Epidural anesthesia prevents hypercoagulation in patients undergoing major orthopedic surgery

Epidural anesthesia (EA) is known to reduce postoperative thromboembolic complications, but mechanisms are incompletely understood. In this study, we tested the hypothesis that local anesthetics (LA) prevent postoperative hypercoagulability without affecting physiologic aggregation and coagulation processes. Clot signature analysis (CSA) was used to assess platelet and clotting function. Venous blood samples were collected pre- and postoperatively from 41 patients undergoing major orthopedic surgery. The effect of surgery on 3 CSA parameters (platelet-mediated hemostasis time [PHT], clotting time [CT], and collagen-induced thrombus formation [CITF]) was determined in patients receiving EA (n = 20) and those receiving general anesthesia (GA) (n = 21). In the GA group, orthopedic surgery induced a hypercoagulable state: PHT was reduced by 39% +/- 8.6% (P <.001), CT by 21% +/- 3.3% (P <.001), CITF by 10.3% +/- 5.9% (P =.06) compared with respective baseline values. In the EA group, by contrast, no parameter was altered significantly, but PHT showed a tendency towards prolongation by 33.2% +/- 15.4% (P =.25). CT changed by 0% +/- 4.4% (P =.89), CITF by 3.8% +/- 7% (P =.78). Use of EA prevents immediate postoperative hypercoagulability without affecting physiologic aggregation and coagulation processes. Also, CSA appears useful in predicting hypercoagulability and detecting platelet dysfunction. Reg Anesth Pain Med 2001;26:215-222