Impact of Graded Hypothermia on Coagulation and Fibrinolysis

BackgroundHypothermia has a detrimental effect on hemostatic mechanism. The purpose of this experimental study was to investigate the effect of graded hypothermia on markers of the anticoagulant system (antithrombin III and protein C) and fibrinolytic system (plasminogen, α2-antiplasmin), and on vascular wall and other tissue specimens.Materials and methodsTen New Zealand rabbits were subjected to mild and then moderate core hypothermia of 32°C for 60 min. Blood samples were obtained at normothermic (T1), mild (T2), and moderate (T3) hypothermic conditions. Chromogenic assay methods were used to determine quantitatively (%) the activity of antithrombin III, protein C, plasminogen, and α2-antiplasmin. Hypothermic values were compared with the normothermic values. Tissue and vessel wall specimens were examined under light microscope.ResultsReduction of activity (%) from normothermia (T1) to mild (T2) and moderate (T3) hypothermia was found for antithrombin III (103.40 ± 12.54, 87.40 ± 13.50, and 82.70 ± 20.78, respectively, with statistically significant difference between T1–T3: P=0.03), for protein C (70.1 ± 7.51, 56.30 ± 8.34, and 53.1 ± 7.34, with statistically significant difference between T1–T2 and T1–T3: P=0.015 for both comparisons) and α2-antiplasmin (97 ± 9.63, 80.60 ± 11.73, and 83.70 ± 13.94, with statistically significant difference between T1–T2: P=0.006). Plasminogen activity was increased (14.50 ± 0.52, 16.30 ± 1.63, and 17.30 ± 2.45, with statistically significant difference between T1–T2 and T1–T3: P=0.033 for both comparisons). Histologic examination revealed no significant lesions on tissue and vessel wall specimens.ConclusionsThe results of our study suggest that even though the hypothermia period was relatively short, the processes of coagulation and fibrinolysis were altered with simultaneous changes.