Regional Anesthesia and Pain Management Flashcards

Which spinal cord tract is primarily responsible for transmission of nociceptive and temperature signals?

Answer: Spinothalamic tract (anterolateral system)

The spinothalamic tract crosses at the level of entry within 1-2 spinal segments and ascends contralaterally in the anterolateral funiculus to transmit pain, temperature, and crude touch to the thalamus.

During epidural anesthesia, the 'loss of resistance' technique identifies needle entry into which space?

Answer: Epidural space

The epidural space is a negative-pressure potential space containing fat and venous plexuses; resistance to injection through ligamentum flavum gives way to easy injection upon entering this space.

Gabapentin and pregabalin produce analgesia in neuropathic pain primarily by binding to which receptor subunit?

Answer: Alpha-2-delta subunit of voltage-gated calcium channels

Gabapentinoids bind to the alpha-2-delta-1 subunit of voltage-gated calcium channels on presynaptic neurons, reducing calcium influx and decreasing release of excitatory neurotransmitters like glutamate and substance P.

A 45-year-old presents with lancinating pain along the T5 dermatome following herpes zoster infection 6 months ago. What is the most accurate diagnosis?

Answer: Post-herpetic neuralgia (PHN)

Post-herpetic neuralgia is defined as pain persisting in the distribution of herpes zoster beyond 90 days after acute infection onset, characterized by lancinating, burning, or allodynic pain.

Which landmark defines the level of the conus medullaris in adults and guides safe intrathecal injection?

Answer: L1-L2 interspace

In adults, the conus medullaris typically ends at L1-L2; spinal anesthesia is most safely performed at L3-L4 or L4-L5 to avoid direct cord trauma.

What is the mechanism by which neuraxial opioids cause delayed respiratory depression?

Answer: Rostral migration in cerebrospinal fluid reaching brainstem respiratory centers

Hydrophilic opioids like morphine injected intrathecally or epidurally undergo rostral CSF migration to reach mu-receptors in the brainstem (pre-Bötzinger complex), causing delayed respiratory depression 6-12 hours post-injection.

Which parameter best guides adequacy of sympathetic blockade during spinal anesthesia?

Answer: Loss of cold sensation (temperature discrimination)

Sympathetic block extends approximately 2 dermatomes higher than sensory block; temperature discrimination (cold testing) detects the highest level of blockade because A-delta cold fibers are blocked first.