(1594) Achievement of Prophylactic Anti-Xa Levels in Trauma Patients Receiving Enoxaparin

Introduction: Venous thromboembolism (VTE) is a common cause of morbidity and mortality in trauma patients. Subcutaneous enoxaparin 30 mg every 12 hours has been commonly adopted as prophylaxis, but studies assessing this regimen have found that many patients do not achieve prophylactic anti-Xa peak levels. The current prophylactic enoxaparin regimen for trauma patients at UVA Health consists of 30 mg, 40 mg, or 60 mg every 12 hours for patients < 100 kg, 100 kg to 179 kg, and ≥180 kg, respectively. The goal of this study was to determine what proportion of patients achieve prophylactic anti-Xa peak levels on this regimen, as well as its efficacy and safety.

Methods: This retrospective, single center, descriptive case series assessed patients admitted to the UVA Health trauma service receiving enoxaparin for VTE prophylaxis with an anti-Xa level measured within 3 to 5 hours after at least 3 consecutive enoxaparin doses. The primary outcome was the proportion of peak anti-Xa levels within the goal range of 0.2-0.4 IU/mL. Secondary outcomes were rates of VTE, and the rate of patients requiring packed red blood cell (PRBC) transfusions. Baseline characteristics were assessed for their relationship to achievement of prophylaxis.

Results: Of 465 patients screened, 99 met criteria for inclusion. Fifty-six patients (56%) had anti-Xa peak levels within the prophylactic range, 33 (33%) were subprophylactic, and 11 (11%) were supraprophylactic. Four patients (4%) developed VTE, all of which had subprophylactic anti-Xa peak levels (p= 0.023). There was no significant difference in the rate of patients requiring PRBC transfusions between prophylactic groups. Significant differences in achievement of prophylaxis were noted with relation to age, weight, body mass index, milligram per kilogram dose, and creatinine clearance.

Conclusions: Among trauma patients receiving enoxaparin for VTE prophylaxis at UVA Health, only 56% achieve prophylactic anti-Xa peak levels. Those with subprophylactic anti-Xa peak levels were significantly more likely to develop VTE. Analysis of baseline characteristics suggests that achievement of prophylaxis is influenced by a variety of patient specific factors. These findings align with those of prior studies, suggesting the need for individualized enoxaparin dosing for trauma patients.