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High spinal cardiac sympathetic block — FRCA Primary MCQ

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HardPhysiologyHigh spinal cardiac sympathetic blockFRCA Primary

A patient has high spinal anaesthesia with profound hypotension, bradycardia and difficulty breathing. Sensory block is above T2. Which mechanism most directly contributes to bradycardia?

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

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Correct answer: E — Blockade of cardiac accelerator sympathetic fibres

High neuraxial block can interrupt T1-T4 sympathetic cardiac accelerator fibres and reduce venous return, producing bradycardia and hypotension. The vagus nerve itself is not blocked by spinal anaesthesia. Hyperkalaemia is not the direct mechanism. The pearl is that bradycardia during high spinal may herald severe cardiovascular compromise.

Reference: RCoA Primary FRCA Syllabus 2026; Ganong's Review of Medical Physiology; West's Respiratory Physiology