Warfarin anticoagulation in the perioperative period: is it safe?

This study was undertaken to determine if warfarin anticoagulation could be safely continued during surgery and in the perioperative period. An animal model was followed by a prospective human study of all patients on heparin or warfarin at the time of surgery. Twenty-four rabbits underwent laparotomy, during which a controlled liver injury was created and repaired. Group 1 (Warf) was anticoagulated with warfarin to raise the mean international normalization ratio (INR) to 2.5-3.0. Group 2 (Hep) was anticoagulated with heparin to raise the activated partial thromboplastin time to 1.5-2.0 times control. The heparin was then stopped 6 hr prior to surgery and resumed 6 hr postoperatively without a bolus. Group 3 (control) was not anticoagulated and received saline infusion. For the human study, data were collected on 40 patients undergoing 50 operations from October 1996 to January 1998. The results of this study reveal that (1) bleeding was less in the group anticoagulated with warfarin throughout surgery in the animal model, (2) bleeding complications were less in the patients continued on warfarin through surgery than those on heparin (3) older patients may have an increased risk of bleeding, and (4) an INR of >3 at the time of surgery may increase the risk of bleeding.