Changes in the rheologic properties of blood after a high altitude expedition.

The changes in blood rheologic properties induced by exposure to high altitude plus heavy and prolonged physical strain were investigated in 14 climbers of an Italian expedition to Himalaya (maximum altitude reached m 7350). In blood samples collected immediately after return, alterations of some haemorheologic parameters were observed in comparison with baseline values, and namely an increase in relative blood viscosity, fibrinogen and erythrocyte filtration time along with a fall in platelet count. Treatment with a drug acting on the red cell deformability (Pentoxifylline) appeared to prevent the changes in blood viscosity and erythrocyte filterability. In the 9 climbers whom we were able to re-examine after three months, all altered parameters were found to be restored to baseline values. These results contribute to the knowledge of the pathogenesis of high altitude disease and stress the significance of altered haemorheology as one of the mechanisms possibly involved in the vascular events observed in this condition.