| Risk stratification for thromboembolism risk is essential. High risk is defined as one or more of the following; the risk increases with the number of risk factors present: |
| • Risk factors for thromboembolism, especially if multiple. Risk factors include: |
| 1. Atrial fibrillation |
| 2. A prior history of thromboembolism |
| 3. Heart failure or a left ventricular ejection fraction ≤30 percent |
| 4. A hypercoagulable state |
| • A mechanical valve in the mitral position. |
| • Mechanical valves known to be associated with a high risk of valve thrombosis if the INR is low (Lillehei Kaster, Omniscience, Starr Edwards). |
| • Surgery for cancer or an infection, both of which can be associated with a hypercoagulable state. |
| The following approach is recommended based upon risk stratification for both thromboembolism and the risk of bleeding, which varies with the site of surgery: |
| • For very high-risk patients, anticoagulation should not be interrupted if possible. |
| • Interruption of anticoagulation is not necessary for many minor surgical procedures, including dental extraction, and for procedures where bleeding can be easily controlled. In such patients, the INR should be lowered to a goal of 2.0 and surgical homeostasis should be meticulous. |
| • If anticoagulation must be interrupted: |
| 1. The patient should be admitted to the hospital and warfarin discontinued |
| 2. Intravenous unfractionated heparin (goal aPTT 1.5 to 2.0) should be started as the INR gradually falls. The safety of subcutaneous low molecular weight heparin started at home has not been established. |
| 3. Heparin and warfarin should be resumed as soon as possible after surgery; heparin is continued until the INR is within the goal therapeutic range. |
