Halothane Cardiac Sensitisation — FRCA Primary MCQ
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Correct answer: C — Halothane
Halothane most strongly sensitises the myocardium to the arrhythmogenic effects of catecholamines, lowering the dose of adrenaline required to produce ventricular ectopy and potentially ventricular tachycardia or fibrillation. This is a characteristic adverse effect of halothane and is especially important when exogenous sympathomimetics are administered or endogenous catecholamine concentrations are increased. Enflurane can also cause myocardial sensitisation, but less than halothane. Isoflurane and sevoflurane have substantially lower arrhythmogenic sensitising effects; the UK isoflurane SmPC explicitly states that sensitivity to adrenaline is lower than with halothane, while sevoflurane has sensitivity similar to isoflurane. Desflurane may cause sympathetic activation when its concentration is increased rapidly, but that is distinct from halothane's pronounced myocardial catecholamine sensitisation.
Reference: Piramal Critical Care Ltd. ISOFLURANE 100% Inhalation Vapour, Liquid, Summary of Product Characteristics, sections 4.5 and 5.1, 2019. https://www.medicines.org.uk/emc/product/9800/smpc