The influence of aspirin on postoperative platelet kinetics and venous thrombosis.

Several parameters of platelet kinetics were followed in 105 middle-aged and elderly postoperative patients, half of whom were randomly allocated to receive aspirin. A significantly lower incidence of venous thrombosis, as detected by 125I-fibrinogen scanning, was found among patients receiving aspirin when compared with the control group. Platelet survival was shortened in the postoperative state, an effect that was inhibited by aspirin. The development of deep vein thrombosis did not shorten platelet survival, nor did fibrinogen survival discriminate patients with venous thrombosis. Treatment with aspirin reduced urinary excretion of 5-hydroxy indole acetic acid--presumably by inhibiting in vivo platelet release of serotonin, reduced postoperative consumption of platelets, and reduced the mean corpuscular volume of the platelet population. These studies suggest that platelet function is important in the pathogenesis of postoperative venous thrombosis.