Comparison of Arixtra vs. Lovenox to Prevent Blood Clots in Medically Ill Patients

Inclusion Criteria: * Male or female \> 40 years of age. * Pt with expected stay in hospital 6 days or \>, with expectation to be bedridden for \> 4 days. * Pts admitted to the MICU, Regional Heart Units of LV-MHC Exclusion Criteria: * Surgical primary admission diagnosis * Recent surgery within the past 12 weeks * Planned surgery on the current admission * Pregnancy * Vent-dependent respiratory failure requiring intubation for \>24 hours. * Known current DVT or PE prior to enrollment in study. * Creatinine clearance \< 30 mL/min (calculated by the Cockcroft-Gault method) in a well-hydrated patient. * Hx of prior or current lower upper or lower GI bleed. * Platelet count \< 100,000 per cubic millimeter * Current or prior anticoagulation within the prior 48 hours, excluding a single dose \&lor 24 hour period of prophylactic agent * Bacterial endocarditis. * Hemophilia * Hypersensitivity to aspirin. * Hypersensitivity to Arixtra or Lovenox * Hx of hemorrhagic or ischemic stroke \< 3 months prior to enrolling * Hematocrit \< 28%. * SBP \>200 mmHg or DBP \>120 mmHg * Positive for occult blood in stool. * Admission to hospital for \> 48 hours prior to randomization * Documented congenital or acquired bleeding disorder * Indwelling intrathecal or epidural catheter * Life expectancy \< 30 days * Inability to have a flu assessment post-discharge from the hospital