INFLUENCE OF DIFFERENT INTRAVASCULAR VOLUME THERAPIES ON PLATELET-FUNCTION IN PATIENTS UNDERGOING CARDIOPULMONARY BYPASS

The influence of four different kinds of intravascular volume replacem ent on platelet function was investigated in 60 patients undergoing el ective aortocoronary bypass grafting using cardiopulmonary bypass (CPB ). In a randomized sequence, high-molecular weight hydroxyethyl starch solution (HMW-HES, mean molecular weight [Mw] 450,000 d), low-molecul ar weight HES (LMW-HES, Mw 200,000 d), 3.5% gelatin or 5% albumin were infused preoperatively to double reduced filling pressure (pulmonary capillary wedge pressure [PCWP] < 5 mm Hg). Fifteen untreated patients served as a control. Platelet function was assessed by aggregometry u sing turbidometric technique (inductors: ADP, epinephrine, collagen). Maximum aggregation, maximum gradient of aggregation, and platelet vol ume were measured before, during, and after CPB until the first postop erative day. HMW-HES 840 +/- 90 mL, LMW 850 +/- 100 mL, gelatin 950 +/ - 110 mL, and albumin 810 +/- 100 mL were given preoperatively. Maximu m platelet aggregation (ranging from -23% to -44% relative from baseli ne value) and maximum gradient of platelet aggregation (ranging from - 26% to -45% relative from baseline values) were reduced only in the HM W-HES patients. After CPB, aggregometry also was impaired most markedl y in these patients. The other volume groups showed less reduction in platelet aggregation and were similar to the untreated control. On the first postoperative day, aggregation variables had returned almost to baseline in all patients. Platelet volume was the same among the grou ps within the investigation period. Postbypass blood loss was highest in the HMW-HES group (890 +/- 180 mL). There was significant (P < 0.04 ) correlation in this group between blood loss and change in platelet aggregation. The need for homologous blood was comparable among all gr oups. It is concluded that volume replacement with HMW-HES resulted in the most pronounced impairment of platelet aggregation associated wit h the highest postoperative blood loss. Thus HMW-HES should be avoided particularly in patients at risk of enhanced and prolonged postoperat ive bleeding, whereas the other solutions were similar with regard to platelet function.