Comparison of Bedside Coagulation Monitoring Tests with Standard Laboratory Tests in Patients After Cardiac Surgery

We compared portable bedside tests of whole blood coagulation with standard laboratory plasma coagulation tests to assess the accuracy and precision of the bedside tests in a clinical setting (postcardiac surgery). The Ciba Corning 512 Coagulation Monitor (Ciba Corning Diagnostics Corp., Medfield, MA) and the Hemochron 801 (International Technidyne Corp., Edison, NJ) were tested. One hundred forty-one patients who underwent cardiac surgery requiring cardiopulmonary bypass were evaluated upon arrival in the intensive care unit. Nine milliliters of fresh whole blood were used to obtain the prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), and the heparin-neutralized thrombin time (HNTT) that were measured by bedside coagulation monitors. TT and HNTT were only measured by the Hemochron method. Blood from the same sample was also sent to the Hospital Stat Laboratory for simultaneous comparison of bedside results and standard coagulation tests. For PT and aPTT testing, an accuracy of +/- 10% and a precision of +/- 25% were considered clinically acceptable. Both of the PT tests met the dual criteria for clinical acceptability, but the aPTT tests did not meet either criterion. The difference between Hemochron TT and Hemochron HNTT correlated weakly, but significantly, with laboratory aPTT ratio (r = 0.52, P < 0.001). The slope of the regression line indicated that a TT-HNTT difference > 30 s correlated with an aPTT > 1.5 x control. We conclude that, in the postoperative cardiac surgical patient, PT was both accurate and precise in two commercially available tests, but aPTT was not.(ABSTRACT TRUNCATED AT 250 WORDS)