Does Delayed Response Due to Busy Ambulances Impact Risk of Death and Hospital Service Use?: A Cohort Study of 240,000 Medical Emergencies.

Objectives: When ground ambulances are busy with any task, delays are likely for concurrent emergencies. Whereas time-critical conditions are affected by delays, general impacts remain unclear. We aimed to assess how delayed ambulance response due to busy ambulances affects risk of death and use of hospital services.

Methods: We studied individuals with out-of-hospital emergencies that precipitated a call to the medical emergency number in Central Norway from 2013 to 2022. Emergency service and hospital data were linked to assess subsequent death and hospitalizations. We addressed potential bias by multivariable adjustment and a natural experiment: For emergencies that occurred in the same area at similar times, we compared outcomes for patients with differences in busy ambulances to analyze delays in response that were arguably unrelated to prioritization due to the patient severity.

Results: Among 239,320 acute emergencies, 4.1% of patients died within 7 days. An interquartile range of variation in the probability a busy ambulance was associated with a 2.9-minute delay (95% confidence interval [CI] = 2.8, 3.0). Overall, a 5-minute delay was associated with a risk difference of 0.10 percentage points in the risk of death (95% CI = -0.17, 0.36) and 1.24 for hospitalization (95% CI = 0.59, 1.94). The cost of hospital treatment within 1 year increased by 616 euros (95% CI = 183, 1069).

Conclusion: While we found no substantial increase in the overall risk of death associated with delayed ambulance response, the observed rise in hospital costs suggests a potential increase in morbidity.