title: Warfarin prophylaxis and venous thromboembolism in the first 5 days following hip and knee arthroplasty.
abstract: Many orthopaedic surgeons use warfarin to prevent venous thromboembolism (VTE) following hip or knee arthroplasty. Since warfarin's antithrombotic effects are delayed, we hypothesized that early VTE (occurring within 5 days post-operatively) would be more common in arthroplasty patients receiving warfarin monotherapy compared to those receiving enoxaparin. We performed a secondary analysis of a case-control study examining risk factors for post-operative thrombosis in postmenopausal women. We defined cases as patients who were diagnosed with thrombosis within 5 days of surgery. Controls without thrombosis were matched with cases by age, surgeon, year of surgery and surgical joint. 84 women with early post-operative thrombosis (cases) were matched with 206 controls. 18 cases (21.4%) had been prescribed warfarin mono-therapy, compared with 7 controls (3.4%). 58 (69.1%) cases and 195 (94.7%) controls had been prescribed subcutaneous enoxaparin 30 mg twice daily, starting 12-24 hours after surgery. The odds ratio for any early thrombosis in patients receiving warfarin as opposed to enoxaparin 30 mg twice daily was 8.6 (p<0.0001). For proximal thrombosis, the odds ratio was 11.3 (p<0.0001). Multivariate analysis did not alter these findings. Warfarin's delayed antithrombotic effects may not provide adequate VTE prophylaxis in the immediate post-operative setting. We suggest caution in employing warfarin monotherapy following joint arthroplasty.
authors.affiliation: Department of General Internal Medicine, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA. brotmad@ccf.org
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Brotman
authors.forename: Amir K
authors.initials: AK
authors.lastname: Jaffer
authors.forename: Jason G
authors.initials: JG
authors.lastname: Hurbanek
authors.forename: Nariman
authors.initials: N
authors.lastname: Morra
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D016022:Case-Control Studies; D004341:Drug Evaluation; D017984:Enoxaparin / Q000008:administration & dosage; D005260:Female; D006801:Humans; D016017:Odds Ratio; D011183:Postoperative Complications / Q000517:prevention & control; D011292:Premedication; D012189:Retrospective Studies; D013923:Thromboembolism / Q000188:drug therapy / Q000209:etiology / Q000517:prevention & control; D013995:Time; D020246:Venous Thrombosis / Q000188:drug therapy / Q000209:etiology / Q000517:prevention & control*; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D017984:Enoxaparin; D014859:Warfarin