COMPARISON OF 2 WARFARIN REGIMENS IN THE PREVENTION OF VENOUS THROMBOSIS FOLLOWING TOTAL KNEE REPLACEMENT

A prospective, randomized trial was conducted to compare the effective ness and safety of warfarin given in two regimens in prevention of ven ous thrombosis after total knee replacement. Adult patients scheduled for primary or revision total knee replacement were randomly assigned to receive either a ''two-step'' warfarin regimen beginning 10-14 days pre-operatively or, alternatively, to begin warfarin the night before surgery. Post-operatively, the dose was adjusted in both groups to ac hieve a target International Normalized Ratio (INR) of 2.2 and prophyl axis was continued until venography on post-operative days five throug h nine. Bleeding was assessed by surgical blood loss, transfusion requ irements, changes in hematocrit, and clinically identified bleeding co mplications. The occurrence of deep vein thrombosis was nearly the sam e in the two treatment groups, 39% in patients randomized to the two-s tep regimen as compared to 38% in those beginning the night before sur gery. The occurrence of proximal vein thrombosis was also similar, 5% versus 7% (p = NS). Patients in the tyro-step group received 1.33 +/- 1.26 transfusions compared to 0.95 +/- 1.22 in the night before group (p <0.05) and also had a lower nadir post-operative hematocrit of 26.7 +/- 3.1 as compared to 28.5 +/- 3.2 (p <0.0001). Major bleeding compl ications were associated with excessively prolonged INRs and occurred in five patients in the two-step group and two in the night before gro up. Patients in both groups who developed thrombosis had a significant ly lower INR on post-operative days two and three compared to those wi thout thrombosis. We conclude that a prophylactic warfarin regimen for prevention of deep vein thrombosis after total knee replacement begin ning the night before surgery is more convenient and may be associated with less bleeding than a regimen beginning warfarin 10-14 days pre-o peratively. Careful control of anticoagulant intensity is needed to ac hieve maximum effectiveness and avoidance of bleeding complications.