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Thermodilution Stewart-Hamilton — FRCA Primary MCQ

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HardPhysiology - CardiovascularThermodilution Stewart-HamiltonFRCA Primary

A pulmonary-artery catheter measures cardiac output after a cold indicator bolus. Which principle underlies this method?

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Correct answer: CThe Stewart Hamilton temperature indicator dilution relationship for cardiac output measurement

The best answer is “The Stewart Hamilton temperature indicator dilution relationship for cardiac output measurement”. Thermodilution is an indicator-dilution technique derived from the Stewart–Hamilton relationship. A known cold bolus is injected into the right heart and the downstream temperature–time curve is integrated; a larger area under the curve represents lower flow. The Fick principle is a different cardiac-output method based on oxygen consumption and arteriovenous oxygen-content difference.

Reference: Resuscitation Council UK, Adult Advanced Life Support Guidelines 2025: https://www.resus.org.uk/cy/node/36438