Why 30 mg Twice Daily Fails: Anti-Factor Xa Monitoring and the Persistent Dosing Gap in High-Risk Trauma Patients

Introduction Contemporary trauma guidelines support higher initial enoxaparin dosing for adult trauma patients, as standard dosing (30 mg twice daily [BID]) frequently fails to achieve target anticoagulant activity. While anti-factor Xa (anti-Xa) monitoring guides dose adjustments, real-world implementation of follow-up monitoring remains variable. This study evaluated anti-Xa target attainment, dose escalation practices, and completion of follow-up monitoring in high-risk trauma patients. Methods This retrospective cohort study at a Level I trauma center included adult trauma patients (April 2022-October 2023) receiving enoxaparin venous thromboembolism prophylaxis who underwent at least one anti-Xa measurement. Demographics, Injury Severity Score (ISS), dosing changes, and repeat monitoring frequencies were analyzed. This study evaluated real-world clinical practice and was not designed to compare dosing strategies or assess a protocolized intervention. Results Among 244 patients (median ISS 22; 43% with BMI >40 kg/m 2 ), 80% initially received standard dosing (30 mg BID). Only 42% achieved target prophylactic anti-Xa levels (0.2–<0.5 IU/mL). Of those on standard dosing, 34% required escalation, with the mean adjusted dose approaching 40 mg BID. While 68% of patients who underwent repeat testing after dose escalation successfully achieved target levels, repeat monitoring was completed in only 22% of all adjusted patients. Venous thromboembolism occurred in 5%, and bleeding in 7%. Conclusion Standard enoxaparin dosing frequently fails high-risk trauma patients, supporting contemporary higher-dose guidelines. However, a critical implementation gap persists; while clinicians recognize subtherapeutic levels and escalate doses, follow-up anti-Xa monitoring is inconsistently performed. Standardized tracking protocols and automated electronic triggers are required to close the loop in anti-Xa pathways.