Plasma Activated Clotting Time as an Indicator of Dangerous Hypocoagulability in Warfarin-treated Trauma Patients: A Preliminary Study

: This study was conducted to determine the possibility of detecting dangerous hypocoagulability in trauma victims given warfarin by measuring plasma activated clotting time (ACT). Sensitivity of the plasma ACT to warfarin was tested using lyophilized plasmas and plasma samples from nontraumatized but anticoagulated patients. Lyophilized plasmas were also used to evaluate the effect of defects in the intrinsic coagulation system on the plasma ACT. The plasma ACT, measured using a 4.4-mM calcium solution, showed satisfactory prolongation when the thrombotest of matched samples was within the therapeutic range for warfarin therapy. Conversely, the plasma ACT was not prolonged when the only abnormality of matched samples was mild to moderate prolongation of the activated partial thromboplastin time (APTT). These findings suggest that the plasma ACT could be a reliable indicator of dangerous hypocoagulability in trauma patients receiving warfarin therapy during the immediate postinjury period.