Evaluation of Venous Thromboembolism Prevention in High-Risk Trauma Patients

This is a pilot study to determine if AT-III serum concentrations differ between patients
with normal (>= 0.1 IU/mL) versus subtherapeutic (<0.1 IU/mL) anti-Xa trough concentrations
when placed on enoxaparin 30 mg twice daily for venous thromboembolism (VTE) prophylaxis.
Secondarily, this study will compare two enoxaparin dosing strategies: standard 30 mg twice
daily and a dosing strategy based on trough anti-Xa values in high-risk trauma patients.

Specific aims include: 1) to compare the extent of reduced AT-III activity between patients
with trough anti-Xa >= 0.1 IU/mL and < 0.1 IU/mL upon initial assay; 2) to determine the
proportion of patients who reach goal anti-Xa and the time to goal anti-Xa achievement
between two interventional dosing strategies: enoxaparin 40 mg every 12 hours (with
consideration to increase to 50 mg every 12 hours if recheck anti-Xa is not at goal) and
enoxaparin 30 mg every eight hours; 3) to compare anti-Xa enoxaparin dosing strategies based
on VTE, bleeding rates, transfusion requirements, drug discontinuation rate and
bioaccumulation, and 4) to determine patient-specific factors that correlate to
subtherapeutic anti-Xa such as serial AT-III activity, weight, body mass index, age,
cumulative fluid administration, and thromboelastography (TEG).

Inclusion Criteria:

- Multi-system trauma

- Anticipated length of stay of at least 72 hours

- At high risk (risk adjustment profile [RAP] >= 5) and initiated on enoxaparin 30 mg
every 12 hours per VTE prophylaxis protocol

- No counterindication to trauma team VTE prophylaxis protocol (e.g., intracranial
bleeding, incomplete spinal cord injury with hematoma within 24 hours post injury,
ongoing hemorrhage, uncorrected coagulopathy, >= grade IV liver or spleen injury,
intraocular injury)

Exclusion Criteria:

- Renal dysfunction (creatinine clearance < 30 mL/min or on continuous renal replacement
therapy)

- Weight < 50 kg or > 150 kg

- Platelet count < 50,000

- Allergy to heparin or low molecular weight heparin

- On therapeutic anticoagulation on admission or requiring it within 24 hours of
admission

- Isolated intracranial hemorrhage

- Known hyperbilirubinemia (serum bilirubin > 6.6 mg/dL)

- Pregnancy

- Incarceration