During maintenance of anaesthesia with halothane, the surgeon infiltrates lignocaine with adrenaline into the scalp incision. Within a minute the patient develops multifocal ventricular premature beats progressing to brief ventricular tachycardia. The property of halothane responsible for this event is:

• A Inhibition of sinoatrial node automaticity with compensatory ectopy
• B Reflex sympathetic discharge caused by ganglionic blockade
• C Release of endogenous noradrenaline from the adrenal medulla
• D Sensitisation of the myocardium to circulating catecholamines ✓

Explanation

Halothane is the volatile agent that most strongly sensitises the myocardium to exogenous and endogenous catecholamines, permitting triggered activity via delayed afterdepolarisations. This is why halothane is avoided when adrenaline-containing solutions are infiltrated, particularly in children undergoing tonsillectomy or cleft lip repair. The newer ethers, sevoflurane included, carry far less arrhythmogenic risk at equivalent depths of anaesthesia.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.