Use of Low Molecular Weight Heparin (Tinzaparin) to Treat Blood Clots in Patients With Kidney Failure

Blood clots in the leg veins, known as deep vein thrombosis, are important because they may travel to the lung (known as pulmonary embolism) and cause death. Blood clots are treated with blood thinners, or anticoagulants. The preferred treatment is an anticoagulant known as low molecular weight heparin (LMWH). LMWH is given by an injection under the skin, which is convenient for patients because they can self-administer this medication at home, and no blood testing is required. However, LMWH is cleared from the body through the kidneys, so patients who have kidney failure are generally not treated with LMWH because they may be at a higher risk of bleeding. One type of LMWH, known as tinzaparin, may be less dependent on the kidneys for clearance and may not increase in patients with kidney failure. The investigators would like to use tinzaparin to treat patients who have deep vein thrombosis or pulmonary embolism, and who also have kidney failure. The purpose of this study is to determine whether the blood thinning effects of tinzaparin build up, or accumulate, in patients with varying degrees of kidney failure compared to patients without kidney failure. The blood thinning effects will be measured using a blood test known as an anti-Xa level. Patients will be followed over the time they receive tinzaparin and those patients who are found to have potentially high levels of tinzaparin (based on the anti-Xa level) will have their tinzaparin dose adjusted. The investigators believe that the levels of tinzaparin will not accumulate to potentially dangerous levels in a significant number of patients with kidney failure.