Outcome-Informed Emergency Medical Services Response Planning: A Systematic Review

Emergency medical services (EMS) commonly use standardized call interrogation systems to determine response strategies. The findings of caller interrogation are typically combined with local clinical and operational guidelines to determine EMS response plans. These plans dictate assigned resource type and response priority, often with associated response time targets. It is unclear whether EMS response plans have been prospectively aligned with patient outcomes and evaluated in terms of diagnostic accuracy or predictive performance measures. This review examines evidence on the prospective alignment of EMS response plans with linked patient outcomes and the effects of implemented system-level changes.

A systematic review was conducted following preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines. Electronic databases were searched for studies evaluating ambulance dispatch response assignment informed by linked patient outcomes. Eligible studies (1) prospectively aligned EMS response plans with linked patient outcomes and (2) evaluated the impact of implemented system-level changes utilizing linked patient outcomes via diagnostic accuracy or predictive performance measures. Studies were excluded if they were a single-priority system, did not evaluate fully implemented plans or evaluated single condition changes only. The risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal for Quasi-Experimental Studies.

Of the 2677 identified studies, only three studies met the inclusion criteria, representing a combined total of 2,956,071 EMS responses. All three were non-randomized and quasi-experimental. Outcome measures included short-term mortality, response time performance for high-acuity calls, emergency department presentation, lights-and-sirens utilization, and dispatch accuracy. Narrative synthesis was performed. Directional findings across the three different study interventions were consistent. The evaluated outcome-informed EMS response plans were associated with reduced high-priority responses and improved system efficiency, with no clear evidence of harm. Certainty of evidence was unable to be assessed. Substantial heterogeneity in the study design, outcomes assessed, and analytic approaches used precluded data synthesis, and limits the certainty and generalizability of the findings.

Evidence evaluating linked patient outcome-informed optimization of EMS response plans remains limited and heterogenous but offers preliminary insight into the feasibility of such approaches. Additional research is needed to evaluate the effectiveness, reproducibility, and generalizability of system-level response plan optimization.