Many patients who take warfarin (Coumadin) for atrial fibrillation (AF) or cardiac valve pathology must discontinue anticoagulant therapy prior to surgery. Is it safe to suspend the Coumadin for a few days before and after surgery? What is the risk of thrombotic emboli, e.g., causing a stroke, if Coumadin is withheld for five to seven days? Are there any guidelines for maintaining patients on heparin while Coumadin is discontinued? Can low-molecular-weight heparin (LMWH) be used? If so, what are the recommended doses?
—Fadi I. Jabr, MD, Florence, Ore.
Patients with AF have an annual risk of thrombosis between 1% and 12%, the lowest risk being in those with AF alone. Patients with valve prosthesis have variable annual risks depending on type and number of valves and valve position. Prior guidelines suggest that the risk with bileaflet or tilting disk valves in the aortic position is low enough not to warrant bridging anticoagulation during discontinuation of warfarin prior to surgery. In this era of LMWH, however, I would favor its use in the interim. According to guidelines presented at the Seventh Annual American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy (Chest. 2004;126[3 Suppl]:204-233), options for management during the perioperative period are as follows: (1) For low-risk patients, stop warfarin four days preoperatively, then briefly use postoperative prophylaxis with unfractionated heparin (UFH) or LMWH while simultaneously beginning warfarin.
Alternatively, for operations with low risk of bleeding, you can reduce the intensity of anticoagulation and operate at an international normalized ratio (INR) of 1.3-1.5. (2) For high-risk patients, discontinue warfarin four days preoperatively. Begin therapy with a full dose of UFH or a full dose of LMWH as the INR falls (approximately two days preoperatively). UFH can be given as an outpatient subcutaneous injection and then as a continuous IV infusion after hospital admission in preparation for surgery. Discontinue UFH approximately five hours before surgery. It is also possible to continue with subcutaneous UFH or LMWH and to stop therapy 12-24 hours before surgery.
—Norma M. Keller, MD (108-17)