Effect of hypothermia on the coagulation cascade

The series of enzymatic reactions of the coagulation cascade are strongly inhibited by hypothermia, as demonstrated by the dramatic prolongation of prothrombin time and partial thromboplastin time tests at hypothermic deviations from normal temperature in a situation where factor levels were all known to be normal. Clinicians who deal with critically ill massively transfused hypothermic patients all recognize the inevitable appearance of a coagulopathy that has a multifactorial origin. Unless specifically considered, the contribution of hypothermia to the hemorrhagic diathesis may be overlooked since coagulation testing is performed at 37 degrees C, rather than at the patient's actual in vivo temperature.