For prevention and treatment of hypotension during spinal anaesthesia for elective caesarean section, which vasopressor is currently preferred for routine use, and why?

• A Ephedrine, because it preserves maternal cardiac output better
• B Mephentermine, because it has the longest duration of action
• C Phenylephrine infusion, because it produces less fetal acidosis than ephedrine ✓
• D Adrenaline bolus, because it reliably restores uteroplacental perfusion

Explanation

Phenylephrine, given as an infusion titrated to systolic blood pressure, is the standard prophylactic vasopressor for elective caesarean section under spinal anaesthesia. Randomised comparisons show a higher umbilical arterial pH and less neonatal acidosis compared with ephedrine. Ephedrine crosses the placenta readily and stimulates fetal beta-adrenergic receptors, increasing fetal metabolic activity and lactate production. This reverses the older teaching that ephedrine was the drug of choice in pregnancy.

Reference: Miller's Anesthesia, 9th ed.

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