Haemodynamic effects of isoflurane during propofol anaesthesia

We have studied haemodynamic responses to 0, 0.25, 0.5, 0.75 and 1 MAC isoflurane administration in 10 patients during a zero-order propofol infusion and normocapnia. Isoflurane reduced mean arterial pressure (MAP), systemic vascular resistance and left ventricular stroke work in a dose-dependent manner (29%, 38% and 33%, respectively, at 1 MAC), while cardiac output (CO), stroke volume (SV) and heart rate were not affected significantly. Mean pulmonary artery pressure, pulmonary vascular resistance and right ventricular stroke work decreased by 13%, 10% and 17%, respectively (not significant). Pulmonary capillary wedge pressure and central venous pressure were affected minimally, while intrapulmonary shunting and PaO2 remained constant. It is concluded that administration of isoflurane during infusion of propofol caused a dose-dependent decrease in MAP as a result of afterload reduction without modification in CO or SV.