Oxprenolol and the circulation during anaesthesia in the dog: influence of intrinsic sympathomimetic activity.

Oxprenolol is a non-selective adrenergic beta-receptor antagonist displaying beta-mimetic activity. To test the hypothesis that beta-mimetic activity could minimize the response of the circulation to adrenergic beta-receptor blockade, cumulative dose-response curves to oxprenolol 0.1-1.6 mg kg-1 were obtained in seven anaesthetized dogs. Anaesthesia was maintained with 0.5% halothane supplementing nitrous oxide 66% in oxygen, under moderately hypocapnic IPPV. Oxprenolol, up to 0.4 mg kg-1 i.v., caused modest increases in heart rate, LV dP/dt max and cardiac output. With the largest dose (1.6 mg kg-1), significant increases in heart rate (+19%), LV dP/dt max (+13%) and cardiac output (+27%) were observed while arterial pressure remained unchanged and systemic vascular resistance decreased (-18%).