Antithrombin to Improve Thromboprophylaxis and Reduce the Incidence of Trauma-Related Venous Thromboembolism

Inclusion Criteria: * Admission to trauma service * Polytraumatic injuries OR pelvic/long bone fracture * Planned admission to trauma ICU or step-down/SIMU setting (this includes STICU, SIMU/TIMU, BICU, and BIMU) * Informed consent obtained Exclusion Criteria: * Prisoners (defined as those directly admitted from correctional facility) * Known or suspected pregnancy * ≥ 20% total body surface area (TBSA) burned * Nonsurvivable head injuries * Known hematologic or immunologic disorders * Known prehospital anticoagulant use * Patients initially placed on unfractionated heparin for thromboprophylaxis * Known allergy to Antithrombin or it's components * Enrollment in another interventional study unless approved by Trial Principal Investigator