[Haemodynamic changes during intracoronary infusion of norepinephrine. A study of the halothane-induced circulatory...

The haemodynamic effects of halothane (0.9 vol% = 1 MAC) and of intracoronary infusion of norepinephrine (14.28 +/- 3.28 ng/kg/min) were investigated in anesthetized dogs (n=6). During inhalation of halothane the left ventricular (LV) stroke volume was diminished while heart rate and total peripheral resistance exhibited no significant changes. In spite of this cardiodepressive action, by means of a decrease in both LV-end-diastolic pressure and LV-end-diastolic volume, a backward heart failure could be excluded. Intracoronary infusion of norepinephrine increased the contractility of the left ventricle leading to an increase in LV-dP/dtmax to control values. However, in comparison to the original level, cardiac output and mean arterial blood pressure remained decreased. Thus, selective inotropic stimulation failed to antagonize the halothane-induced circulatory depression. In a second series of experiments performed on chronically instrumented dogs (n=5) the haemodynamic effects of piritramide (0.3 mg/kg/h i.v.), i.e. the anaesthetic used for preparation of the animals in the acute experiments, were studied during anaesthesia with halothane (1 MAC). While dipidolor failed to elicit significant changes under these conditions, haemodynamic side effects cannot generally be excluded since there is evidence that narcotic analgesics interfere with the neural control of the cardiovascular system.