Obstetric Anesthesia
Core concepts
Understand the physiologic changes of pregnancy: increased blood volume and cardiac output, decreased functional residual capacity, increased oxygen consumption, and the risk of rapid desaturation. Know the indications, contraindications, and complications of neuraxial labor analgesia and anesthesia for cesarean delivery. Master the management of preeclampsia and eclampsia, including magnesium sulfate toxicity and its antidote (calcium gluconate). Understand the anesthetic implications of hemorrhage, placenta accreta, and amniotic fluid embolism. Know the approach to the difficult airway in pregnancy and the physiology of aortocaval compression. Recognize local anesthetic toxicity risk and the importance of left uterine displacement.
Traps in questions
- Forgetting that pregnancy reduces local anesthetic requirement and increases the risk of high block.
- Missing that magnesium sulfate potentiates neuromuscular blockade and can cause respiratory depression.
- Confusing preeclampsia with chronic hypertension; proteinuria and end-organ involvement define the former.
- Overlooking that aortocaval compression occurs from about 20 weeks and that left uterine displacement is the fix.
- Assuming an epidural is contraindicated in all preeclamptic patients; it is often preferred if coagulation is acceptable.
Worked example / rule of thumb
A preeclamptic patient on magnesium develops loss of deep tendon reflexes and respiratory depression: stop magnesium and give calcium gluconate. Rule of thumb: in any pregnant patient beyond 20 weeks with hypotension, displace the uterus left before giving vasopressors.
Exam framing
Questions often ask the safest anesthetic for a given obstetric scenario. Consider maternal airway risk, coagulation status, and fetal status; neuraxial techniques are usually preferred when not contraindicated.