Anesthesiology APPLIED Exam › Obstetric anesthesia

Maternal cardiac arrest and resuscitative hysterotomy

Obstetric anesthesia·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 31-year-old woman, 92 kg, at 34 weeks with preeclampsia with severe features is on a magnesium sulfate infusion in a labor room. She is not in labor and has no epidural. The nurse finds her unresponsive, apneic and pulseless; the monitor shows a slow, wide-complex rhythm. The fundus is well above the umbilicus. You are the first anesthesiologist to arrive, and the operating room is down the hall.

Question

How do you run the first five minutes of this resuscitation?

Ideal answer

HeadlineCardiac arrest: two patients, one plan, high-quality CPR plus delivery by 5 minutes. I call the obstetric code and neonatal team and assign a timer.

Compressions on a backboard; manual left uterine displacement. The uterus is above the umbilicus; caval compression will defeat my compressions.¹
Pads on; shock if shockable, unchanged doses. Fetal monitors off rather than delay a shock.
Bag-mask 100% oxygen, then intubate without stopping compressions. Oral airway first; an experienced person with a 6.0–7.0 tube, supraglottic airway as backup.¹
Access above the diaphragm; standard ACLS drugs; magnesium off. IV or IO; none is contraindicated in pregnancy.¹ Causes read aloud: magnesium toxicity, preeclampsia-related bleeding.
Cesarean pack open now; incision about 4 minutes, here. No return of circulation, delivery by 5;¹^,2 it relieves caval compression, helping the mother first; the baby's survival also depends on speed.

Breaking down the answer

Do not move her — in simulation, only 14% of teams who transported to the OR made incision within 5 minutes, compared with 57% who operated at the site of arrest.¹ Knowing that data shows organization under pressure.
For the mother — the 2025 AHA guidelines replace "perimortem cesarean" with "resuscitative delivery" and say preparation starts when arrest is recognized.² In a 2012 review, only 4 of 76 women were delivered within 5 minutes; delivery helped the mother in 32% and harmed none.¹
Airway: oxygenate first — aspiration risk is real, but oxygenation and ventilation take priority; cricoid pressure is released if it impedes the view or ventilation.¹
The causes checklist — SOAP A-to-H: Anesthetic complications, Bleeding, Cardiovascular, Drugs (including magnesium overdose), Embolic, Fever, General H's and T's, Hypertension; AHA BEAU-CHOPS covers the same ground. Most likely: cardiac disease, hemorrhage, amniotic fluid embolism.¹
Know the rescue — ECPR is reasonable for pregnant or peripartum arrest that does not respond to standard resuscitation; reported survival is 55–75%.²

Follow-up question

As the obstetrician picks up the scalpel, the nurse says the magnesium pump was programmed at 10 g/h instead of 2 g/h for the last three hours, and her reflexes were absent at the last check. What do you do?

Follow-up answer

HeadlineProbable magnesium toxicity as the cause; I tell the team without stopping CPR or the delivery, and confirm the infusion is off.

Absent reflexes and a slow, wide rhythm fit a very high level: reflexes are lost and respiratory paralysis threatens near 10 mEq/L, and higher levels depress cardiac conduction.³ IV calcium now, because a calcium salt is the antidote, and continued ventilation, since she stays apneic until the level falls.³ Delivery proceeds at 4 minutes regardless. Magnesium level, potassium, blood gas. After return of circulation: uterotonics for expected atony and bleeding, sedation and amnesia because awareness is possible, and ICU with MAP at least 65 mmHg and SpO2 94–98%.¹^,4 Renal function decides clearance.

Pitfalls that cost points

Tilting the whole patient instead of manual uterine displacement.
Waiting for 4 minutes of failed CPR before opening the cesarean pack.
Withholding epinephrine, amiodarone or defibrillation because she is pregnant.

Rapid-fire

Q: How common is it? A: Cardiac arrest is estimated to occur in fewer than 1 in 20,000 pregnancies.¹

Q: Do you watch the fetal heart rate during CPR? A: No; fetal monitoring is not needed to guide management and distracts from maternal CPR and delivery.¹

Q: Do you give lipid emulsion if this follows an epidural top-up? A: Yes, as an adjunct at nonpregnant doses if local anesthetic toxicity is suspected.¹

Q: How do you ventilate once intubated? A: About 10 breaths per minute, each over 1 second, without pausing compressions.¹

Q: Does she need uterine displacement before 20 weeks? A: It depends on the circumstances; multiple gestation or polyhydramnios can cause caval compression earlier.¹

Numbers to know

Item	Value
Incidence	Fewer than 1 in 20,000¹
Incision / delivery goal	4 min / 5 min from arrest¹
Manual uterine displacement	Uterus at or above umbilicus¹
Endotracheal tube	6.0–7.0¹
ECPR survival in pregnancy	55–75%²
Magnesium: reflexes lost	~10 mEq/L (about 12 mg/dL), with respiratory paralysis³

Sources

1.SOAP Consensus Statement on the Management of Cardiac Arrest in Pregnancy · SOAP (Lipman et al., Anesth Analg), 2014 · soap.orgTable 1 first-minutes checklist; Table 2 BEAU-CHOPS causes; Section 8 perimortem delivery.
2.Highlights of the 2025 AHA Guidelines for CPR and ECC · AHA, 2025 · cpr.heart.orgResuscitative delivery replaces perimortem cesarean; ECPR in pregnancy (survival 55–75%).
3.Magnesium Sulfate in Water for Injection prescribing information · FDA / DailyMed (Hospira) · dailymed.nlm.nih.govReflexes diminish above 4 mEq/L and are lost near 10 mEq/L with respiratory paralysis; calcium salt as antidote.
4.SMFM Clinical Guideline #9: Amniotic fluid embolism: diagnosis and management · SMFM (Pacheco et al., Am J Obstet Gynecol), 2016 · assets.noviams.comPost-arrest targets: MAP 65 mmHg, SpO2 94–98%.

Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.