Effect of propranolol on arterial hypotension induced by halothane in the dog under nitrous oxide anaesthesia

Abstract

The effect of propranolol hydrochloride on arterial hypotension produced by halothane has been investigated in atropinized dogs during nitrous oxide-oxygen anaesthesia. Propranolol alone produced a slight transient fall in blood pressure, but greatly enhanced the hypotensive action of halothane. Following the application of electric shock to the heart to terminate adrenaline-induced ventricular fibrillation during halothane-nitrous oxide anaesthesia, propranolol produced a profound fall in arterial pressure. A shock-like state associated with marked bradycardia resulted. Therapy with adrenaline and mephentermine produced slow recovery, and the pressor response was not associated with any increase in heart rate. The outcome of pressor therapy was related to the number of electric shocks applied to the heart. Two dogs in which electric shock was applied thrice failed to recover in spite of vigorous pressor therapy. It is suggested that caution should be exercised when injecting propranolol during halothane anaesthesia in humans. The use of this drug following the application of electric shock to the heart to terminate ventricular fibrillation may be hazardous and should be avoided. © 1967 John Sherratt and Son Ltd.