Platelet Function, Coagulation, and Fibrinolysis Assessed during and after Infrarenal Aortic Surgery.Samama et al.(page 74)

In 17 patients undergoing infrarenal abdominal aortic replacement, Samama et al.  collected blood samples before, during, and after surgery to assess platelet function, coagulation, and fibrinolytic status. All patients were given a bolus of 50 IU/kg unfractionated heparin intravenously immediately before aortic cross-clamping. In addition, daily subcutaneous injections of 3,075 Anti Xa IU of low-molecular-weight heparin were given during the postoperative period as prophylaxis against deep vein thrombosis.

Measured blood loss, fluid loading, and transfusion requirements during surgery were recorded. Blood samples were taken before induction of anesthesia, 1 h after incision, 1 h after extubation in the recovery room, 24 and 48 h postoperatively, and at postoperative day 7. Aggregometry and flow cytometry studies, prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, thrombin–antithrombin complexes, plasminogen activator inhibitor 1, platelet count, and hematocrit determination analyses were performed after surgery. A significant increase in adenosine diphosphate–induced platelet aggregation was observed in blood samples collected 24 and 48 h postoperatively but was not associated with a change in flow cytometry profile. A higher fibrinogen rate was detected on days 2 and 7 after surgery. Platelet counts increased significantly later—in samples collected on day 7 after surgery. No increase in thrombin–antithrombin was recorded at any time. Significant but temporary inhibition of fibrinolysis was observed 1 h after extubation and 24 h postoperatively. The activation of platelets evidenced during the early postoperative period, associated with an increased fibrinogen rate and temporary shut down of fibrinolysis, indicates increased thrombotic risk for patients undergoing major vascular surgery. Therefore, evaluation of benefit/risk ratios of antiplatelet and anticoagulant agents in this setting may be warranted.