(1596) A Weight-Based Enoxaparin Protocol for Venous Thromboembolism Prophylaxis in Trauma Patients

Introduction: Venous thromboembolism (VTE) contributes to significant morbidity and mortality in the trauma population. Fixed dose VTE prophylaxis schematics may be inadequate. This study describes a pharmacist monitored weight-based enoxaparin prophylaxis schematic. Enoxaparin 0.5 mg/kg twice daily is adjusted to a peak anti-Xa concentration of 0.2-0.5 units/mL. The objectives were to determine impact on VTE event rates, assess achievement of goal anti-Xa concentration, and elucidate which patient subgroups benefit from therapeutic drug monitoring.

Methods: This multicenter retrospective analysis of trauma patients admitted to acute care hospitals from 4/1/2020-11/30/2020 included all patients who received weight-based enoxaparin for prophylaxis. Patients were excluded if they received anticoagulation for any indication prior to admission. The primary outcomes were detection of VTE during hospitalization and percentage of peak anti-Xa concentrations in the goal range of 0.2-0.5 units/mL.

Results: There were 702 patients with a median age of 59 years, 56% being male, median weight of 80 kg, median body mass index (BMI) of 28 kg/m2, and median creatinine 84 mL/min. Eight patients had a detectable VTE during hospitalization. 321 patients (46%) had anti-Xa concentrations drawn and 217 (67%) were in the goal range of 0.2-0.5 units/mL. Of those not within range, median age was 69 years old, 65% were women, median weight was 90 kg, and median creatinine clearance was 55 mL/min. One patient had a subtherapeutic level requiring a dose increase. 103 patients had supratherapeutic anti-Xa concentrations, requiring dose reductions.

Conclusions: Our pharmacist driven protocol utilizing enoxaparin 0.5 mg/kg twice daily adjusted to a goal peak anti-Xa concentration of 0.2-0.5 units/mL achieved goal anti-xa concentrations in 67% of patients, with the majority of out-of-range concentrations being supratherapeutic. For patients who were < 120 kg, had creatinine clearances > 45 mL/min, and were < 65 years of age, enoxaparin displayed predictable pharmacokinetics and met the goal anti-Xa concentration 98% of the time, suggesting that anti-Xa monitoring may not be necessary in these subgroups. VTE event rates and rates of clinically significant bleeding were similar to previous studies.