The influence of oral anticoagulation therapy on deep vein thrombosis rates four weeks after total hip replacement

Purpose: The purpose of this study was to assess the rate of postoperative deep vein thrombosis (DVT) as a function of oral anticoagulation therapy af ter total hip replacement surgery. Methods: A total of 125 patients completed the study. All the patients rece ived sequential gradient pneumatic compression over elastic stockings until hospital discharge. In addition, all the patients underwent postoperative heparin therapy followed by oral warfarin therapy, adjusted in dose to main tain a goal international normalized ratio (INR) level of 2.0 to 3.0. Warfa rin therapy and compression stockings were continued for 1 month after surg ery. Bilateral duplex scanning was performed 1 and 4 weeks after surgery to assess the rate of DVT. Results: Nineteen of the 125 patients had DVT develop (15.2%). Of those thr omboses, six (31.6%) and 13 (68%) were detected 1 week and 1 month after su rgery, respectively. The rate of proximal DVT was 2.4% (3 of 125) 1 week af ter surgery and rose to 8.2% (10 of 122) 1 month after surgery. Most DVT ca ses (64%; 12 of 19) were asymptomatic. The patients in whom DVT developed h ad significantly lower INR values during the second to fourth postoperative weeks than did those patients without thrombosis, and no differences in IN R values were found during the first postoperative week. Conclusion: The risk of the development of DVT extends beyond hospital disc harge in patients who undergo total hip replacement, despite a regimen of p rolonged oral anticoagulation therapy. This is particularly true in patient s whose INR values did not reach therapeutic range during the first postope rative month. Therefore, thrombosis prophylaxis regimens on the basis of th e administration of warfarin should try to maintain INR values within thera peutic range during the entire first postoperative month to minimize the in cidence of DVT.