Pro-coagulant effect of in vitro haemodilution is not inhibited by aspirin.

We have conducted an in vitro coagulation study, using the thrombelastograph (TEG), to determine if the enhanced coagulability of whole blood after haemodilution with normal saline can still be demonstrated after administration of an antiplatelet agent. Aspirin inhibits the platelet-endothelial interaction that is part of the coagulation process. We investigated the role of aspirin in the phenomenon of haemodilution-induced coagulability to identify if the platelet-endothelial system is involved in the process. Previous work showed that the TEG is not altered by oral ingestion of aspirin. Blood from 20 volunteers was divided into two aliquots of 4 ml each. One sample was diluted by 20% by addition of 0.9% saline 1 ml while the other was not diluted and served as a control. Coagulation studies were performed using the TEG and enhanced coagulation was seen in the saline diluted samples. Subjects then received soluble aspirin 375 mg daily for 3 days, after which the tests were repeated. There was no difference in the control TEG values and saline enhancement of coagulation was preserved in all subjects after 3 days of aspirin administration. We conclude that aspirin had no effect on the observation that haemodilution with saline enhances the coagulability of whole blood.