Change associated with enoxaparin prophylactic anti-Xa levels during prolonged hospitalization in trauma patients.

BACKGROUND: The administration of optimized venous thromboembolism (VTE) prophylaxis is critical in trauma patients. Guidance thus far has focused on initial enoxaparin dose selection and anti-factor Xa (anti-Xa) level monitoring. The need for monitoring and titrating prophylaxis in high-risk patients requiring prolonged hospitalization remains unknown. METHODS: This was a retrospective, single-center, cohort study including patients admitted with traumatic injury between January 1, 2021, and November 1, 2025, receiving enoxaparin for chemoprophylaxis and requiring prolonged hospitalization (>14 days). The primary outcome characterized clinically significant change in enoxaparin anti-Xa levels between the first level resulting within prophylactic target range and a repeat level obtained at least 6 days later resulting outside of prophylactic target range. Secondary outcomes evaluated the incidence of thrombus and clinically significant bleeding during the index hospitalization. RESULTS: Of 272 consecutive patients screened, 43 patients were included within the study period. The patient cohort exhibited a median Injury Severity Score (ISS) of 21 [13.5-27] on admission. A total of 46 repeat anti-Xa levels were obtained at least 6 days following the first anti-Xa level within prophylactic target range. Clinically significant change in repeat anti-Xa levels was observed in 12/46 (26%) instances. The majority of repeat anti-Xa levels resulted in subtherapeutic range (10/12, 83.3%). The incidence of thrombus occurred in 7/43 (16.3%) patients and clinically significant bleeding in 1/43 (2.3%) patients during the index hospitalization. CONCLUSIONS: Approximately one-quarter of patients exhibited clinically significant change between the first anti-Xa level within prophylactic target range and repeat anti-Xa levels obtained at least 6 days later in this evaluation. Subsequent larger studies are necessary to validate these hypothesis generating findings.