Effectiveness of Emergency Department-Initiated Thromboprophylaxis Protocols in Reducing Venous Thromboembolism in High-Risk Patients: A Systematic Review

Venous thromboembolism (VTE) remains a leading cause of preventable morbidity and mortality among hospitalized patients. Although pharmacological thromboprophylaxis is well established in inpatient care, initiation is frequently delayed until after hospital admission. The emergency department represents the first point of contact for many high-risk patients and a potential opportunity for earlier prevention. This systematic review and meta-analysis evaluated the effectiveness of emergency department-initiated thromboprophylaxis protocols in preventing VTE among high-risk adult patients. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review was conducted using MEDLINE, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials from inception to the most recent update. Eligible studies included randomized controlled trials and observational or quasi-experimental studies evaluating thromboprophylaxis initiated in, or directly facilitated by, the emergency department. Outcomes of interest included incidence of VTE, bleeding complications, mortality, length of stay, and process measures such as prophylaxis utilization and timeliness. Risk of bias was assessed using the Risk of Bias 2 (RoB 2) tool for randomized trials and the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool for non-randomized studies. Due to substantial clinical and methodological heterogeneity, quantitative pooling was limited, and a structured narrative synthesis was performed. The review identified a heterogeneous body of evidence comprising prospective and retrospective cohorts, before-and-after implementation studies, and health information technology interventions. Emergency department-initiated or emergency department-facilitated protocols consistently increased appropriate thromboprophylaxis use and reduced delays to the first dose. In a subset of large protocol implementation studies, earlier initiation was associated with lower rates of symptomatic VTE without a corresponding increase in major bleeding. Mortality and length of stay outcomes were inconsistently reported, precluding definitive conclusions. The overall certainty of evidence was limited by observational designs, variability in patient populations, and inconsistent outcome definitions. Emergency department-initiated thromboprophylaxis protocols improve the timeliness and appropriateness of VTE prevention and may reduce symptomatic events without increasing bleeding risk in selected high-risk populations. These findings support the integration of structured thromboprophylaxis pathways into emergency care, while highlighting the need for high-quality prospective trials to define their impact on patient-centered outcomes.