BCA Obstetric Anesthesia & Analgesia 2 — Questions and Answers
Question 1: Which uteroplacental circulation characteristic makes the fetus vulnerable to maternal hypotension during neuraxial anesthesia?
- Uteroplacental blood flow is pressure-dependent with no autoregulation (Correct answer)
- Placental vasculature has robust autoregulation similar to cerebral circulation
- Fetal hemoglobin has lower oxygen affinity than maternal hemoglobin
- Uterine arteries have alpha-2 receptors that cause vasodilation
Correct answer: Uteroplacental blood flow is pressure-dependent with no autoregulation
Uteroplacental blood flow lacks autoregulation and is directly dependent on maternal perfusion pressure, making the fetus vulnerable to maternal hypotension.
Question 2: A parturient at 38 weeks gestation requires emergency cesarean delivery under general anesthesia. Which agent is MOST appropriate for rapid sequence induction?
- Etomidate 0.3 mg/kg
- Propofol 2 mg/kg
- Ketamine 1-1.5 mg/kg (Correct answer)
- Thiopental 4-5 mg/kg
Correct answer: Ketamine 1-1.5 mg/kg
Ketamine 1–1.5 mg/kg is preferred for RSI in obstetrics when propofol is avoided; it maintains hemodynamics and is safe for the fetus.
Question 3: What is the primary mechanism by which epidural labor analgesia reduces maternal catecholamine levels?
- Direct adrenal suppression by local anesthetics
- Interruption of pain-mediated sympathetic activation (Correct answer)
- Alpha-2 agonist effect of opioids added to the epidural
- Systemic absorption of local anesthetic reducing adrenal output
Correct answer: Interruption of pain-mediated sympathetic activation
Pain relief from epidural analgesia interrupts the sympathoadrenal reflex arc, reducing pain-driven catecholamine release and improving uteroplacental blood flow.
Question 4: During labor epidural top-up for emergency cesarean, which local anesthetic produces the fastest surgical anesthesia onset?
- Bupivacaine 0.5%
- Ropivacaine 0.75%
- Chloroprocaine 3% (Correct answer)
- Lidocaine 1%
Correct answer: Chloroprocaine 3%
Chloroprocaine 3% has the fastest onset (2–5 minutes) of all epidural local anesthetics due to its high pKa offset by high concentration and rapid hydrolysis.
Question 5: A term parturient develops high spinal block after epidural catheter migration. Which hemodynamic intervention is FIRST-LINE?
- Phenylephrine 100 mcg IV bolus (Correct answer)
- Ephedrine 5-10 mg IV bolus
- Norepinephrine infusion at 0.1 mcg/kg/min
- Dopamine 5 mcg/kg/min IV infusion
Correct answer: Phenylephrine 100 mcg IV bolus
Phenylephrine is the first-line vasopressor for spinal-induced hypotension in obstetrics as it restores SVR with less fetal acidosis than ephedrine.
Question 6: Which parameter BEST guides the adequacy of a spinal block before cesarean delivery?
- Loss of cold sensation to T4 bilaterally (Correct answer)
- Loss of pinprick to T6 bilaterally
- Motor block of the lower extremities
- Patient report of numbness to the umbilicus
Correct answer: Loss of cold sensation to T4 bilaterally
Cold sensation testing to T4 (nipple line) is the standard clinical assessment ensuring adequate block height for uterine manipulation and peritoneal stimulation.
Question 7: Intrathecal morphine 0.1-0.2 mg after cesarean delivery primarily provides analgesia by acting on which receptors?
- Mu opioid receptors in the substantia gelatinosa of the dorsal horn (Correct answer)
- Kappa receptors in the supraspinal centers
- Delta receptors in peripheral sensory neurons
- Mu receptors at the dorsal root ganglion
Correct answer: Mu opioid receptors in the substantia gelatinosa of the dorsal horn
Intrathecal morphine binds mu opioid receptors in the spinal cord dorsal horn, producing prolonged neuraxial analgesia lasting 12–24 hours.
BCA Obstetric Anesthesia & Analgesia 2
Which uteroplacental circulation characteristic makes the fetus vulnerable to maternal hypotension during neuraxial anesthesia?