(909) Anti-Xa Monitoring for Venous Thromboembolism Prophylaxis in Patients With Burn Injuries

Introduction: Patients with burn injuries are at increased risk of venous thromboembolism (VTE). Higher intensity enoxaparin dosing with anti-Xa (AXA) monitoring and dose adjustment has been suggested to decrease the risk of VTE in the burn population. Our burn center implemented a weight-based enoxaparin protocol with AXA monitoring in late 2022. The purpose of this study was to determine the characteristics of AXA monitoring in our burn population.

Methods: This retrospective review evaluated adult (≥18 years) patients admitted to the burn unit at a large academic medical center from January to December 2023 who had at least one peak AXA level drawn after ≥3 prophylactic enoxaparin doses. The primary outcome was the percentage of patients who achieved a goal peak AXA level (0.2-0.4 IU/mL). Secondary outcomes included incidence of VTE with and without goal AXA levels and time to first goal AXA level (from admission and first enoxaparin dose). Descriptive statistics were performed.

Results: One-hundred twenty-five patient admissions were included. One-hundred nine admissions (77%) achieved a goal AXA level. Patients who achieved a goal AXA level had 9% total body surface area (TBSA) burns, versus 4% TBSA burns in patients without a goal AXA level. Median weight was 96 kg in the goal AXA group versus 97 kg in the group without goal AXA levels. Four patients (3.2%) developed a VTE during enoxaparin therapy. Three had achieved goal AXA concentrations when the VTE occurred, and one was receiving subcutaneous heparin at the time of VTE. The mean time from enoxaparin initiation to the first AXA level was 1.7 (1.2-2.2) days. The median time to first goal AXA level was 4.4 (2.1-6.9) days from admission and 3.2 (1.5-6.1) days from initial enoxaparin dose.

Conclusions: Most patients achieved a goal AXA level. Weight and burn size were similar between patients who achieved and did not achieve goal AXA levels. Incidence of VTE was low, though most patients who developed VTE had achieved goal AXA levels. Additional modification to our VTE prophylaxis protocol is warranted to determine optimal dosing to decrease time to goal AXA level.