In hypothermic patients, a tendency to bleed may be observed even when hemostatic tests seem to be normal. Coagulation and platelet function tests are usually performed at 37 degrees C. We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function testing using Sonoclot Analyzer (Sonoclot) and Thromboelastography (TEG). Anesthesia was induced and maintained with IV ketamine and fentanyl on 15 male New-Zealand White rabbits. A water blanket was used to induce hypothermia to 30 degrees C and to rewarm to 37 degrees C. Blood samples were obtained at four points: before hypothermia, at 34 degrees C, at 30 degrees C, and after rewarming. Standard coagulation tests were performed at 37 degrees C (C method), and simultaneously, real temperature hemostasis function tests (R method) were run. In Sonoclot(R), activated clotting time and time to peak increased and clot rate decreased significantly at 30 degrees C in the R method compared with those in the C method. In TEG(R), reaction time and clot formation time were prolonged and clot formation rate was diminished at 30 degrees C in the R method compared with those in the C method. Induced hypothermia delayed the coagulation cascade and reduced platelet function. During hypothermia, hemostatic measurements should be performed at real temperature to avoid overestimating patient hemostatic function based on results measured at the standard 37 degrees C.
Implications: We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function tests in rabbits using Sonoclot Analyzer and Thromboelastography. Induced hypothermia delayed the coagulation cascade and reduced platelet function. The conventional coagulation tests performed at 37 degrees C failed to detect these hypothermia-induced degradations in hemostasis performance.