Postoperative alterations in platelet function induced by cardiopulmonary bypass (CPB) are of importance. The effect on platelet aggregation of three different techniques for reducing blood consumption was studied in 30 patients undergoing elective aortocoronary bypass grafting from the beginning of anesthesia until the 1st postoperative day. The patients were randomly divided into three groups, in which 1) a cell separator was used during and after CPB; 2) a hemofiltration device was used; and 3) high-dose aprotinin was used in order to reduce the need of homologous blood. A fourth group undergoing neurosurgery procedures served as a control. Platelet aggregation induced by adenosine diphosphate (concentration 0.25, 0.50, 1.0, and 2.0-mu-M), collagen (4-mu-l/ml), and epinephrine (25-mu-M) was determined by the turbidimetric method. Platelet aggregation was not significantly changed in the control group, indicating that the operation itself did not impair platelet function. At the end of the operation (after retransfusion of the salvaged pump blood), the maximum aggregation and maximum gradient of aggregation induced by all three inductors were most reduced (significantly) in the cell-separator patients. On the 1st postoperative day, platelet aggregation in the hemofiltration patients and the patients treated with aprotinin had normalized. Aggregation of patients pretreated with high-dose aprotinin was not different from that of the hemofiltration patients throughout the investigation. Blood loss was significantly highest in the cell-separator group (770 +/- 400 ml on the 1st postoperative day) but was not different between the hemofiltration (390 +/- 230 ml) and the aprotinin-treated patients (260 +/- 160 ml). It can be concluded that the use of the cell separator resulted in the most pronounced deterioration in platelet aggregation. Compared to the use of a hemofiltration device, high-dose aprotinin had no positive effects either on platelet aggregation variables or on blood loss and cannot be recommended in elective, uncomplicated aortocoronary bypass operations.