Haemodynamic responses to enflurane anaesthesia and hypovolaemia in the dog, and their modification by propranolol.

The haemodynamic responses to minimum equipotent concentrations of halothane and enflurane were compared in seven dogs. The haemodynamic responses to increasing concentrations of enflurane, and to induced hypovolaemia during enflurane anaesthesia, were studied in the same dogs, both before and after administration of propranolol 0.3 mg kg-1 i.v. In equipotent concentrations, enflurane caused marginally greater impairment of left ventricular function than halothane, and caused a dose-dependent reduction of arterial pressure, cardiac output and myocardial contractility. Following administration of propranolol, these haemodynamic effects of enflurane were marked, and withdrawal of 20% of estimated blood volume was tolerated poorly.