 The study protocol uses a VTE prevention regimen that employs rational pharmacologic principles and is in line with published recommendations for prophylaxis in this patient population. In consideration of having a comparator cohort group, we would consider it to be unethical to have a cohort group receiving enoxaparin 40 mg subcutaneously once daily as a comparator group because pharmacologic data strongly suggests that effective levels of anticoagulation would not be achieved in this population of patients. 8 Informed consent was felt optimal in order to allow patients to fully understand that this regimen, although it is an acceptable standard of care, is being employed under the broader context of a study whereby other patient data will be collected and recorded in prospective fashion. Once informed consent is obtained, patients will begin VTE prophylaxis with enoxaparin 0.5 mgkg subcutaneously once a day. Peak anti-Xa activity will be obtained in all patients through a venipuncture 4-6 hours after the first or second dose has been given. Five milliliters of blood will be drawn. This is the amount of blood that is needed for this laboratory test to be performed. Baseline clinical and demographic information will be obtained and recorded on standard case reporting forms, CRF see Appendix B. Patients will continue prophylaxis as deemed necessary by their attending physician through the duration of their hospital stay or unless dictated otherwise by the patients attending physician. Adverse events such as VTE, bleeding event, or thrombocytopenia will be recorded during the hospital stay see Appendix C. 