Haemodynamic effects of oxprenolol and practolol in dogs under halothane anaesthesia.

The effects of beta-adrenergic blockade produced by either oxprenolol or practolol in dogs anaesthetized with nitrous oxide and halothane were studied. The main changes were a fall in cardiac output, heart rate and stroke work index, and an increase in central venous pressure. These changes were more marked with practolol than with oxprenolol but this difference was probably due to a higher degree of beta-adrenergic stimulation during the control period in the dogs receiving practolol. The changes seen could, in the main, be attributed solely to beta-blockade. The possibility that the drugs are also direct myocardial depressants could not be ruled out as in some dogs showing no evidence of beta-stimulation in the control period negative inotropic effects were produced by both drugs.