Impact of Violations of the Shortest Distance-Based Transport Protocol for Intra-Arrest on Clinical Outcomes in a Metropolitan City: A Large-Scale Registry Study

Background/Objective: The optimal strategy for hospital transport of patients with out-of-hospital cardiac arrest is unclear. A transport protocol based on the shortest travel route was implemented in a metropolitan area in the Republic of Korea to minimize prehospital transport time; however, the protocol is frequently violated. This study evaluated whether protocol violations influenced the clinical outcomes of patients who experienced intra-arrest. Methods: This retrospective observational study included patients who experienced out-of-hospital cardiac arrest and were transported by emergency medical services between September 2021 and December 2022. We analyzed run sheets, the cardiac arrest registry, and Out-of-Hospital Cardiac Arrest Surveillance data, which contain patient demographics, time variables, Utstein factors, posthospital arrival treatments, and clinical outcomes. The primary outcome was emergency department mortality. The secondary outcome was poor neurological outcome (cerebral performance category scores 3–5). Logistic regression and mediation analyses assessed associations between protocol violations, transport times, and clinical outcomes. Results: Among the 3474 cardiac arrest cases, 1534 (44.2%) had transport protocol violations. Violations were associated with longer scene and transfer times. The emergency department survival rates for the protocol-violation and -nonviolation groups were 15.4% and 16.4%, respectively. Protocol violations were not associated with mortality (odds ratio [OR]: 1.04; 95% confidence interval [CI] 0.85–1.27, p = 0.70) or poor neurological outcomes (OR: 1.00; 95% CI 0.45–2.18, p = 0.99). Mediation analysis revealed that increased transfer time did not affect clinical outcomes. Conclusions: These results suggest that transport strategies should consider real-time availability of emergency resources and adopt an evidence-based approach.