Induction Agent Cardiovascular Effects — FRCA Final MCQ

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ModerateGeneral AnaesthesiaInduction Agent Cardiovascular EffectsFRCA Final

A 68-year-old man (ASA IV) with severe mitral regurgitation and pulmonary hypertension requires emergency laparotomy. If each agent were given as a conventional single-agent intravenous induction dose, without prophylactic vasopressor support, which is most likely to cause the greatest immediate reduction in systemic vascular resistance and arterial pressure?

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Correct answer: A — Propofol

Propofol is correct. At conventional induction doses it produces marked arterial and venous vasodilation, suppresses sympathetic outflow and impairs baroreflex compensation, with additional myocardial depression. It causes a greater fall in arterial pressure and systemic vascular resistance than equipotent thiopental. In pulmonary hypertension, abrupt systemic hypotension reduces right-coronary perfusion pressure and may precipitate right-ventricular ischaemia and failure. Etomidate best preserves vascular tone and cardiovascular reflexes. Thiopental reduces cardiac output and can cause hypotension, but its haemodynamic depression is generally less pronounced than propofol's at equipotent doses. Midazolam may cause dose-dependent hypotension but is usually less abrupt. Ketamine generally increases heart rate and arterial pressure through sympathoadrenal stimulation, although it may increase pulmonary vascular resistance and can reveal direct myocardial depression in catecholamine-depleted patients.

Reference: Grounds RM, Twigley AJ, Carli F, Whitwam JG, Morgan M. The haemodynamic effects of intravenous induction: comparison of the effects of thiopentone and propofol. Anaesthesia. 1985;40:735–740. https://pubmed.ncbi.nlm.nih.gov/3876040/