Interrelationships between platelets and coagulation in the pathogenesis of venous thrombosis.

The relationship between platelets and coagulation in the pathogenesis of venous thrombosis is reviewed. Platelet coagulant activities, coagulation factors and platelet numbers were measured pre- and postoperatively in patients who underwent hip surgery. About 50% of patients developed venous thrombosis. No significant pre-operative differences were observed in platelet coagulant activities between the group of patients who developed thrombosis and the group who did not. However, platelet counts and coagulation activities were significantly higher postoperatively in patients with thrombosis. The postoperative increase in platelet activity preceded venographically observable thrombosis. The author concludes that in patients with thrombosis there may be an increase of young platelets which are 'hyperactive' and which may trigger thrombosis in areas of stasis. It is not impossible that the increased platelet coagulation activity was the result rather than the cause of thrombosis. However, the temporal sequence of effects observed militate against this possibility.