Hypothermia and hyperthermia decrease the anticoagulant potency of low molecular weight heparin measured with thrombelastgraphy

Abstract

BACKGROUND: It is a fact that anticoagulant potency of low molecular weight heparin (LMWH) is well established under normothermic conditions. The aim of our study was to evaluate the effect of hypo- and hyperthermia on LMWH anticoagulation as measured by thrombelastography. METHODS: Blood from 10 healthy volunteers was investigated before and after subcutaneous administration of 5000 IE of LMWH (dalteparin). Thrombelastography was performed with recalcified citrated whole blood with and without heparinase incubation at different test temperatures. RESULTS: Mean ± SD reaction time was within the normal range before LMWH administration (18 ± 5.4 mm at 37° C). LMWH prolonged reaction time to 35 mm at 37° C, but non-normothermic test temperatures significantly decreased reaction time to 28 mm at 33° C, to 33 mm at 35° C, to 21 mm at 38° C, and to 20 mm at 41° C. Similarly, clot formation time was decreased from 24 mm at 37° C to 19 mm at 33° C, to 22 mm at 35° C, to 21 mm at 38° C, and to 20 mm at 41° C (P < 0.05). CONCLUSIONS: These results show that both hypo- and hyperthermic conditions significantly decreased the anticoagulant potency of LMWH when assessed by TEG® analysis. These findings may be of clinical relevance in non-normothermic patients.