Haemostasis at high altitude

Abstract

Haemostasis has been studied by several authors during exposure to altitude hypoxia. On acute induction to hypoxia, platelet count, platelet aggregability and bleeding time are normal; an increase of thromboxane released from platelets and of prostacyclin, released from endothelial cells is observed; coagulation factors are unchanged except of F. VIII which is increased; modified antithrombin III (ATm) are normal; fibrinopeptide A is increased in subjects with pulmonary edema and fibrinolytic activity after venous occlusion is normal. In chronic hypoxia, during a stay at 6542 m (Mt. Sajama), we found in 7 subjects an important increase in D. Dimer (p < 0.001) that seems to correspond to an activation of coagulation and a decrease of F. VIII R. Cof/F. VIII R. Ag ratio which suggests an endothelial cell damage.