BRADYCARDIA AND HYPOTENSION DURING CYCLOPROPANE ANAESTHESIA CAUSED BY HYOSCINE AS PREMEDICATION

In a series of 613 patients, most of whom were undergoing abdominaloperations under anaesthesia with cyclopropane and tubocurarine,the incidence of fall in pulse rate and arterial pressure was38 per cent following morphine-hyoscine premedication, 20 percent with morphine as premedication and 10 per cent when morphine-hyoscinewas supplemented with atropine 0.6 mg intravenously. Electrocardiographictracings revealed a high incidence of arrhythmia, includingtwo instances of multifocal ventricular extrasystoles, whenatropine was administered during cyclopropane anaesthesia. Itis concluded that hyoscine is the cause of these changes dueto its central vagal stimulating effect. Atropine injectionduring cyclopropane anaesthesia appears to lead to a high incidenceof arrhythmia, with a risk of ventricular fibrillation and shouldbe avoided. It is advised that atropine be given intravenously(0.6 mg in adults) before induction of anaesthesia with cyclopropanewhen hyoscine has been used for premedication.