Anti-Xa Monitored Compared to Empiric Initiation of VTE Prophylaxis in Trauma Patients on DOAC

Sunday, March 22, 2026

11:00 AM - 12:00 PM Central Time

Location: Connections Central - RST 09

Samuel Krabacher, PharmD

University of Cincinnati Medical Center

Disclosure(s): No relevant financial relationship(s) to disclose.
MD

Molly Droege, PharmD

Clinical Pharmacy Specialist
University of Cincinnati Medical Center

Disclosure information not submitted.
PB

Paige Garber Bradshaw, BCCCP, PharmD

Clinical Pharmacy Specialist, Critical Care
University of Cincinnati Medical Center

Disclosure information not submitted.
MF

Madeline Foertsch, PharmD, BCCCP, BCPS

Clinical Pharmacy Specialist, Neuro-Critical Care
University of Cincinnati Medical Center

Disclosure information not submitted.
CD

Chris Droege, PharmD, FCCP, FCCM

Clinical Pharmacy Manager
University of Cincinnati Medical Center

Disclosure information not submitted.
CB

Chris Bollinger, PharmD, MBA

Clinical Pharmacy Specialist
University of Cincinnati

Disclosure information not submitted.
AM

Amy Makley, MD

Associate Professor of Clinical Director of Trauma
University of Cincinnati Medical Center

Disclosure information not submitted.
CP

Carolyn Philpott, BCCCP, PharmD

Clinical Pharmacy Specialist; Surgery, Trauma, and Orthopedics
University of Cincinnati Medical Center

Disclosure information not submitted.

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 < 0.1 IU/mL, no anticoagulant within seven days of admission, pregnancy, and incarceration. Patients were grouped based on anti-Xa monitoring prior to VTE prophylaxis initiation: >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.