Effect of isoproterenol and propranolol on halothane MAD in dogs.

To evaluate the effect of propranolol on anesthetic requirement, changes in minimum alveolar concentration (MAC) of halothane accompanying acute (2 and 10 mg/kg IV) and chronic (200 mg/day orally for 10 days) propranolol administration were determined in dogs. MAC did not change significantly in either case. Beta-adrenergic blockade was achieved with the 2 mg/kg propranolol dose, as indicated by abolition of the pulse rate increase in response to isoproterenol infusion. Isoproterenol itself did not alter MAC. Mean arterial pressure (MAP) and heart rate (HR) at any given level of alveolar halothane were the same before and after chronic propranolol administration. Acute IV administration of propranolol, especially at the 10 mg/kg dose, reduced MAP and increased HR only transiently.