The risk of developing a blood clot occurs in up to 60% of all critical care patients. Many times enoxaparin (or Lovenox) is given to patients who are at a higher risk of developing clots in their legs or lungs. There are two standard doses of enoxaparin that are recommended by the drug companies. These two doses have never been directly compared in trauma, general, and vascular surgery patients. The purposes of this study are: