Regional Anesthesia
Brachial plexus blocks, neuraxial anesthesia, peripheral nerve blocks, complications. ← Back to Q-Bank
Q1. PDPH treatment
A 31-year-old develops a positional frontal-occipital headache 36 hours after an attempted epidural with multiple dural punctures. Conservative measures have failed. The most definitive treatment is:
A. Oral caffeine 300 mg every 6 hours
B. IV cosyntropin
C. Sumatriptan 6 mg SC
D. Epidural blood patch (~20 mL autologous blood)
E. Sphenopalatine ganglion block
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Answer: D. Epidural blood patch is the gold standard (60–90% efficacy on first attempt). Risk factors for PDPH: age <40, female, prior history, large-bore cutting (Quincke) > pencil-point (Sprotte, Whitacre), loss-of-air technique vs. saline. Sphenopalatine ganglion block is an emerging alternative.
Q2. Interscalene block nerve sparing
After an interscalene brachial plexus block, the patient can still feel his ulnar fingers. The most likely reason is:
A. Failed block
B. The interscalene approach commonly spares C8–T1 (ulnar) distribution
C. Local anesthetic too dilute
D. Anatomic variant
E. Patient hyperalgesia
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Answer: B. Interscalene blocks the upper trunk and middle trunk of the brachial plexus (C5–C7) and commonly spares the inferior trunk (C8–T1) — the ulnar distribution. Best for shoulder surgery, NOT hand surgery. Expect ipsilateral phrenic nerve blockade in ~100% (avoid in severe pulmonary disease), recurrent laryngeal nerve block (hoarseness), and Horner syndrome.
Q3. Supraclavicular block complication
The most concerning complication of a supraclavicular brachial plexus block is:
A. Phrenic nerve palsy
B. Horner syndrome
C. Pneumothorax
D. Recurrent laryngeal nerve block
E. Hoarseness
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Answer: C. Supraclavicular block has a 1–6% PTX risk (the most serious). Phrenic nerve blockade ~50% (most common). Performed at trunks/divisions level of brachial plexus. U/S has significantly reduced PTX risk but not eliminated it. Best for surgery distal to mid-humerus.
Q4. Axillary block sparing
An axillary brachial plexus block frequently misses which nerve?
A. Median
B. Ulnar
C. Radial
D. Musculocutaneous
E. Median antebrachial cutaneous
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Answer: D. The musculocutaneous nerve exits the axillary sheath above the level of axillary block injection (within the coracobrachialis muscle). Always supplement with a separate injection into the coracobrachialis between biceps and triceps. Axillary block targets median, ulnar, radial (ARMU around the axillary artery).
Q5. Brachial plexus anatomy by block
The infraclavicular block targets the brachial plexus at the level of:
A. Roots
B. Trunks
C. Divisions
D. Cords
E. Branches
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Answer: D. Interscalene = roots/trunks (C5–C7). Supraclavicular = trunks/divisions. Infraclavicular = cords. Axillary = branches (terminal nerves).
Q6. Femoral nerve block target muscle response
During a femoral nerve block with peripheral nerve stimulation, you observe twitch of the sartorius muscle (medial knee). To capture the main femoral nerve, redirect the needle:
A. Anteromedially
B. Posterolaterally
C. Caudally only
D. Cephalad
E. Withdraw and reposition more medially
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Answer: B. Sartorius twitch indicates anterior branch of femoral nerve. Quadriceps twitch ("patellar snap") is desired — posterior branch. Redirect posterolaterally to reach the main femoral nerve.
Q7. Adductor canal block
The adductor canal block primarily targets the:
A. Femoral nerve (motor)
B. Saphenous nerve (sensory only)
C. Obturator nerve
D. Sciatic nerve
E. Lateral femoral cutaneous nerve
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Answer: B. Adductor canal block targets the saphenous nerve (terminal sensory branch of femoral) — provides knee analgesia while preserving quadriceps strength. Preferred over femoral block for knee arthroplasty to allow early ambulation.
Q8. TAP block coverage
The transversus abdominis plane (TAP) block provides analgesia for dermatomes:
A. T6–T9
B. T9–L1
C. L1–L3
D. T10–S1
E. C8–T2
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Answer: B. TAP block covers T9–L1 (intercostal, subcostal, ilioinguinal, iliohypogastric nerves). Adequate for skin and muscle of anterior abdominal wall but NOT visceral pain. Adjunct to GA. Landmark: triangle of Petit. U/S identifies plane between internal oblique and transversus abdominis.
Q9. Sciatic nerve block components
Both common peroneal and tibial nerves must be blocked for foot anesthesia. They share an origin from:
A. Lumbar plexus
B. Sciatic nerve
C. Femoral nerve
D. Obturator nerve
E. Pudendal nerve
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Answer: B. Sciatic nerve (L4–S3) divides into tibial + common peroneal. Common peroneal → superficial + deep peroneal. Sciatic block: popliteal approach is convenient (block above the divide). Foot also needs saphenous nerve coverage (femoral/lumbar plexus origin) for medial coverage.
Q10. Lumbar plexus block coverage
The lumbar plexus block (Winnie/3-in-1) covers:
A. Femoral, obturator, lateral femoral cutaneous
B. Sciatic and femoral
C. Pudendal and ilioinguinal
D. Genitofemoral only
E. Hypogastric plexus
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Answer: A. Lumbar plexus = ventral rami of L1–L4 + T12. Branches: iliohypogastric (T12–L1), ilioinguinal (L1), genitofemoral (L1–L2), lateral femoral cutaneous (L2–L3), obturator (L2–L4), femoral (L2–L4). Sciatic is not part of lumbar plexus — it's sacral.
Q11. Stellate ganglion block clinical sign
The most reliable indicator of a successful stellate ganglion block is:
A. Horner syndrome
B. Hoarseness
C. Ipsilateral temperature rise
D. Patient report of pain relief
E. Loss of biceps reflex
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Answer: C. Horner syndrome (ptosis, miosis, anhidrosis) develops early but may reflect cephalad spread without complete sympathectomy. Ipsilateral skin temperature increase (>1°C) is the most reliable sign of complete sympathetic block to the upper extremity. Used for CRPS, refractory angina, vascular insufficiency.
Q12. Celiac plexus block
Celiac plexus block is used for analgesia of:
A. Pelvic visceral pain
B. Upper abdominal visceral pain (pancreatic cancer, chronic pancreatitis)
C. Lower extremity ischemic pain
D. Thoracic radicular pain
E. Hepatic capsular pain only
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Answer: B. Celiac plexus block covers upper abdominal viscera (T5–T12 sympathetic innervation): pancreatic cancer pain, chronic pancreatitis. Side effects: hypotension (sympathectomy), diarrhea (parasympathetic dominance), retroperitoneal bleeding, paraplegia from spinal artery spasm.
Q13. Spinal anesthesia in infants
Compared to adults, spinal anesthesia in infants is characterized by:
A. Longer duration of action
B. Higher incidence of hypotension
C. Faster onset and shorter duration of action; rare hypotension
D. Lower volume requirement
E. Requirement of general anesthesia for placement
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Answer: C. Infant spinal: faster onset, shorter duration (~75–90 min with bupivacaine vs. several hours in adults) — higher CO, vascular pia, immature sympathetic system. Rare hypotension. Used for preterm infants <60 weeks PCA to reduce post-op apnea. Dose ~0.8 mg/kg of 0.5% bupivacaine. Caution: cord ends at L3 until age 2.
Q14. Spinal cord termination peds
In a neonate, the spinal cord ends at approximately:
A. L1
B. L3
C. L5
D. S1
E. T12
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Answer: B. Neonate cord ends at L3 (vs. adult L1–L2); reaches adult level by ~2 years. Dural sac ends at S3 (vs. adult S2). Use a more caudal interspace for lumbar puncture in neonates.
Q15. Caudal block dosing
For a caudal epidural in a 12 kg toddler, what volume of 0.25% bupivacaine provides analgesia up to mid-thoracic dermatomes?
A. 0.5 mL/kg
B. 1.0 mL/kg
C. 1.25 mL/kg
D. 2.0 mL/kg
E. 0.25 mL/kg
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Answer: C. Caudal dosing by volume (concentration determines density of block, not height): 0.5 mL/kg = sacral, 1.0 mL/kg = low thoracic, 1.25 mL/kg = mid-thoracic. Common concentrations: 0.125–0.25% bupivacaine or 0.2–0.3% ropivacaine.
Q16. Transient neurologic symptoms
Transient neurologic symptoms after spinal anesthesia are most associated with:
A. Bupivacaine in obstetric patients
B. Lidocaine spinal, lithotomy position, knee arthroscopy, outpatient surgery
C. Ropivacaine in elderly patients
D. Procaine in any patient
E. Mepivacaine epidural
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Answer: B. TNS: buttock/thigh pain after uncomplicated spinal; no objective neuro deficit. Highest risk: hyperbaric 5% lidocaine, lithotomy, knee arthroscopy, outpatient. Self-limited (resolves <72 hr). Not associated with bupivacaine or ropivacaine.
Q17. ASRA — clopidogrel hold
Per ASRA guidelines, clopidogrel must be held how long before neuraxial procedure?
A. 1–2 days
B. 5–7 days
C. 10 days
D. 14 days
E. 30 days
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Answer: B. Clopidogrel: hold 5–7 days. Ticlopidine: 10 days. Prasugrel: 7–10 days. Ticagrelor: 5–7 days. Newer DOACs (apixaban, rivaroxaban): hold 3 days; dabigatran 5 days (more if CrCl reduced).
Q18. ASRA — heparin neuraxial
For a patient on prophylactic subcutaneous unfractionated heparin (5,000 U TID), the minimum interval from last dose to neuraxial needle placement is:
A. 1 hour
B. 4–6 hours
C. 12 hours
D. 24 hours
E. None — proceed immediately
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Answer: B. Prophylactic UFH (peak 1–2 hr, duration 4–6 hr): hold 4–6 hr. Therapeutic IV UFH: 4–6 hr + verify normal coagulation. Restart heparin ≥1 hr after needle placement. If on heparin >4 days, check platelets before block (HIT risk).
Q19. Awake fiberoptic airway block — superior laryngeal
The internal branch of the superior laryngeal nerve provides sensory innervation to:
A. Tongue base, epiglottis, aryepiglottic folds, supraglottis to the vocal cords
B. Trachea below the vocal cords
C. Posterior third of the tongue only
D. Cricothyroid muscle motor
E. False vocal cords motor
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Answer: A. Vagal afferents: internal SLN → supraglottis to cords; recurrent laryngeal → below cords (sensory + motor to all intrinsic muscles except cricothyroid which is external SLN). Block at hyoid for awake fiberoptic intubation: 2 mL 2% lidocaine through thyrohyoid ligament.
Q20. Subdural block
Compared to a spinal, the signs of an unintended subdural injection include:
A. Identical block height and density
B. Patchy, dense sensory block out of proportion to motor block, with greater sympathetic block than expected
C. Block lasting 15 min only
D. Only unilateral block
E. Block confined to sacral dermatomes
Show answer
Answer: B. Subdural injection: dense sensory (posterior fibers) with variable motor (more anterior), unexpectedly high sympathetic block. Slower onset than spinal, faster than epidural. Treat with airway/hemodynamic support; block dissipates over hours.
Q21. Spinal vs epidural for TURP
For transurethral resection of the prostate, spinal anesthesia is generally preferred over GA because:
A. Faster onset
B. Allows monitoring for TURP syndrome (mental status change) in awake patient
C. Avoids fluid overload
D. Eliminates need for cell salvage
E. Prevents Compound A toxicity
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Answer: B. Awake spinal allows monitoring for early TURP syndrome (hyponatremia/glycine toxicity → AMS, nausea, visual changes), bladder/prostatic capsule perforation (shoulder pain, abdominal pain, dyspnea, bradycardia). T10 level: adequate analgesia, pelvic floor relaxation, preserves awareness. Hypothermia from irrigant absorption is also detectable.
Q22. Retrobulbar vs peribulbar block
Compared to retrobulbar block, peribulbar block has:
A. Faster onset
B. Higher rate of central spread (brainstem anesthesia)
C. Lower risk of optic nerve injury and retrobulbar hemorrhage
D. More dense akinesia
E. Lower volume requirement
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Answer: C. Peribulbar: needle stays outside the muscle cone — slower onset (9–12 min), less complete akinesia, but lower risk of optic nerve damage, retrobulbar hemorrhage, and central spread. Both blocks attenuate oculocardiac reflex (V1 trigeminal afferent).
Q23. Bier block (IV regional)
Maximum safe time for tourniquet inflation during a Bier block is:
A. 10 minutes
B. 20 minutes
C. 30–60 minutes
D. 90 minutes
E. 2 hours
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Answer: C. Bier block: inflate tourniquet, inject 0.5% lidocaine (no epinephrine) distal to tourniquet. Minimum tourniquet inflation = 20–25 min (avoid sudden release of LA). Maximum ~60–90 min. Beyond this, ischemic pain limits utility.
Q24. Local anesthetic absorption rank order
From greatest to least systemic absorption after injection:
A. Intercostal > caudal > epidural > brachial plexus > subcutaneous
B. Subcutaneous > epidural > brachial plexus > intercostal
C. Brachial plexus > intercostal > epidural > sciatic
D. Caudal > brachial plexus > intercostal > sciatic
E. Sciatic > epidural > brachial plexus > intercostal
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Answer: A. "ICEBaLLs" or "BICEPS": IV > InterTracheal > Intercostal > Caudal/paracervical > Epidural > Brachial plexus > sciatic/femoral > Subcutaneous. Intercostal absorption is highest of the routine regional techniques — beware in patients near maximum dose.
Q25. Continuous peripheral nerve catheter contraindications
Relative contraindications to an outpatient continuous peripheral nerve catheter include:
A. Severe hepatic/renal insufficiency, infection at site, anticoagulation, infusions affecting phrenic nerve in patients with poor pulmonary reserve
B. Diabetes
C. Age over 65
D. Single-shot block earlier in the day
E. Mild COPD
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Answer: A. Hepatic/renal disease ↑ systemic LA toxicity risk over prolonged infusion. Avoid phrenic-blocking catheters (interscalene) in poor pulmonary reserve. Infection at site is absolute contraindication. Coagulopathy is absolute for deep blocks.
Q26. Local anesthetic mechanism
Local anesthetics produce nerve blockade by:
A. Reversibly blocking voltage-gated sodium channels from the intracellular side
B. Blocking potassium channels
C. Antagonizing GABAₐ receptors
D. Blocking acetylcholine receptors
E. Inhibiting Na/K-ATPase
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Answer: A. LAs bind the intracellular side of voltage-gated Na⁺ channels in the open/inactivated state → prevent depolarization. The unionized form crosses the membrane; the ionized form binds the receptor inside the channel. Faster nerves with higher firing rates are blocked first (use-dependent block). Small unmyelinated > small myelinated > large myelinated (B > C > A delta > A beta > A alpha in vivo, though clinically: sympathetic → cold → pain → touch → motor).