Introduction: Trauma patients have both bleeding and venous thromboembolism (VTE) risk, but prophylaxis recommendations are lacking for patients on anticoagulants prior to admission. This study compares bleeding after VTE prophylaxis initiation between low molecular weight heparin anti-Factor Xa (anti-Xa) monitoring to no monitoring prior to prophylaxis initiation in trauma patients on apixaban or rivaroxaban (DOAC). Methods: Adults admitted to a single level 1 trauma center on DOAC prior to arrival were included. Exclusion criteria were admission anti-Xa 1 anti-Xa (monitored) or ≤1 anti-Xa (empiric). The primary outcome was bleeding events after VTE prophylaxis initiation. Secondary outcomes were bleeding after 24 hours, VTE incidence and anti-Xa threshold for prophylaxis initiation. Multivariate logistic regression analyses (MVLR) were performed to identify bleeding and VTE risk factors. Results: A total of 506 patients (248 monitored; 260 empiric) were included. Bleeding after prophylaxis initiation occurred less in the monitored cohort (10.9% vs. 16.1% p=0.05). Bleeding after 24 hours was not different between cohorts (25% vs. 20%, p=0.12). VTE events were no different between cohorts (1.5% vs. 2.8%, p=0.32). An anti-Xa of 0.5 IU/mL was identified as a possible threshold for VTE prophylaxis initiation. ICU admission was an independent risk factor for bleeding after VTE prophylaxis initiation (OR 3 95% CI 1.6-5.5) whereas anti-Xa monitoring was protective (OR 0.4 95% CI 0.3-0.8). Body mass index >30 kg/m2 was an independent risk factor for VTE (OR 8.4 95% CI 2-25.8). Conclusions: Anti-Xa monitoring prior to VTE prophylaxis initiation was associated with reduced bleeding after VTE prophylaxis initiation in trauma patients on DOAC prior to admission with no difference in VTE incidence. Further research is warranted to confirm the optimal anti-Xa concentration for VTE prophylaxis initiation.
Krabacher et al. (Sun,) studied this question.