Question:medium

Which is the most characteristic cardiovascular effect of the inhalational anaesthetic halothane?

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Halothane is a myocardial depressant - expect cardiac output and BP to fall with depth.
Updated On: Jun 25, 2026
  • Dose-dependent fall in cardiac output and blood pressure (often a 20-30 mm Hg drop) from myocardial depression
  • Increase in cardiac output with reflex tachycardia
  • Rise in systemic vascular resistance with hypertension
  • No measurable effect on cardiac output or blood pressure
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The Correct Option is A

Solution and Explanation

Halothane is the classic example of an inhalational anaesthetic that depresses the heart directly. Its hallmark cardiovascular signature is a dose-dependent decline in cardiac output and arterial pressure — the deeper the anaesthesia, the greater the depression, with mean pressure often falling by roughly $20\text{--}30$ mm Hg.

The mechanism is reduced myocardial contractility combined with blunting of the baroreceptor reflex, so the expected compensatory tachycardia does not occur; heart rate is typically unchanged or slowed. A second clinically critical property is that halothane sensitises the myocardium to catecholamines, so injected adrenaline or rising $CO_2$ can precipitate ventricular ectopy and arrhythmias.

This profile excludes the other choices: there is no rise in cardiac output, no increase in systemic vascular resistance, and the agent is far from haemodynamically silent — cardiodepression and hypotension are precisely what define it.

\[\boxed{\text{Halothane} \rightarrow \downarrow \text{cardiac output and BP, proportional to depth}}\]
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