(1769) Evaluation of Anti-Xa Levels in Obese Trauma Patients Receiving Enoxaparin for Chemoprophylaxis

Introduction: Traumatic injury increases the risk of venous thromboembolism (VTE) events in critically ill patients and may lead to worse outcomes. Obese trauma patients possess additional risk factors for developing VTE and often require higher doses of VTE prophylaxis. Guidelines recommend enoxaparin as the first line agent for VTE prophylaxis in trauma patients and anti-Xa levels are recommended to guide dose adjustments in patients with extremes of body weight. The purpose of this study is to evaluate anti-Xa levels in relation to BMI-stratified enoxaparin regimens for obese patients and assess subsequent adverse effects.

Methods: A single-center retrospective chart review was conducted from November 2023 to February 2024 at an urban level 1 trauma center. Inclusion criteria consisted of trauma patients with a BMI >30 kg/m2 that received enoxaparin 50 mg or 60 mg twice daily for VTE prophylaxis and had at least one anti-Xa level. Exclusion criteria applied to protected populations. The primary objective was to evaluate the rate of anti-Xa levels within goal range (0.2-0.4 IU/mL) when drawn appropriately based on BMI-stratified enoxaparin dosing. Levels were considered appropriate when obtained at steady state (after third dose of regimen) and within peak (3-5 hours). Key secondary objectives included rate of appropriately timed levels, VTE, and hemorrhage.

Results: Twenty-seven patient encounters were reviewed with a median BMI of 38.4 kg/m2 (interquartile range of 33.3-45.7 kg/m2). The most common VTE prophylaxis regimen was enoxaparin 50 mg every twelve hours (85.7%). Of the appropriate levels obtained, 55.6% fell within the target anti-Xa range. Of all the anti-Xa levels obtained for this cohort, 33.3% were drawn and collected appropriately. In patients with appropriately timed anti-Xa levels within goal range, there was one episode of minor bleeding and no VTE events.

Conclusions: In trauma patients with a BMI >30 kg/m2, over half of the appropriately timed anti-Xa levels were within target range based on BMI-stratified enoxaparin regimens. While incidence of appropriately timed levels was low overall, rates of associated adverse effects remained minimal.