Failure of General Anesthesia to Potentiate Propranolol Activity

Publisher Website
Google Scholar
Abstract
To determine whether halothane and morphine, commonly used during anesthesia for cardiac operations, potentiate the .beta.-blocking activity of propanolol, hemodynamic changes induced by 5 incremental doses of propranolol (10, 20, 50, 120, 200 .mu.g/kg) were measured in dogs, during halothane, 1%, in O2 and morphine, 4 mg/kg administration. Against a background of constant .beta.-stimulation by infusion of isoproterenol, 0.1 .mu.g/kg per min and vagal blockade by atropine, 3 mg, propranolol produced significant dose-related decreases in heart rate, cardiac index, stroke volume index and left ventricular dP/dtmax [derivative of pressure/derivative of maximum time] and significant increases in mean aortic pressure, systemic vascular resistance and pulmonary capillary wedge pressure. Compared with basal anesthesia with pentobarbital, 15 mg/kg, neither morphine nor halothane increased sensitivity to any measured effect of propranolol expressed as the slope of the log dose-response relationship. The .beta.-blocking activity of propranolol is not potentiated by morpine and halothane anesthesia but rather, their effects are additive.