Signup and view all the answers

What is the primary focus of the American Society of Anesthesiologists' guidelines for acute pain management?

Optimizing multimodal pain management Signup and view all the answers

What is crucial to follow after a patient receives regional anesthesia?

Monitoring until sensory and motor function return Signup and view all the answers

What could be the cause of a nerve injury following a peripheral nerve block?

Tight bandage or hematoma compressing a nerve Signup and view all the answers

What is essential for success in regional anesthesia?

All of the above Signup and view all the answers

What does the acronym SCANNING stand for in regional anesthesia?

Supplies, Comfortable positioning, Ambiance, Name and procedure, Nominate a transducer, Infection control, Note lateral/medial side on screen, Gain and depth adjustments Signup and view all the answers

Why is it essential to monitor patients who receive regional anesthesia?

To monitor until sensory and motor function return Signup and view all the answers

What is crucial in the management of patients receiving regional anesthesia?

All of the above Signup and view all the answers

What is essential for the anesthesia team when performing regional anesthesia?

All of the above Signup and view all the answers

Why is continuous monitoring essential after regional anesthesia?

To monitor until sensory and motor function return Signup and view all the answers

What is the primary benefit of programmed intermittent bolus over continuous epidural infusion for labor analgesia?

Fewer side effects with similar analgesic efficacy Signup and view all the answers

What is the primary advantage of liposomal bupivacaine infiltration over interscalene nerve block for total shoulder arthroplasty?

Similar pain relief with reduced risk of systemic toxicity Signup and view all the answers

What is the primary benefit of continuous interscalene block over single-injection interscalene block for major shoulder surgery?

Improved analgesic efficacy with reduced risk of nerve damage Signup and view all the answers

What is the primary advantage of programmed intermittent bolus over continuous infusion for peripheral nerve catheters?

Similar analgesic efficacy with reduced risk of systemic toxicity Signup and view all the answers

What is the primary benefit of local infiltration over interscalene nerve block for total shoulder arthroplasty?

Similar pain relief with reduced risk of systemic toxicity Signup and view all the answers

What is the primary advantage of continuous infusion over programmed intermittent bolus for peripheral nerve catheters?

Reduced risk of bleeding with similar analgesic efficacy Signup and view all the answers

What is the primary benefit of liposomal bupivacaine infiltration over continuous interscalene block for total shoulder arthroplasty?

Similar pain relief with reduced risk of systemic toxicity Signup and view all the answers

What is the primary advantage of programmed intermittent bolus over continuous infusion for labor analgesia?

Similar analgesic efficacy with reduced risk of systemic toxicity Signup and view all the answers

Study Notes

Anatomy of Pain

The somatosensory system is composed of peripheral nervous system, spinal cord, and brain.
Afferent neurons, A-delta and C fibers, transmit pain signals to the spinal cord.
The spinal cord has ascending and descending pathways that process pain information.
The somatosensory cortex, thalamus, and brain process pain information.

First-Order Neurons

First-order neurons transmit pain signals from the periphery to the spinal cord.

Ascending Pathways

Ascending pathways transmit pain signals from the spinal cord to the brain.
The periaqueductal gray matter is a key structure in the brain that initiates pain inhibition.

Third-Order Neurons

Third-order neurons transmit pain signals from the thalamus to the cortex.

Common Pain Terms

Allodynia: perception of non-noxious stimuli as pain.
Analgesia: absence of pain perception.
Anesthesia: absence of all sensation.
Anesthesia dolorosa: pain in an area that lacks sensation.
Dysesthesia: unpleasant or abnormal sensation with or without stimuli.
Hyperalgesia: increased response to noxious stimuli.
Hyperesthesia: increased response to mild stimuli.
Hyperapthia: presence of hyperesthesia, allodynia, and hyperalgesia.
Hypoalgesia: diminished response to noxious stimuli.
Hypoesthesia: reduced cutaneous sensation.
Neuralgia: pain in the distribution of a nerve or group of nerves.
Paresthesia: abnormal sensation perceived without stimuli.
Radiculopathy: functional abnormality of one or more nerve roots.

Classification of Pain

Etiology of pain: considering the anticipated tissue damage secondary to a procedure.
Duration of pain: chronic pain lasts more than 3 months.

Mechanism of Pain

Nociceptive pain: arises from tissue damage or inflammation.
Somatic nociceptive pain: superficial (sharp, pricking) or deep (dull, aching).
Visceral nociceptive pain: arises from internal organs, often poorly localized.
Neuropathic pain: arises from nerve damage or dysfunction.
Inflammatory pain: arises from inflammation and tissue damage.
Psychogenic pain: arises from psychological or emotional factors.
Central pain: arises from lesions in the brain or spinal cord.

Associated Emotional Disorders

Somatization disorder: physical symptoms cannot be explained, resulting in distress and impairment.
Conversion disorder: symptoms suggest a medical condition but are not explainable.
Hypochondriasis: prolonged fear of having a serious illness.
Malingering: intentional production of physical or psychological symptoms.
Substance-related disorders: habitual misuse of prescribed or illicit substances.

Physiologic Effects of Pain

Cardiovascular: hypertension, tachycardia, increased SVR.
Respiratory: increased O2 consumption, CO2 production, and minute ventilation.
GI and urinary: decreased motility, hypersecretion of gastric acid, nausea, vomiting, and constipation.
Hematologic: increased platelet adhesiveness, reduced fibrinolysis, and hypercoagulability.
Endocrine: increased catabolic hormones, decreased anabolic hormones, and development of negative nitrogen balance.
Immune: predisposes to infection.

Long Term Impact of Pain

Plasticity results in alterations in neuronal structure, interneuronal connections, and neurotransmitters.
Leads to sensitization and wind-up phenomenon.

Multimodal Anesthesia

Intervene at multiple points in the pain pathway to reduce pain transmission.

Motor Response

Disappears after injection of local anesthetic or saline
PNS does not prevent intravascular, intraneural, or pleural puncture

Ultrasound-Guided Regional Anesthesia (UGRA)

Decreases the incidence of block failure
Improves upon the false negative rate of nerve stimulation techniques
Allows for alternative approaches for nerve blockade
May accelerate the learning curve for regional anesthesia
Provides an additional layer of safety

Advantages of UGRA

Allows for visualization of nerve location and surrounding anatomic structures
Provides real-time imaging of needle advancement and local anesthetic injection
Reduces the number of needle insertions
Improves block quality, onset time, and success rate

Limitations of UGRA

Adds an additional layer of complexity
Needles may be slightly longer for certain blocks (e.g., cervical plexus block: 50 mm, interscalene brachial plexus block: 25-50 mm)

Needle Lengths for Different Blocks

Cervical plexus block: 50 mm
Interscalene brachial plexus block: 25-50 mm
Infraclavicular brachial plexus block: 100 mm
Axillary brachial plexus block: 25-50 mm
Thoracic paravertebral block: 90 mm
Lumbar paravertebral block: 100 mm
Lumbar plexus block: 100 mm
Sciatic block (posterior approach): 100 mm
Sciatic block (anterior approach): 150 mm
Femoral block: 50 mm
Popliteal block (posterior approach): 50 mm
Popliteal block (lateral approach): 100 mm

Single-Injection vs. Continuous Infusion

Catheter benefits: prolonged analgesia, improved ability to participate in rehabilitation, and improved patient satisfaction

Block Room

Short axis: cross-sectional view, structures at a right angle to the probe
Long axis: longitudinal view, structures and probe aligned
In-plane: visualization of entire needle, including tip
Out-of-plane: needle directed at the target in a perpendicular fashion, image may not represent the tip of the needle

Probe Orientation

Terminology: sagittal plane, transverse plane, frontal plane, oblique plane
Midsagittal plane and parasagittal plane are types of sagittal planes

Needle Guidance Principles

3 probe maneuvers: alignment, rotation, and tilt
2 needle maneuvers: advance or withdraw, change in angle of approach

Practice and Clinical Application

Evaluate patients for regional anesthesia
Match the appropriate mode of pain control with the surgery
Consider preoperative, intraoperative, or postoperative block
Follow patients until sensory and motor function return

Keys to Success

Anesthesia team
Preoperative management
Block selection
Proficiency of clinician
Knowledge of equipment
Local anesthetic solution

Acronym for Success: SCANNING

S: Supplies
C: Comfortable positioning
A: Ambiance
N: Name and procedure
N: Nominate a transducer
I: Infection control
N: Note lateral/medial side on screen
G: Gain and depth adjustments

Local Anesthetics

Sensory vs. motor

Cryoneurolysis

Performed in OR, IR, or procedure room
Sedation not necessarily required
Similar in technique to ultrasound-guided peripheral nerve blockade
Can be used to treat acute pain

Course Objectives

Describe essential principles of ultrasound in regional anesthesia
Demonstrate foundational knowledge requisite to be proficient in sonoanatomy
Apply imaging techniques and transducer maneuvers that improve ultrasound peripheral nerve image

The Challenge

Embracing a multimodal approach to pain management
Treating postsurgical pain aggressively
Reducing reliance on opioids to minimize undesired opioid-related adverse effects
Integrating non-opioid related therapies
Comparing systemic vs local interventions to treat pain at its source

Clinical Goals

Aggressive treatment of postsurgical pain
Reduced opioid use to minimize adverse effects
Integration of non-opioid related therapies
Comparing systemic vs local interventions for pain management

ASA Multimodal Guidelines

Utilize multimodal pain management whenever possible
Consider therapeutic options like central regional opioids, systemic opioid PCA, and peripheral regional techniques
Consider risks and benefits for individual patients
Recommend around-the-clock regimens of COXIBs, NSAIDs, or acetaminophen

Regional Anesthesia Defined

Regional anesthesia involves injecting local anesthetics around nerves or nerve groups
This results in temporary blockade of nerve impulse conduction, causing analgesia and loss of sensory and motor function

Multimodal Pain Management Rationale

Adopt a multimodal approach to pain management
Consider various therapeutic options for individual patients
Follow established guidelines for acute pain management

Regional Anesthesia Needles

Cervical plexus block: 50 mm (2 in)
Interscalene brachial plexus block: 25 mm (1 in) to 50 mm (2 in)
Infraclavicular brachial plexus block: 100 mm (4 in)
Axillary brachial plexus block: 25 mm (1 in) to 50 mm (2 in)
Thoracic paravertebral block: 90 mm (3.5-4 in)
Lumbar paravertebral block: 100 mm (4 in)
Sciatic block (posterior approach): 100 mm (4 in)
Sciatic block (anterior approach): 150 mm (6 in)
Femoral block: 50 mm (2 in)
Popliteal block (posterior approach): 50 mm (2 in)
Popliteal block (lateral approach): 100 mm (4 in)

Single-Injection vs. Continuous Infusion

Catheter benefits include prolonged analgesia, improved rehabilitation participation, and improved patient satisfaction

Block Room

Ensure proper equipment and medication availability
Monitor patients who receive regional anesthesia until sensory and motor function return

Keys to Success

Anesthesia team and technique
Preoperative management and patient selection
Patient education and surgeon cooperation
Intraoperative management
Postoperative management
Proficiency of clinician and knowledge of equipment
Local anesthetic solution and infection control

Acronym for Success: SCANNING

Supplies
Comfortable positioning
Ambiance
Name and procedure
Nominate a transducer
Infection control
Note lateral/medial side on screen
Gain and depth adjustments

Local Anesthetics

Sensory vs. motor blockade
Continuous interscalene block vs. single-injection interscalene block vs. local infiltration
Comparing pain relief and side-effect profiles

Programmed Intermittent Bolus

Provides optimal delivery of local anesthetics through peripheral nerve catheters
Improves analgesia, reduces VAS scores, and minimizes rescue opioid use
Recognizes variable patterns of efficacy depending on anatomic location

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Description

Review the anatomy of pain, including the somatosensory system, peripheral nervous system, spinal cord, and brain. Learn about afferent neurons, ascending and descending pathways, and more.