Western Journal of Emergency Medicine: Integrating Emergency Care with Population Health

Introduction: Emergency medical services (EMS) redirection is used to manage emergency department (ED) strain, but whether it reflects operational conditions is unclear. We compared associations of prespecified ED operational measures, including visit volume, patient flow times, admissions, boarding, and left-early measures, with redirection activation and total daily redirection minutes.

Methods: We performed a retrospective study at a single urban tertiary care center over 392 consecutive days from April 7, 2021 through May 3, 2022. Redirection temporarily routed ambulances away from the study hospital and was activated centrally by EMS. New York City’s 9-1-1 system included about 500 ambulance units and over 60 hospitals. The primary outcome was activation, defined as any redirection during a calendar day. The secondary outcome was total redirection minutes among days with redirection. Multivariable logistic regression evaluated activation, and negative binomial regression evaluated duration.

Results: Redirection occurred on 250 of 392 days (63.8%). Median daily duration was 47 minutes (interquartile range 23-78). Higher ED visit volume was associated with activation (odds ratio [OR] 1.14 per 10 patients; 95% CI, 1.02-1.27). Longer door-to-room time was associated with activation (OR 1.42 per 5 min; 95% CI, 1.04-1.92) and duration (incidence rate ratio 1.022 per min; 95% CI, 1.002-1.042). Boarding time and admission count were not associated with either outcome.

Conclusion: Emergency department visit volume was associated with activation but not duration, while door-to-room time was associated with both. Evaluating redirection as a single outcome may obscure differences between activation and cumulative duration.