Near-patient testing for coagulopathy after cardiac surgery

We assessed the accuracy and precision of a new near-patient testing system (Hemochron Response) by measuring prothrombin time and activated partial thromboplastin time (PT and APTT) in 50 patients undergoing cardiac surgery using cardiopulmonary bypass and comparing the results with laboratory assays.

Blood samples were taken at the beginning of surgery and the PT and APTT was measured both in the laboratory and by the Hemochron Response. The tests were repeated 30 min after reversal of heparin with protamine.

Before bypass, the bias for PT was only +0.34, with small 95% limits of agreement. Making the same measurements after bypass, the Hemochron Response under-read and the bias was -3.27, with an increase of the 95% limits of agreement. With the APTT, the bias and the 95% limits of agreement were greater before bypass, and became even wider after bypass.

We found good agreement in the PT and clinically acceptable levels of agreement in the APTT during the pre-bypass period. After bypass, bias became greater for both PT and APTT and the limits of agreement could be clinically unacceptable.