Influence of aspirin on platelets and the bleeding time.

Aspirin influences the bleeding time, presumably through the inhibition of prostaglandin biosynthesis and the resultant platelet secretion reaction. This can be measured by prolongation of the bleeding time and changes in platelet function results. Despite these changes, bleeding is rarely a problem in patients who have normal hemostatic mechanisms. To investigate this, we have studied the technical variables associated with the determination of the bleeding time. Both venostasis and direction of the incision play a major role in the bleeding time prolongation induced by aspirin. When a bleeding time determination is performed with vertical incision without venostasis, there is almost no detectable prolongation of the bleeding time. These studies support our previous observations that aspirin has a mild influence on primary hemostasis.