For example, a person may have a high risk of bleeding, a side effect of thinning the blood. In these cases, a surgical procedure can be done. This involves inserting a filter in one of the major veins of the body that leads to the heart. This filter catches any clots that break off so they cannot get into the lungs and cause death. Heparin can cause bleeding and lower blood platelet counts, called thrombocytopenia.
Warfarin can also cause bleeding, which in rare cases is fatal.
Warfarin interferes with many other medications. Surgery can cause bleeding, infection, or allergic reaction to anesthesia . Most patients with a deep venous thrombosis will recover fully. When DVT is in the pelvis or upper leg, warfarin is usually taken for at least three to six months. DVT in the veins of the calf is usually treated with warfarin for at least six weeks.