A surgical procedure requires reversal of oral anticoagulation to guarantee adequate hemostasis during and after the operation. This does not generally apply, however, to low dose (8 1 mg/d) aspirin therapy since, unlike high-dose antiplatelet drug therapy, it is not associated with increased perioperative bleeding. The key to management of a patient on long-term warfarin therapy is to minimize the “unanticoagulated” interval and the associated risk for a thromboembolic event. Patients maintained at an INR of 2-3 can usually be managed by discontinuing their oral anticoagulant 4 days prior to their surgery to reach an INR below 1 .5 on the day of surgery. This time interval wi ll al low a return of depressed coagulation factors, in patients with normal liver function, to levels above 30%. If the patient has a higher chronic INR range (> 3), then warfarin should be discontinued 5-6 days prior to the procedure. If surgery is urgent, the time delay to “normalizing the INR” can be shortened by the administration of vitamin K or an infusion of fresh frozen plasma. However, while the INR may appear to rapidly shorten with vitamin K therapy, this is largely a result of a rapid retum of factor VII, not factors IX, X, and II (prothrombin), which still require several days to recover. In addition, vitamin K therapy can make it extremely difficult to reinstitute warfarin therapy after surgery. Fresh frozen plasma must be given in volumes up to 1-1 .5 L (one-third of the estimated plasma volume in a patient with an INR >2 and factor levels.