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Metaraminol vasopressor action — FRCA Primary MCQ

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HardPharmacologyMetaraminol vasopressor actionFRCA Primary

A healthy woman undergoing spinal anaesthesia for Caesarean birth becomes hypotensive with a heart rate of 92/min. A small bolus of metaraminol is given. Which effect best explains the rise in blood pressure?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Predominant α1-mediated vasoconstriction

Metaraminol acts predominantly through α1-mediated vasoconstriction, with some indirect noradrenaline release, increasing systemic vascular resistance. β2-mediated bronchodilatation is not its useful vasopressor mechanism. Dopamine receptor stimulation and nitric oxide release would not produce the desired effect here. In obstetric spinal hypotension, vasopressors are chosen to restore maternal pressure and uteroplacental perfusion.

Reference: Peck, Hill & Williams Pharmacology for Anaesthesia and Intensive Care; Obstetric anaesthesia textbooks