DETERMINATION OF NORMAL VERSUS ABNORMAL ACTIVATED PARTIAL THROMBOPLASTIN TIME AND PROTHROMBIN TIME AFTER CARDIOPULMONARY BYPASS

Objective: The study's objective was to determine the prothrombin time (PT) and activated partial thromboplastin time (aPTT) values that dif ferentiated normal from excessively bleeding patients immediately afte r cardiopulmonary bypass(CPB). Design: A prospective blinded study. Se tting: A large academic medical center. Participants: 148 patients wer e studied. Interventions: aPTT and PT were determined by the hospital laboratory and the Biotrack 512 Coagulation Monitor (Ciba Coming Diagn ostics, Medfieid, MA) from an arterial whole blood sample obtained 10 minutes after protamine administration. Patients were subjectively and objectively defined as ''bleeders'' or ''nonbleeders'' with blinded o bservers. Measurements and Main Results: The specificity and sensitivi ty were determined by a receiver operating characteristic (ROC) analys is. Twenty-three of 148 patients (14.9%) were characterized as bleeder s. The laboratory PT had a maximal specificity and sensitivity of 78% and 75%, respectively, at a value of 15.4 s, with a negative and posit ive predictive value of 93% and 33%, respectively. The maximal specifi city and sensitivity of the laboratory aPTT was 64% and 76%, respectiv ely, at a value of 46 s, with a negative and positive predictive Value of 89% and 33%, respectively. aPTT and PT approached normal values af ter 12 hours in the intensive care unit. Conclusion: The aPTT and PT v alues that produce the maximal sensitivity and specificity in the ROC analysis may be helpful to differentiate patients who are bleeding exc essively from those patients who are not after CPB and to guide transf usion of blood products. New whole blood coagulation devices with rapi d turn around times had similar predictive value for bleeding tendency compared with standardized laboratory tests. Copyright (C) 1995 by W. B. Saunders Company