Study Design, Setting and Population

In a prospective case-cohort study, all trauma patients transported to the Mayo Clinic Emergency Department (ED) by ambulance or air transport, as a level 1 or 2 trauma activations, from February 2011 to June 2014 were considered for study inclusion (Table 1). Exclusion criteria were prior history of VTE, age < 18 years, anticoagulation (e.g., heparin, warfarin) or antithrombotic therapy (excluding aspirin or non-steroidal anti-inflammatory drugs), preexisting coagulopathy, more than 12 hours from time of injury, no blood drawn within first 12 hours after injury, active cancer, sepsis, renal failure, burn injuries or declined consent by the patient or legal guardian (Figure 1). The time of injury (TOI) was determined by the pre-hospital medical providers based on information at the injury scene. If the TOI was unclear, the pre-hospital medical providers estimated the time and relayed this information to the emergency communication center. A trauma alert page was then sent to the hospital and laboratory staff as to the TOI. We collected demographic, baseline and time-dependent clinical characteristics, including injury severity score (ISS), patient age and sex, body mass index (BMI), hospital length of stay (LOS), all-cause mortality, and start and stop of anticoagulant-based thromboprophylaxis and other medications affecting coagulation, trauma injury severity score (TRISS), all injury codes from Mayo Clinic Trauma Registry, transfusion data in the prehospital and for entire index hospitalization, IVC filter placement, and standard admission laboratory data (PT, aPTT, INR, hemoglobin, platelet count). Transfusion therapy was mainly based on Mayo Clinic Trauma Center transfusion guidelines but also at the discretion of the medical provider. This study was approved by the Mayo Clinic Institutional Review Board. All patients were followed forward in time from time of injury (TOI) to the earliest of symptomatic, objectively-diagnosed VTE, death or other loss to follow-up, or 92 days (about 3 months) post hospital discharge.

Enrollment Flow Diagram

Adult Trauma Activation Criteria

Threatened or Compromised Airway or Intubated Patient

Respiratory Distress

Respiratory rate < 10 or >30

Flail chest (known or suspected)

Heart rate > 120 and/or heart rate > systolic blood pressure

Confirmed Systolic BP < 90 at any time

Transfer patients receiving blood to maintain vital signs

St02 ≤ 70%

GCS ≤ 12 associated with injury

Paralysis, loss of sensation, and/or suspected spinal cord injury

Unstable pelvic fracture (known or suspected)

Bilateral femur fractures (known or suspected)

Traumatic amputation/crushed, degloved, mangled or pulseless injury extremity (excluded isolated hand/foot)

Patients with tourniquets to control hemorrhage

Burns > 10% body surface area (2nd/3rd degree) or with any known or potential airway compromise

High voltage electrocution including lightening

Gunshot wound proximal to elbow or knee OR any penetrating injury to head, neck, torso, axilla, or groin

Patients with known, intracranial bleed on anticoagulation (excluding ASA)

Two or more proximal long bone fractures (if bilateral femur = RED) (known or suspected)

Death of restrained passenger in same vehicle

Major auto deformity (intrusion into passenger compartment)

Auto vs Pedestrian/bicyclist/motorcyclist thrown, run over, or with significant (> 20 mph) impact

Ejection (separated from) from motorized vehicle (car, motorcycle/motocross, snowmobile, ATV)

Fall > 20 feet

Suspected brain injury in patient on anticoagulation therapy (excluding ASA)