Effect of propranolol on cardiac arrhythmias induced by adrenaline under halothane anesthesia.

Abstract

The antagonizing effect of propranolol (Inderal®) on the arrhythmias induced by exogenous adrenaline under halothane anesthesia was investigated in dogs as well as in patients. The results obtained were summarized as follows. 1. Propranolol in a dose of 100 γ/kg given intravenously completely antagonized the stimulating effect of adrenaline on the heart in dogs. The half life of the action was found to be 45-50 minutes. 2. Propranolol in a dose of 50 γ/kg given intravenously decreased the adrenaline sensitivity of the heart under halothane anesthesia almost to that under thiopental anesthesia in dogs. 3. Propranolol in a dose of 100 γ/kg given intravenously under halothane anesthesia in dogs reduced cardiac output and pulse rate by approximately 22% and 14%, respectively, but did not show any significant effect on blood pressure. 4. When patients were administered 50 γ/kg of propranolol previously, the incidence of cardiac arrhythmias induced by the intramuscular infiltration of 50 γ/kg of adrenaline under halothane anesthesia was found less than that under ether anesthesia. The arrhythmias encountered were converted to normal sinus rhythm by the administration of 50 γ/kg of propranolol in every case. In view of the results obtained, propranolol seems to be useful in preventing the adrenaline-induced cardiac arrhythmias, and it may be suggested that a prior intravenous administration of 50 γ/kg of propranolol makes adrenaline available in commonly used doses even under halothane anesthesia. The authors wish to thank Sumitomo Chemical Co. Ltd. (Japan) which made available the propranolol (Inderal®) in this study.