PERIOP 2 - A Safety and Effectiveness of LMWH vs Placebo Bridging Therapy for Patients on Long Term Warfarin Requiring Temporary Interruption of Warfarin.

5,000 iu or 200 iu/kg depending on the type of surgery injection will be given subcutaneously, once a day for a minimum of 4 days or until the INR is 2.0

"patients will be randomized post-operative to receive either active treatment or placebo.~the placebo will be given as a subcutaneous injection once a day. the amount of the placebo will be equivalent to the active treatment depending on the type of surgery.~ie. 5,000 iu or 200 iu/kg"