Hypothermia-induced Haemostatic and Biochemical Phenomena. An Experimental Model.

Hypothermia (24°C) was induced in 7 healthy male dogs. Hematological, hemostatic and biochemical parameters were evaluated before the onset and after 3 h of hypothermia. Following hypothermia, there was a significant increase in red cell count, hematocrit and haemoglobin concentration. The white cell and platelet counts were decreased significantly and the mean platelet volume increased significantly. The activated partial thromboplastin time was significantly prolonged whereas the prothrombin time was unchanged. Associated with these changes there was a significant increase in serum glucose and a small increase in aspartate transaminase activity probably due to muscle leakage. No change occurred in the more liver-specific alanine transaminase. The arterial pH decreased and the changes in gasses observed as a result of hypothermia were compatible with a mixed respiratory-metabolic acidosis. The mean aortic blood pressure also dropped markedly. The hematological and hemostatic changes suggest that widespread tissue 'injury' occurs even in short term hypothermia with platelet activation and accumulation in the liver and spleen. This model of hypothermia may be of use in the study of the thrombotic diathesis observed in this condition and serve as a test bed for drugs of potential use in conditions such as Raynaud's syndrome and hypothermic surgery (e.g. coronary artery bypass).