Emergency department (ED) and hospital overcrowding cause offload delays that remove emergency medical services (EMS) crews from service and compromise care delivery. Prolonged ED boarding and delays to inpatient care are associated with increased hospital length of stay (LOS) and patient mortality, but the effects of EMS offload delays have not been well studied.

We used administrative data to study all high-acuity Canadian Triage Acuity Scale 2–3 EMS arrivals to Calgary adult EDs from July 2013 to June 2016. Patients offloaded to a care space within 15 minutes were considered controls, whereas those delayed ≥ 60 minutes were considered “delayed.” Propensity matching was used to create comparable control and delayed cohorts. The primary outcome was 7-day mortality. Secondary outcomes included hospital LOS and 30-day mortality.

Of 162,002 high-acuity arrivals, 70,711 had offload delays <15 minutes and 41,032 had delays > 60 minutes. Delayed patients were more likely to be female, older, to have lower triage acuity, to live in dependent living situations, and to arrive on weekdays and day or evening hours. Delayed patients less often required admission and, when admitted, were more likely to go to the hospitalist service. Main outcomes were similar for propensity-matched control and delayed cohorts, although delayed patients experienced longer ED LOS and slightly lower 7-day mortality rates.

In this setting, high-acuity EMS arrivals exposed to offload delays did not have prolonged hospital LOS or higher mortality than comparable patients who received timely access.