Haemodynamic interactions of high-dose propranolol pretreatment and anaesthesia in the dog. I: Halothane dose-response studies.

The effect of pretreatment for 3 weeks with propranolol 20 mg/kg/day on cardiovascular function during increasing depths of halothane anaesthesia (range 1.0-2.5% inspired halothane with IPPV and normocapnia) were studied in a group of seven closed-chest dogs which had been implanted previously with cardiovascular flow- and pressure-measuring instruments. The results were compared with those observed in a similar group of five untreated dogs. Propranolol pretreatment resulted in a small degree of additional cardiac depression at any inspired halothane concentration. The cardiac depressant effects of propranolol and halothane were found to be simply additive and therefore predictable. The presence of propranolol did not result in morbidity or mortality at any depth of halothane anaesthesia.