CAA CAA Regional & Neuraxial Anesthesia 2 — Questions and Answers
Question 1: The epidural space is most accurately identified using the loss-of-resistance (LOR) technique. What substance should be used for LOR to minimize risk of air embolism?
- Air
- Saline (preservative-free) (Correct answer)
- CO2
- Contrast dye
Correct answer: Saline (preservative-free)
Preservative-free saline is the preferred medium for LOR because air can cause pneumocephalus, patchy blocks, or venous air embolism if injected intravascularly.
Question 2: An epidural test dose typically contains epinephrine to detect:
- Intrathecal injection via sudden dense motor block
- Intravascular injection via a heart rate increase of ≥20 bpm within 60 seconds (Correct answer)
- Subdural injection via delayed onset of anesthesia
- Allergic reaction to the local anesthetic
Correct answer: Intravascular injection via a heart rate increase of ≥20 bpm within 60 seconds
Intravascular injection of the epinephrine marker (typically 15 mcg) causes a transient tachycardia within 30–60 seconds, indicating catheter misplacement into a vein.
Question 3: Epidural analgesia for labor pain is typically targeted to cover which dermatomal levels?
- C4–T2
- T10–L1 (first stage) expanding to S2–S4 (second stage) (Correct answer)
- L1–L4 only
- T4–T10 throughout labor
Correct answer: T10–L1 (first stage) expanding to S2–S4 (second stage)
First-stage labor pain is visceral (T10–L1); as delivery approaches, the block is extended caudally to cover S2–S4 for second-stage somatic perineal pain.
Question 4: Which complication is most commonly associated with epidural catheter placement?
- Epidural abscess
- Unintentional dural puncture (wet tap) (Correct answer)
- Spinal cord injury
- Permanent paralysis
Correct answer: Unintentional dural puncture (wet tap)
Unintentional dural puncture occurs in approximately 0.5–2% of epidural placements and is the most common serious complication, often leading to PDPH.
Question 5: Local anesthetic systemic toxicity (LAST) following epidural injection most commonly presents first as:
- Bradycardia and hypotension
- Central nervous system excitation (metallic taste, tinnitus, perioral numbness, seizures) (Correct answer)
- Anaphylaxis with urticaria
- Respiratory depression and apnea
Correct answer: Central nervous system excitation (metallic taste, tinnitus, perioral numbness, seizures)
CNS excitatory signs (circumoral numbness, tinnitus, metallic taste, agitation, then seizures) typically precede cardiovascular collapse in LAST.
Question 6: The first-line treatment for local anesthetic systemic toxicity (LAST) with cardiovascular collapse is:
- Epinephrine 1 mg IV bolus
- 20% lipid emulsion (Intralipid) 1.5 mL/kg IV bolus (Correct answer)
- Sodium bicarbonate IV push
- Calcium chloride IV
Correct answer: 20% lipid emulsion (Intralipid) 1.5 mL/kg IV bolus
20% lipid emulsion acts as a 'lipid sink,' sequestering the lipophilic local anesthetic from cardiac tissue and is the specific antidote for LAST.
CAA CAA Regional & Neuraxial Anesthesia 2
The epidural space is most accurately identified using the loss-of-resistance (LOR) technique.
What substance should be used for LOR to minimize risk of air embolism?