Warfarin anticoagulation after total hip or total knee replacement: Clinical and resource-utilization outcomes in a university-based antithrombosis clinic

Purpose: Clinical and resource-utilization outcomes associated with warfarin anticoagulation after major orthopedic surgery were evaluated. Methods: Consecutive patients who received postsurgical prophylaxis with warfarin within 24 hours of total knee replacement (TKR) or total hip replacement (THR) surgery and who were referred to and had outpatient follow-up for anticoagulation management in a single-center, university-based antithrombosis clinic from January 1, 1998, to January 1, 2009, were included in the study. Data were obtained from existing inpatient and outpatient medical records and retrospectively reviewed. Patient follow-up and data collection were conducted from the time of admission until 90 days after surgery. Results: A total of 400 patients were included in the study; 179 (44.8%) under-went THR and 221 (55.3%) underwent TKR. The mean length of hospital stay was 5.0 ± 1.9 days, and the mean length of warfarin therapy was 50 ± 21 days. The mean time required to reach the target International Normalized Ratio (INR) of 2.0-3.0 was 10.0 ± 9.1 days. The within-patient percentage of INR levels spent in the target range was 28% ± 18%. Objectively confirmed symptomatic venous thromboembolism (VTE) occurred in 16 patients (4%), with 14 events (87.5%) occurring with INR values of ≥2.0 and 2 events (12.5%) occurring with INR values of >2.0. Conclusion: THR and TKR surgical patients at one institution who were receiving postsurgical VTE prophylaxis with warfarin spent a substantial proportion of time with their INR below the target range and had a high rate of symptomatic VTE.