Circulatory adaptation after aortic valve replacement. A clinical study peroperatively and in the early postoperative period.

The myocardial function and the central and peripheral circulation were studied after aortic valve replacement. All patients showed a similar postoperative pattern of response. During the operation, after termination of bypass, the mean arterial blood pressure (Pa,m) was low. The total peripheral vascular resistance (TPR) and pulmonary vascular resistance (PVR) were normal. Immediately after the operation Pa,m, TPR and PVR were higher than peroperatively. The cardiac index (CI) and stroke index (SI) were low, and the heart rate (HR) was high. At this stage the oesophageal temperature was increasing, but there was no shivering. Then followed a period in which Pa,m and TPR decreased, while CI and SI remained essentially unchanged. The oesophageal temperature reached its highest value 5 hours postoperatively. Peripheral warming began in the 3rd hour postoperatively and was completed in the 6th hour, when the peripheral temperature was 35 degrees C. The progressive peripheral warming, with peripheral cutaneous vasodilatation and slight reduction of the heart rate, took place without signs of increasing CI or SI. The left and right ventricular function, expressed as the relation between LVSWI and Pla,m, and RVSWI and Pra,m, respectively, varied postoperatively and showed no signs of improvement at the time of peripheral warming. Cardiac output and myocardial function seemed to be little affected by the obvious changes appearing during the systemic and peripheral vasodilatation in connection with central and peripheral warming.