Obstetric Anesthesia
Pregnancy physiology, neuraxial in labor, preeclampsia, PPH, placental disorders, fetal monitoring, neonatal resuscitation. ← Back to Q-Bank
Q1. Preeclampsia antihypertensive choice
A 28-year-old at 34 weeks with preeclampsia has BP 178/112. Magnesium sulfate is initiated. First-line antihypertensive therapy is:
A. Labetalol IV or hydralazine IV (or oral nifedipine if no IV access)
B. Methyldopa IV
C. Esmolol infusion
D. Sodium nitroprusside infusion
E. Nicardipine plus enalapril
Show answer
Answer: A. Labetalol and hydralazine are first-line; oral nifedipine when no IV access. Methyldopa has slow onset and sedation. Nitroprusside generates cyanide and is reserved for refractory cases with invasive monitoring. ACE inhibitors are contraindicated in pregnancy.
Q2. Postpartum hemorrhage sequence in preeclampsia
After oxytocin fails to control uterine atony in a patient with preeclampsia, the next-line agent is:
A. Methylergonovine 0.2 mg IM
B. Carboprost 250 mcg IM
C. Misoprostol 800 mcg PR
D. Tranexamic acid 1 g IV
E. Additional oxytocin bolus
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Answer: B. In preeclampsia, methylergonovine is avoided second-line because of severe vasoconstriction/HTN risk. Sequence in preeclampsia: oxytocin → carboprost → misoprostol → methylergonovine (with extreme caution). Avoid carboprost in asthma (bronchospasm).
Q3. Aortocaval compression
A 38-week parturient lying supine becomes hypotensive, nauseated, and diaphoretic. The most appropriate first action is:
A. IV phenylephrine bolus
B. Left uterine displacement
C. Trendelenburg position
D. Rapid IV fluid bolus
E. Right uterine displacement
Show answer
Answer: B. Supine hypotensive syndrome — IVC compression by gravid uterus. Tilt 15° left lateral or manually displace the uterus to the left. Reverses immediately. Aortocaval compression can reduce CO 10–25% in third trimester.
Q4. MAC in pregnancy
Compared to a non-pregnant patient, MAC for volatile anesthetics in a parturient is:
A. Increased ~20%
B. Decreased ~30–40%
C. Unchanged
D. Increased ~50%
E. Decreased ~10%
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Answer: B. MAC is reduced as much as 40% in the first trimester and remains reduced throughout. Increased progesterone, endorphins. Returns to baseline within hours after delivery.
Q5. FRC and apnea time in pregnancy
A term parturient is more prone to rapid oxygen desaturation during apnea because:
A. Increased FRC and decreased oxygen consumption
B. Decreased FRC (~20%) and increased oxygen consumption (~20%)
C. Decreased FRC with unchanged O₂ consumption
D. Increased FRC with increased O₂ consumption
E. Unchanged FRC, increased dead space
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Answer: B. Term FRC ↓ ~20% (equal decreases in ERV and RV) + O₂ consumption ↑ ~20% (more in labor: +40% stage 1, +75% stage 2). Time to desaturation is dramatically shortened. Always preoxygenate well; consider RSI with cricoid for general anesthesia.
Q6. Magnesium sulfate toxicity
A preeclamptic patient receiving magnesium develops loss of deep tendon reflexes and respiratory effort begins to wane. The expected magnesium level is:
A. 5 mg/dL
B. 8 mg/dL
C. 12 mg/dL
D. 17 mg/dL
E. 25 mg/dL
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Answer: D. Therapeutic range 5–9 mg/dL. DTR loss ≥10 mg/dL, respiratory paralysis 15–20 mg/dL, asystole >25 mg/dL. Antidote: calcium gluconate 1 g IV. Renal failure markedly increases risk. Magnesium potentiates NDNMBDs.
Q7. Category III fetal heart tracing
A category III fetal heart tracing includes:
A. Moderate variability with early decelerations
B. Absent baseline variability with recurrent late decelerations, recurrent variable decelerations, bradycardia, or sinusoidal pattern
C. Mild variable decelerations
D. Tachycardia with moderate variability
E. Marked variability alone
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Answer: B. Category III = abnormal — absent variability and any of: recurrent late decels, recurrent variable decels, bradycardia; OR sinusoidal pattern. Predictive of abnormal fetal acid-base status. Requires intrauterine resuscitation (left lateral, fluids, oxygen, stop oxytocin, consider tocolytic) and delivery preparation.
Q8. Late decelerations etiology
Late decelerations on fetal heart monitoring most likely indicate:
A. Cord compression
B. Head compression
C. Uteroplacental insufficiency
D. Maternal fever
E. Normal fetal sleep
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Answer: C. Late decels: nadir occurs after peak of contraction, gradual onset (≥30 sec). Mechanism: uteroplacental insufficiency → fetal hypoxemia → reflex bradycardia (or direct myocardial depression). Early decels: head compression (vagal). Variable decels: cord compression.
Q9. Amnioinfusion
Amnioinfusion for recurrent variable decelerations is contraindicated in patients with:
A. Twin pregnancy
B. History of uterine surgery (risk of rupture)
C. Polyhydramnios
D. Maternal diabetes
E. Anti-D antibody
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Answer: B. Saline infusion into amniotic sac relieves cord compression. Contraindicated with prior uterine surgery (rupture risk). First-line for recurrent variables is maternal repositioning to left lateral.
Q10. Placenta accreta risk
Placenta accreta risk is highest with:
A. Previous c-section + placenta previa
B. Multiparity alone
C. Maternal diabetes
D. Twin gestation
E. Polyhydramnios
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Answer: A. Prior c-section + previa: accreta risk rises with each prior c-section (1 prior: 3%, 4+ prior: >60%). Plan: cesarean hysterectomy at 34–36 weeks; large-bore IVs, a-line, blood available, cell salvage, possible IR balloon catheters, multidisciplinary team. PPH and accreta are the leading causes of peripartum hysterectomy.
Q11. Vasa previa diagnosis and timing
Vasa previa is best managed by:
A. Expectant management with weekly NSTs
B. Antenatal diagnosis via transvaginal Doppler ultrasound and scheduled cesarean delivery at 34–37 weeks before ROM
C. Vaginal delivery with continuous monitoring
D. Tocolysis until 40 weeks
E. Routine cesarean at 39 weeks
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Answer: B. Vasa previa: fetal vessels traverse the membranes over the cervical os — ROM can exsanguinate the fetus. Antenatal diagnosis on TVUS; scheduled cesarean at 34–37 weeks before ROM. Classic presentation if undiagnosed: painless vaginal bleeding at ROM with sinusoidal FHR or bradycardia → emergent cesarean.
Q12. Hypertension in pregnancy first-line agents
First-line antihypertensives in pregnancy for chronic hypertension include all EXCEPT:
A. Labetalol
B. Methyldopa
C. Nifedipine
D. Hydralazine
E. Enalapril
Show answer
Answer: E. "Never feed a lab baby hydra and meth." ACE inhibitors and ARBs are contraindicated in pregnancy (renal agenesis, hypocalvaria, fetal demise). Labetalol, methyldopa, nifedipine, hydralazine are safe.
Q13. Amniotic fluid embolism
A laboring patient suddenly develops dyspnea, hypotension, hypoxemia, then cardiovascular collapse and DIC. The mechanism of cardiopulmonary collapse is:
A. Mechanical obstruction of pulmonary vasculature by amniotic fluid alone
B. Massive immunologic and inflammatory response with biphasic acute pulmonary hypertension and LV failure followed by DIC
C. Anaphylaxis to fetal antigens
D. Sudden pulmonary embolism
E. Reflex vasovagal collapse
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Answer: B. AFE is biphasic: acute pulmonary HTN → RV failure → biventricular failure → DIC. Treatment: ACLS, A-OK protocol (atropine, ondansetron, ketorolac is one proposed regimen), aggressive blood product replacement, consider ECMO. Mortality 20–60%.
Q14. Placental drug transfer
Which of the following crosses the placenta most readily?
A. Heparin
B. Glycopyrrolate
C. Insulin
D. Atropine
E. Succinylcholine
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Answer: D. Mnemonic for drugs that don't cross: "He Is Going Nowhere Soon" — Heparin, Insulin, Glycopyrrolate, NMDA (succinylcholine, non-depolarizing NMBDs). Atropine and most other anesthesia drugs cross readily (LoV BABE PONS — locals, volatiles, benzos, atropine, β-blockers, ephedrine, propofol, opioids, neostigmine, scopolamine).
Q15. Glycopyrrolate vs atropine in pregnancy
When reversing neuromuscular blockade in a parturient, which anticholinergic should be paired with neostigmine?
A. Glycopyrrolate (it doesn't cross the placenta)
B. Atropine (neostigmine crosses the placenta — atropine matches to prevent fetal bradycardia)
C. Either is appropriate
D. Scopolamine
E. No anticholinergic is needed
Show answer
Answer: B. Neostigmine crosses the placenta; glycopyrrolate does not → can leave the fetus exposed to muscarinic effects. Atropine crosses placenta and protects the fetus from bradycardia.
Q16. Bupivacaine cardiotoxicity in pregnancy
Why is bupivacaine considered safer than lidocaine in the parturient despite being more cardiotoxic in general?
A. Bupivacaine is rapidly metabolized by plasma cholinesterase
B. Higher protein binding and pKa limit transplacental transfer
C. Bupivacaine has lower lipid solubility
D. Bupivacaine is reversible with naloxone
E. Bupivacaine is hydrophilic
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Answer: B. Bupivacaine pKa 8.1 → mostly ionized at physiologic pH; high protein binding (95%) → less placental transfer. Lidocaine has lower protein binding and can be ion-trapped in fetal acidosis → toxicity. Ropivacaine combines high protein binding with lower cardiotoxicity than bupivacaine.
Q17. Stages of labor pain pathways
Pain during the second stage of labor is mediated primarily by which nerve roots?
A. T10–L1 via hypogastric plexus
B. T12–L1 plus S2–S4 via pudendal nerve
C. T6–T9 via splanchnic nerves
D. L2–L4 via lumbar plexus
E. S1–S3 via pudendal nerve only
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Answer: B. Stage 1 (cervical/uterine): T10–L1 visceral via hypogastric plexus. Stage 2 (perineal stretch): T12–L1 + S2–S4 via pudendal. Epidural for stage 1 may not cover sacral roots fully → consider saddle block or epidural top-up for stage 2.
Q18. Test dose
The classic test dose for an epidural catheter is 3 mL of lidocaine 1.5% with epinephrine 5 mcg/mL. Why epinephrine?
A. Prolongs the duration of the test dose
B. Reduces systemic absorption
C. Intravascular injection produces ↑HR (>20 bpm) within 30–45 sec
D. Identifies subdural placement
E. Identifies subarachnoid placement
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Answer: C. Epinephrine in test dose detects intravascular injection (HR rise >20 bpm). Lidocaine identifies subarachnoid placement (rapid dense block of legs). In laboring patients on β-blockers or with frequent contractions, the HR response is less reliable.
Q19. Hemodynamic changes peak
Maternal cardiac output reaches its highest level:
A. End of 1st trimester
B. End of 2nd trimester
C. End of 3rd trimester
D. Immediately after delivery (autotransfusion)
E. 6 weeks postpartum
Show answer
Answer: D. CO rises 35% by end of 1st trimester, 50% by end of 3rd. During labor, +40% in stage 2; immediately post-delivery, CO peaks (~80% above prelabor) due to autotransfusion from contracting uterus + relief of IVC compression. Important in patients with fixed cardiac lesions (severe MS, AS, PHTN) — peak risk is immediately post-delivery, not at delivery.
Q20. Difficult airway in pregnancy
Compared to non-pregnant, difficult intubation in the parturient is more common because of:
A. Decreased FRC
B. Airway mucosal edema, capillary engorgement, large tongue, enlarged breasts, weight gain
C. Decreased gastric emptying
D. Decreased esophageal sphincter tone
E. Increased aspiration risk
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Answer: B. All true factors but B addresses the intubation difficulty. Use smaller ETT (6.0–6.5), ramp the patient, have video laryngoscope and supraglottic airway ready, preoxygenate aggressively. Mallampati scores typically worsen during labor and pushing.
Q21. Aspiration prophylaxis
For elective cesarean delivery, recommended aspiration prophylaxis includes:
A. Sodium citrate alone
B. Metoclopramide + H₂ blocker (e.g., famotidine) + sodium citrate
C. Omeprazole alone the night before
D. NPO 12 hours
E. Cricoid pressure alone
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Answer: B. Multimodal: H₂ blocker reduces gastric acid secretion; metoclopramide promotes gastric emptying and increases LES tone; sodium citrate (a non-particulate antacid) raises gastric pH immediately. Cricoid pressure is controversial.
Q22. Massive transfusion protocol in PPH
In massive obstetric hemorrhage, the recommended ratio of packed RBC : FFP : platelets is:
A. 4:1:1
B. 1:1:1
C. 6:2:1
D. 2:1:0
E. 1:0:1
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Answer: B. Balanced 1:1:1 resuscitation (PROPPR trial — non-obstetric trauma, extrapolated). In OB, also early fibrinogen replacement (cryo at fibrinogen <200) and TXA within 3 hours of bleeding onset (WOMAN trial: 1g TXA → reduced death from bleeding). Recombinant factor VIIa after multiple rounds of MTP if refractory.
Q23. von Willebrand disease in pregnancy
A 28-year-old G2P1 with type 1 vWD is admitted in active labor. Factor VIII level returns at 60% (well-compensated). The most appropriate plan is:
A. Avoid neuraxial; proceed with general anesthesia for any required cesarean
B. Neuraxial anesthesia is acceptable; DDAVP if needed for active bleeding
C. Continuous epidural with vWF concentrate prophylaxis
D. Prophylactic platelet transfusion
E. Cryoprecipitate before any procedure
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Answer: B. Type 1 vWD is often well-compensated by 3rd trimester (factor VIII and vWF rise). Neuraxial OK if factor VIII >50%. DDAVP releases vWF from endothelium (avoid in type IIB — thrombocytopenia). Type III: vWF concentrate. AVOID neuraxial in untreated severe disease.
Q24. Neonatal resuscitation HR threshold
According to NRP, chest compressions in a newborn are initiated when:
A. HR <100 despite stimulation
B. HR <60 despite 30 seconds of adequate PPV with supplemental oxygen
C. HR <80 after birth
D. HR <120 with apnea
E. Immediately at delivery for premature infants
Show answer
Answer: B. HR <60 after 30 sec of effective PPV → compressions at 3:1 ratio with ventilation (90 compressions : 30 breaths/min). Epinephrine 10–30 mcg/kg IV q3–5 min if HR remains <60 after 30 sec of chest compressions + ventilation.
Q25. Umbilical cord gas interpretation
Normal umbilical arterial cord gas (vs. venous):
A. pH 7.40, PaO₂ 80, PaCO₂ 40
B. pH 7.25, PaO₂ 16–20, PaCO₂ 50
C. pH 7.10, PaO₂ 10, PaCO₂ 60
D. pH 7.35, PaO₂ 40, PaCO₂ 35
E. pH 7.30, PaO₂ 30, PaCO₂ 30
Show answer
Answer: B. Umbilical artery: pH ~7.25, PO₂ 16–20, PCO₂ ~50, BE −4. Umbilical vein: pH ~7.35, PO₂ ~30, PCO₂ ~40. Fetal scalp pH <7.20 suggests fetal acidosis. Fetal P50 ~19 mmHg (vs. adult 27) — high-affinity HbF facilitates placental O₂ transfer.
Q26. Tocolytic contraindications
Indomethacin should be avoided as a tocolytic after which gestational age?
A. 24 weeks
B. 28 weeks
C. 32 weeks
D. 34 weeks
E. 37 weeks
Show answer
Answer: C. Indomethacin >32 wk risks premature ductus arteriosus closure (PG synthesis inhibition). Magnesium: avoid in myasthenia gravis; prolonged use (>5–7 days) → neonatal hypocalcemia/osteopenia. Nifedipine: avoid in AV block or pulmonary edema. Terbutaline: hyperglycemia, maternal tachycardia.
Q27. Cervical cerclage anesthesia
A 19-week parturient presents for prophylactic cervical cerclage. The preferred anesthetic is:
A. Spinal with bupivacaine to T10
B. General anesthesia with sevoflurane and RSI
C. Local infiltration only
D. Lumbar epidural to T6
E. Saddle block to S4
Show answer
Answer: A. Prophylactic cerclage = spinal anesthesia (mid-lumbar) to T10–S4 is well-suited. Emergent cerclage with bulging membranes → general anesthesia preferred (avoids increased intraabdominal/intrauterine pressure, allows uterine relaxation with volatile). RSI if >18–20 weeks gestation.
Q28. Plasma volume expansion
By term, maternal plasma volume has expanded by approximately:
A. 10%
B. 20%
C. 30%
D. 45–50%
E. 70%
Show answer
Answer: D. Plasma volume ↑45–50%; RBC volume ↑25–30% → "physiologic anemia of pregnancy." Fibrinogen, factors VII, VIII, IX, X, XII all rise → hypercoagulable. Factors XI, XIII and antithrombin III fall. PT and PTT shorten ~20%.
Q29. Spinal hypotension management
Spinal hypotension during cesarean is best managed with:
A. Rapid crystalloid bolus alone
B. Co-loading with crystalloid + phenylephrine infusion or boluses; left uterine displacement
C. Trendelenburg only
D. Ephedrine as first-line
E. Vasopressin
Show answer
Answer: B. Phenylephrine is now preferred over ephedrine for spinal hypotension in cesarean (lower fetal acidemia in CONSORT trials). Co-loading (rapid IV fluid at time of spinal) > pre-loading. Maintain LUD.
Q30. PDPH risk factors
The risk of post-dural puncture headache is highest in which patient?
A. 65-year-old male undergoing spinal with 27G pencil-point
B. 28-year-old female parturient who had an unintentional dural puncture with a 17G Tuohy
C. Obese 50-year-old female with 25G Quincke spinal
D. 35-year-old male with prior uneventful spinal
E. Pediatric patient with 22G pencil-point
Show answer
Answer: B. Highest risk: pregnant, young (<40), female, large-bore cutting needle. PDPH after Tuohy dural puncture rate is 50–80%. Pencil-point needles (Sprotte, Whitacre) and 25–27G reduce risk. Treatment: hydration, caffeine, abdominal binder; epidural blood patch is gold standard if conservative measures fail >24–48 hr.
Q31. Anticoagulation and neuraxial in pregnancy
A parturient on prophylactic LMWH (enoxaparin 40 mg subq daily) needs an epidural. Per ASRA, the minimum interval from last dose to needle placement is:
A. 4 hours
B. 8 hours
C. 12 hours
D. 24 hours
E. 48 hours
Show answer
Answer: C. Prophylactic LMWH: wait 12 hr. Therapeutic LMWH: wait 24 hr. After needle placement, restart prophylactic LMWH ≥12 hr later; restart therapeutic ≥24 hr later. Catheter removal: 12 hr after last prophylactic dose; next dose ≥4 hr after removal.
Q32. Stage 1 hemorrhage definition
Per ACOG, postpartum hemorrhage is defined as cumulative blood loss of:
A. >500 mL after any delivery
B. >1000 mL regardless of mode, OR signs of hypovolemia within 24 hr of delivery
C. >2000 mL after cesarean only
D. >300 mL with hypotension
E. Any loss in a coagulopathic patient
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Answer: B. ACOG (2017) revised definition: cumulative blood loss ≥1000 mL or signs/symptoms of hypovolemia within 24 hr of delivery. Etiology — the "4 T's": Tone (atony, most common), Trauma (lacerations, rupture), Tissue (retained placenta, accreta), Thrombin (coagulopathy, DIC).