Study: Survival odds after cardiac arrest depend on which EMS agency shows up

The EMS agency that responds to an out-of-hospital cardiac arrest could affect a patient's odds of survival, but the actual factors involved remain unknown. (Photo by katifcam/iStock/Getty Images Plus/Getty Images)

The odds of survival among patients who experience out-of-hospital cardiac arrest vary quite a bit depending on which EMS agency treats them, according to a new study published in JAMA Cardiology.

In fact, the study found a median difference of 56% in the odds of survival for any two similar cardiac arrest patients treated by different EMS agencies, even after controlling for known sources of variability.

The study looked at a large data set, covering over 40,000 individuals across 112 different EMS agencies in the United States and Canada between April 2011 and June 2015. 

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While previous studies have shown variations in survival metrics due to factors such as patient demographics, timely administration of CPR or defibrillation by EMS or laypeople, and overall EMS response time, particularly in rural areas, controlling for those factors didn’t reduce the variation observed in this study, according to the study’s lead author, Masashi Okubo, M.D., M.S.

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“Initially, we expected that median outcome variations would decrease as we included more patient factors, but actually the median observation increased slightly,” Okubo, who is clinical instructor of emergency medicine and a research fellow at the University of Pittsburgh School of Medicine, told FierceHealthcare.

That finding suggests some combination of unmeasured factors must be causing the variation.

Study data included information about chest compressions performed across EMS agencies, which proved consistent and conformed with current guidelines.

The study notes that the best-performing EMS agencies tended to have more personnel on the scene to administer care, suggesting one potential area of future study. Other recommendations include evidence-based guidance on the decision-making process behind transporting a patient for further care or improvements in the way EMS agencies build and train their teams.

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Addressing this variation in care quickly presents a problem, however. The current study is the first to quantify patient outcome variation after adjusting for known factors, which means it will take more work and study to identify best practices before EMS agencies will be able to put them into use in the field.

“The issue is, there’s no universal or standard benchmarks or metrics for EMS performance,” Okubo said.

Since the variation likely has multiple causes and the study has ruled out the most likely known candidates, researchers will have to go back to the drawing board to look for metrics that do make a difference before they can develop a set of best practices.

“Without measuring, it’s very difficult to improve,” he said.

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