PREDICTIVE VALUE OF BLOOD-CLOTTING TESTS IN CARDIAC SURGICAL PATIENTS

This study prospectively evaluated numerous tests of clotting function in 897 consecutive adult cardiac surgical patients over 18 months. Th is included coronary operation, valve replacement, and reoperative pat ients. The tests included activated clotting time, activated partial t hromboplastin time, prothrombin time, thrombin time, fibrinogen, fibri n/fibrinogen degradation products, platelet count, and Duke's earlobe bleeding time. Other variables such as age, sex, and cardiopulmonary b ypass duration were included in the multivariate analysis. Statistical ly significant correlations were found between 16-hour mediastinal dra inage and activated partial thromboplastin time, fibrinogen, activated clotting time, fibrin/fibrinogen degradation products, platelet count , and prothrombin time. Scatter plots indicate that these relationship s, although statistically significant, had little predictive value and were largely significant as a result of the large number of patients in each group, which permitted weak correlations to reach statistical significance. The best multivariate model constructed could explain on ly 12% of the observed variation in postoperative blood loss. Because the predictive values of the tests are so low, it does not appear sens ible to screen patients routinely using these clotting tests shortly a fter cardiopulmonary bypass.