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Module 10 · Anaesthesia Blueprints

Obstetric anaesthesia: exam notes and MCQs

Prepare obstetric anaesthesia for postgraduate anaesthesia examinations with structured notes, exam-style questions and referenced explanations from standard textbooks and current guidelines.

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Exam notes in this module

Physiology of pregnancy and anaesthesia for caesarean section
Maternal adaptations, neuraxial and general anaesthesia, and postpartum haemorrhage.
Pre-eclampsia, eclampsia and HELLP
Definitions, pathophysiology, severity, magnesium, blood pressure control and anaesthetic management.
Labour analgesia
Pain pathways, non-pharmacological and systemic options, neuraxial techniques and complications.

Sample questions

Q1. Preferred first-line vasopressor for spinal-induced hypotension during caesarean section is:

  1. Ephedrine bolus
  2. Phenylephrine
  3. Atropine
  4. Dopamine
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Answer B: Phenylephrine

Consensus guidelines favour prophylactic phenylephrine infusion (or norepinephrine) because it avoids fetal acidosis seen with ephedrine; treat bradycardia with glycopyrrolate.

Exam style: AIIMS INI-SS

Q2. In a patient on MgSO₄ for severe pre-eclampsia, the EARLIEST clinical sign of magnesium toxicity is:

  1. Respiratory depression
  2. Loss of deep tendon reflexes
  3. Cardiac arrest
  4. Prolonged QT interval
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Answer B: Loss of deep tendon reflexes

Magnesium toxicity follows a predictable sequence as plasma levels rise. Therapeutic range ≈ 2–3.5 mmol/L (4–7 mEq/L, 4.8–8.4 mg/dL). Non-specific symptoms (warmth, flushing, nausea, drowsiness, diplopia, slurred speech) may appear first, but they are subjective; the EARLIEST OBJECTIVE sign — and the one monitored at the bedside — is loss of deep tendon (patellar) reflexes at ≈ 3.5–5 mmol/L (7–10 mEq/L), with PR prolongation and QRS widening. Respiratory paralysis follows at ≈ 5–6.5 mmol/L (10–13 mEq/L) and cardiac arrest above ≈ 12.5 mmol/L (25 mEq/L). Units: 1 mmol/L = 2 mEq/L ≈ 2.4 mg/dL.

Exam style: AIIMS INI-SS

Q3. Uterine blood flow at term is approximately:

  1. 100 mL/min (2% of cardiac output)
  2. 300 mL/min (5% of cardiac output)
  3. 700–900 mL/min (≈ 10% of cardiac output)
  4. 1500 mL/min (25% of cardiac output)
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Answer C: 700–900 mL/min (≈ 10% of cardiac output)

Uterine blood flow rises from about 100 mL/min in the non-pregnant state to 700–900 mL/min (≈ 10% of cardiac output) at term. The uteroplacental bed is maximally dilated and does NOT autoregulate, so flow is pressure-dependent: maternal hypotension, aortocaval compression and uterine contractions directly reduce it.

Exam style: NEET-SS Anaesthesia

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