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Oxygen delivery in shock — FRCA Primary MCQ

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HardPhysiologyOxygen delivery in shockFRCA Primary

A septic patient has Hb 72 g/L, SaO2 98%, cardiac output 3 L/min and lactate 6 mmol/L despite adequate ventilation. Which variable would most directly increase systemic oxygen delivery?

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

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Correct answer: A — Increasing cardiac output

Oxygen delivery is the product of cardiac output and arterial oxygen content, so increasing cardiac output directly raises delivery when saturation is already high. Reducing haemoglobin or saturation would reduce oxygen content. Increased extraction may reflect compensation but does not improve delivery. In shock, circulation and haemoglobin can be more limiting than PaO2.

Reference: West Respiratory Physiology; Ganong Review of Medical Physiology