Predictors of direct oral anticoagulant concentrations in the trauma population.

Introduction: Direct oral anticoagulant (DOAC) use is becoming more prevalent in patients presenting after trauma. We sought to identify the prevalence and predictors of subtherapeutic and therapeutic DOAC concentrations and hypothesized that increased anti-Xa levels would correlate with increased risk of bleeding and other poor outcomes. Methods: A retrospective cohort study of all trauma patients on apixaban or rivaroxaban admitted to a level 1 trauma center between January 2015 and July 2021 was performed. Patients were excluded if they did not have a DOAC-specific anti-Xa level at presentation. Therapeutic levels were defined as an anti-Xa of 50 ng/mL to 250 ng/mL for rivaroxaban and 75 ng/mL to 250 ng/mL for apixaban. Linear regression was used to identify correlations between study variables and anti-Xa level, and binomial logistic regression was used to test the association of anti-Xa level with outcomes. Results: There were 364 trauma patients admitted during the study period who were documented to be on apixaban or rivaroxaban. Of these, 245 patients had anti-Xa levels measured at admission. The population was 53% woman, with median age of 78 years, and median Injury Severity Score of 5. In total, 39% of patients had therapeutic and 20% had supratherapeutic anti-Xa levels. Female sex, increased age, decreased height and weight, and lower estimated creatinine clearance were associated with higher anti-Xa levels at admission. There was no correlation between anti-Xa level and the need for transfusion or reversal agent administration, admission diagnosis of intracranial hemorrhage (ICH), progression of ICH, hospital length of stay, or mortality. Conclusions: Anti-Xa levels in trauma patients on DOACs vary widely; female patients who are older, smaller, and have decreased kidney function present with higher DOAC-specific anti-Xa levels after trauma. We were unable to detect an association between anti-Xa levels and clinical outcomes. Level of evidence: III-Prognostic and Epidemiological.