Global hemostatic tests, protein C and anti-thrombin in the intensive care unit setting; correlations and ability to predict outcome

Abstract number: P0575

Nilsson^* G., Astermark† J., Vernersson‡ E., Berntorp† E.

^*Department of Anaesthesiology, Sweden; ‡Department of Anaesthesiology, University Hospital, Malmö, Sweden †Department of Coagulation Disorders, Sweden;

Coagulation tests are often abnormal in critically ill patients. We have shown the usefulness of the global hemostatic tests INR (International Normalized Ratio) and APTT (Activated Partial Thromboplastin Time) to predict survival in critically ill patients. Prolonged APTT, especially, was associated with a poor prognosis. The possibility to analyze the inhibitors protein C and anti-thrombin are limited to a smaller number of laboratories and are often available only during office hours, which may jeopardize the optimal use of coagulation inhibitor concentrates. We therefore studied the usefulness of global hemostatic tests to predict the levels of protein C and anti-thrombin and the outcome of patients. Blood samples were collected from patients within 6 h of admission to an intensive care unit (ICU) and tested regarding platelet count, INR, and APTT. If platelet count was <100 × 10⁹ L^-1 , INR > 1.36 and/or APTT > 45 s, we continued with a second sampling within 6 h after the first one for analysis regarding protein C and anti-thrombin. Ninety-two patients were included; the length of the stay at the ICU and hospital, the survival time at leaving the ICU and hospital and after 30 and 180 days were recorded. Using univariate analysis of variance, APTT and INR could predict separately the levels of the two inhibitors. Neither platelet count nor any combinations of the global hemostatic tests were predictive. The survival predicting ability expressed as odds ratios (the cut-offs calculated by 80% survival) indicated that decreased protein C, but not anti-thrombin, predict a lower survival rate at studied time-points. Thus, a protein C level <0.39 IU mL^-1 gives an odds ratio for survival at, e.g. 30 days of 0.18 (0.063–0.53). We conclude that the global hemostatic tests INR and APTT can predict the levels of protein C and, though less so, of anti-thrombin. This may be useful information in giving replacement therapy when the possibility of rapid analysis of coagulation inhibitors is limited. Especially prolonged APTT and/or low protein C level indicate a sinister prognosis in the ICU patient.