Randomized Assessment of a Warfarin Nomogram for Initial Oral Anticoagulation after Venous Thromboembolic Disease

Standard treatment for venous thromboembolism is parenteral heparin followed by warfarin. In this study we assess whether a standardized method of ordering warfarin reduces the duration of hospitalization. Consecutive patients were randomized to receive warfarin managed by attending physicians or by a nomogram. Patients were stratified according to primary or secondary venous thromboembolism. Prothrombin times were measured daily and heparin was given for a minimum of 5 days and stopped when the International Normalized Ratio was >1.9. Patients were followed for 3 months. There were 111 patients, 80 with primary and 31 with secondary venous thromboembolism. Overall there were no differences between the two warfarin groups with respect to length of admission. Given the prolonged duration of admission in many patients with secondary venous thromboembolism, a subset analysis was conducted on the 80 patients with primary venous thromboembolism. Patients in the standard group stayed significantly longer than patients in the nomogram group (6.0 vs. 5.6 days, p = 0.02). The warfarin nomogram as tested is safe and leads to a significantly shorter length of stay for patients with primary venous thromboembolism as compared to standard practice.