Delayed hemostatic changes following cardiopulmonary bypass

Abstract

A variety of hemostatic abnormalities has been reported in patients following open-heart surgery. Since surgery itself may induce changes in the coagulation system, the analyses of postoperative coagulation assays in the bleeding patients may be extremely difficult to interpret without an understanding of the coagulation dynamics in the nonhemorrhagic postoperative patients. Thus, we studied the pattern of change in several coagulation assays performed on 36 consecutive patients before and during the first two postoperative weeks. Approximately one third of the patients has some clotting abnormality before surgery. Shortened prothrombin time (PT) and activated partial thromboplastin time (APTT) were observed within the first three postoperative days. Only following warfarin therapy (initiated on the third postoperative day) was significant prolongation of PT and APTT observed. During the 14 postoperative days, fibrinogen levels and fibrinogen degradation products progressively increased without prolongation of the thrombin time or decrease in the euglobulin clot lysis time. On the first postoperative day, the platelet count and platelet adhesiveness values were significantly less than before surgery (p less than 0.01 and p less than 0.05). Over the following two weeks, the platelet count and platelet adhesiveness returned to normal. Although there was slight lengthening of the Ivy bleeding time on the first postoperative day, this assay was never abnormal. Thus, we conclude that the following cardiopulmonary bypass there is (1) probably activation of circulating procoagulants, (2) progressive increase in fibrinogen levels, (3) activation to the fibrinolytic system, and (4) transient thrombocytopenia with a superimposed platelet defect.