Effects of hypothermia on thrombelastography in patients undergoing cardiopulmonary bypass

Thrombelastography (TEG) correlates with postoperative chest drain output in patients undergoing cardiopulmonary bypass (CPB). In vitro incubation with heparinase allows TEG monitoring during CPB, despite heparin anticoagulation. Hypothermia impairs coagulation, but these effects cannot be assessed by standard coagulation tests performed at 37 degrees C. The aim of this study was to assess the effects of hypothermia on TEG. Therefore, we have compared normothermic and temperature-adapted TEG in 30 patients undergoing CPB. Our data showed significantly impaired reaction time (r), kinetic time (k), and angle alpha (alpha) in temperature-adapted compared with normothermic TEG. Maximum amplitude (MA), reflecting absolute clot strength, was not affected at temperatures of 33-37 degrees C. These findings indicate a decrease in the speed of clot formation, but not absolute deterioration in clot quality. Furthermore, heparinase-modified TEG indicated that there were nine cases in which heparin effects persisted after heparin reversal with protamine, providing a rational guide to protamine therapy.