Ultrasound Surveillance to Detect Postoperative Venous Thrombosis

To the Editor. —I appreciate the tremendous effort of Francis et al1in comparing warfarin and external pneumatic compression for prevention of venous thrombosis after total hip replacement. I wonder, however, why they did not explore the effect of intraoperative anesthetic management. Regional anesthesia, either epidural or subarachnoid block, reduces the incidence of postoperative thromboembolism during total hip arthroplasty.2,3The mechanism by which intraoperative thrombosis occurs is probably related to increased regional blood flow, a by-product of local anesthetic-induced sympathectomy, and to a mild effect on the acute hemostatic reaction to surgery.4Thus, regional anesthesia modulates two branches of Virchow's triad of stasis, hypercoagulability, and intimal damage. Francis et al seemed to have ignored this body of literature by providing data on the incidence of venous thrombosis related only to the type of thrombosis prophylaxis and not to the type of anesthesia also.