Hypothermic cardiopulmonary bypass (CPB) has been associated with both coagulation defects and hemorrhage. The influence of temperature on platelet function and the benefits of aprotinin in this situation were studied in 60 patients undergoing elective aortocoronary bypass grafting. The patients were randomly divided into four groups (15 patients per group): group 1, normothermic CPB (nasopharyngeal temperature > 34-degrees-C); group 2, normothermic bypass and administration of high-dose aprotinin (2 million IU before CPB, 500,000 IU/h until the end of the operation, and 2 million IU added to the prime); group 3, hypothermic CPB (nasopharyngeal temperature < 28-degrees-C); and group 4, hypothermic CPB and aprotinin. Platelet function was evaluated by aggregometry (turbidimetric technique), and aggregation was induced by adenosine diphosphate (1 and 2 mumol/L), collagen (4 mug/L), and epinephrine (25 mumol/L) before, during, and after CPB into the first postoperative day. Starting from comparable baseline values, maximum platelet aggregation and maximum gradient of platelet aggregation were significantly most reduced after CPB in group 3 (hypothermic CPB without aprotinin) (ranging from -30% to -53% relative to baseline values). In comparison with the other groups, platelet function in this group also recovered less quickly in the later post-bypass period. Hypothermic CPB with aprotinin resulted in less-altered platelet function than hypothermic CPB without aprotinin. Platelet aggregation in aprotinin-treated patients was comparable overall with that in patients undergoing normothermic CPB. On the first postoperative day, aggregation variables had returned to or exceeded baseline values. Blood loss on the first postoperative day was significantly higher in group 3 (680 +/- 220 mL) than in the other groups, and need for homologous blood and fresh frozen plasma was also most pronounced in these patients (6 units of packed red cells and 4 units of fresh frozen plasma). We conclude that aprotinin blunted the negative effects of hypothermic CPB on platelet function but failed to have any beneficial effects in patients undergoing normothermic CPB.
