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Haemorrhage Compensation — FRCA Primary MCQ

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HardPhysiology - CardiovascularHaemorrhage CompensationFRCA Primary

Immediately after an acute 15% blood-volume loss, which response has the shortest latency and contributes directly to maintenance of arterial pressure?

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Correct answer: C — Reduced carotid-baroreceptor firing with increased sympathetic vasomotor outflow

The best answer is “Reduced carotid-baroreceptor firing with increased sympathetic vasomotor outflow”. Reduced arterial stretch decreases baroreceptor firing within seconds, increasing sympathetic tone, heart rate, contractility, arteriolar resistance and venous tone. Renin–angiotensin and vasopressin responses contribute later; aldosterone-mediated sodium retention is slower still. Erythropoiesis and protein synthesis are delayed adaptive responses rather than immediate pressure support.

Reference: RCoA, Primary FRCA syllabus: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf; Pathophysiology of Hemorrhage as It Relates to the Warfighter: https://pmc.ncbi.nlm.nih.gov/articles/PMC8977138/