SHEAR-INDUCED PATHWAY OF PLATELET-FUNCTION IN CARDIAC-SURGERY

The contribution of platelet dysfunction to the impaired hemostasis af ter cardiac surgery remains to be established, because there is no sen sitive method to assess platelet function. Measurement of the shear-in duced pathway of platelet function, an important mechanism in inducing hemostasis, became possible by a novel shear-inducing technique, the in-vitro bleeding test (Thrombostat 4000). By using this test, the cha nges in platelet function during cardiopulmonary bypass and their cont ribution to hemostasis were investigated in patients undergoing cardia c surgery. Platelet function is quickly impaired shortly after the sta rt of cardiopulmonary bypass, and partly recovered at the end of cardi opulmonary bypass. The function of aspirin-treated platelets is more s everely affected than of nonaspirin platelets during cardiopulmonary b ypass. Furthermore, the degree of platelet dysfunction at the end of t he operation, but neither the platelet number nor the activated clotti ng time, was significantly correlated with blood loss from the chest d rain after cardiac surgery. These results indicate the significant and variable effects of cardiopulmonary bypass on the shear-induced pathw ay of platelet function. Moreover, the impairment of this function of platelets appears to be a major cause of excessive bleeding in patient s after cardiac surgery. Therefore, the routine use of the shear-induc ing test seems helpful to make a proper diagnosis and design the thera py for bleeders after cardiac surgery.