The epidemiology of venous thromboembolic events in a severe trauma cohort admitted to the intensive care unit of an Australian major trauma centre over a five-year period

• Incidence of new VTE within 28 days of injury was 12%. PE incidence 5%, 20% in pulmonary artery. Lower limb DVT 8% proximal location 61%. • First VTE prophylaxis in 76% of cohort was subcutaneous unfractionated heparin, median dose 5000 units Q12H, commencement 48 hours post injury. • In those that hadn’t experience competing risks, severe lower extremity injury or increasing weight were associated with increased rate of VTE. • Increasing ISS and severe head injury increased rate of death and decreased rate of discharge alive, however were not associated with VTE risk. Incidence of new VTE within 28 days of injury was 12%. PE incidence 5%, 20% in pulmonary artery. Lower limb DVT 8% proximal location 61%. First VTE prophylaxis in 76% of cohort was subcutaneous unfractionated heparin, median dose 5000 units Q12H, commencement 48 hours post injury. In those that hadn’t experience competing risks, severe lower extremity injury or increasing weight were associated with increased rate of VTE. Increasing ISS and severe head injury increased rate of death and decreased rate of discharge alive, however were not associated with VTE risk. Venous thromboembolism (VTE) is a major contributor to morbidity and mortality following traumatic injury. The optimal pharmacological VTE prophylaxis (VTEp) regimen is uncertain. There are limited data on VTE events and VTEp practice, particularly in the trauma population requiring admission to an intensive care unit (ICU). To describe the incidence and timing of VTE events, VTEp regimens, and associated risk factors for VTE in a severe trauma cohort requiring ICU admission. Retrospective cohort study of all trauma patients (n=969) admitted to the ICU of the Royal Brisbane and Women’s Hospital between 1/2/19 and 31/12/23. Data collected included baseline characteristics, VTEp administered, VTE investigations and outcomes including VTE events, length of stay, and mortality. Competing risks survival analysis was used to describe the association between baseline characteristics and risk of VTE development. The median injury severity score was 22 (IQR 16-29). The incidence of new VTE events, as diagnosed on imaging, within 28 days of injury was 12%. The median time to first VTE event was 9 days (IQR 4.8-13.1), and 5 of the 121 (4%) events occurred within 24h of injury. In the group that were admitted within 24h of injury, the median time to VTEp commencement was 48h (IQR 29-71) and 74% received unfractionated heparin as the first VTEp administered. In those that had not experienced the competing risks of death or hospital discharge, only the presence of a severe lower extremity injury (cause specific HR 1.81, 95% CI 1.19-2.76, p = 0.005) and increasing weight (cause specific HR 1.02, 95% CI 1.01-1.03) were associated with an increased adjusted rate of developing a VTE by day 28. Although the incidence of VTE in our cohort was lower than reported in international studies, it remains a significant burden of disease. These data can be used to inform the design of clinical trials that seek to address the evidence gaps in the optimal post-trauma VTEp regimen in the severely injured trauma population.