Emergency medical services response time and mortality in an urban setting.
BACKGROUND
A common tenet in emergency medical services (EMS) is that faster response equates to better patient outcome, translated by some EMS operations into a goal of a response time of 8 minutes or less for advanced life support (ALS) units responding to life-threatening events.


OBJECTIVE
To explore whether an 8-minute EMS response time was associated with mortality.


METHODS
This was a one-year retrospective cohort study of adults with a life-threatening event as assessed at the time of the 9-1-1 call (Medical Priority Dispatch System Echo- or Delta-level event). The study setting was an urban all-ALS EMS system serving a population of approximately 1 million. Response time was defined as 9-1-1 call receipt to ALS unit arrival on scene, and outcome was defined as all-cause mortality at hospital discharge. Potential covariates included patient acuity, age, gender, and combined scene and transport interval time. Stratified analysis and logistic regression were used to assess the response time-mortality association.


RESULTS
There were 7,760 unit responses that met the inclusion criteria; 1,865 (24%) were ≥8 minutes. The average patient age was 56.7 years (standard deviation = 21.5). For patients with a response time ≥8 minutes, 7.1% died, compared with 6.4% for patients with a response time ≤7 minutes 59 seconds (risk difference 0.7%; 95% confidence interval [CI]: -0.5%, 2.0%). The adjusted odds ratio of mortality for ≥8 minutes was 1.19 (95% CI: 0.97, 1.47). An exploratory analysis suggested there may be a small beneficial effect of response ≤7 minutes 59 seconds for those who survived to become an inpatient (adjusted odds ratio = 1.30; 95% CI: 1.00, 1.69).


CONCLUSIONS
These results call into question the clinical effectiveness of a dichotomous 8-minute ALS response time on decreasing mortality for the majority of adult patients identified as having a life-threatening event at the time of the 9-1-1 call. However, this study does not suggest that rapid EMS response is undesirable or unimportant for certain patients. This analysis highlights the need for further research on who may benefit from rapid EMS response, whether these individuals can be identified at the time of the 9-1-1 call, and what the optimum response time is.
Emergency Medical Services, Alberta Health Services, Calgary, Alberta, Canada.
Ian E
IE
Blanchard
Christopher J
CJ
Doig
Brent E
BE
Hagel
Andrew R
AR
Anton
David A
DA
Zygun
John B
JB
Kortbeek
D Gregory
DG
Powell
Tyler S
TS
Williamson
Gordon H
GH
Fick
Grant D
GD
Innes
D000293:Adolescent; D000328:Adult; D022561:Advanced Cardiac Life Support; D000368:Aged; D000416:Alberta; D000552:Ambulances; D016001:Confidence Intervals; D017598:Efficiency, Organizational / Q000706:statistics & numerical data*; D004632:Emergency Medical Services / Q000706:statistics & numerical data*; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends*; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D018570:Risk Assessment; D016019:Survival Analysis; D013997:Time Factors; D014505:Urban Population / Q000706:statistics & numerical data*; D055815:Young Adult