Introduction and Objectives: The use of aspiration drainage in knee replacement is associated with an increase in postoperative bleeding. We assessed the affectivity of a 4 hour delayed opening of the drainages.

Materials and Methods: Retrospective comparative study. We studied 122 cases divided into 2 groups that underwent total knee replacement with different guidelines for drainage opening during the postoperative period. In one group the drainage was opened immediately, in the other after a 4 hour delay. We assessed the amount of fluid drained and also possible modifying factors. We also assessed associated complications.

Results: We found significant differences in the amount of fluid drained between the drainages opened immediately and at 4 hours. With the use of drainage opened at 4 hours there is a non-significant decreasing trend in the need for transfusions; there is no significant increase in local complications at the wound site or at the site of the arthroplasty.

Discussion and Conclusions: Keeping drainages closed during the first 4 hours of the postoperative period is a cost-effective way of decreasing bleeding in TKR surgery.