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Have 2005 AHA Guidelines Improved Cardiac Arrest Survival?


Review Of: Hinchy PR, Myers JB, Lewis R, et al. Improved out-of-hospital cardiac arrest survival after the sequential implementation of 2005 AHA guidelines for compressions, ventilations and induced hypothermia: The Wake County experience. Ann Emerg Med. 2010;4:348–357, 2010.  

The Science
This is an observational multi-stage "before and after" study assessing survival from out-of-hospital cardiac arrest after implementation of the 2005 American Heart Association (AHA) guidelines in an urban/suburban community. During a span of 48 months, investigators observed a baseline (use of 2002 AHA guidelines); Phase 1 (implementation of 2005 AHA guidelines); Phase 2 (implementation of an Impedance Threshold Device (ITD); and Phase 3 (induction of therapeutic hypothermia). The results showed a significant overall increase in survival rates of 7.3%. A significant increase in return of spontaneous circulation was found from baseline to Phase 3, from 24.7% to 43.4%, respectively. Baseline to Phase 1 saw the greatest increase (24.7% to 40.1%). The investigators conclude that with a communitywide sequential implementation of the 2005 AHA guidelines for compression, ventilation and induced hypothermia, survival rates from cardiac arrest can be increased.

The Street
Medic Marshall and Doc Wesley discuss the pros and cons of this study's approach to cardiac arrest survival.

Medic Marshall
This study takes a shotgun blast approach to the notion of improving cardiac arrest survival and then attempts to identify the silver bullet within that blast that led to increased survival. Unfortunately, although the investigators weren’t able to find their silver bullet, they did demonstrate that the shotgun approach works.

When you dive deeper into this study, you find so many variables that it's difficult to point to the single most important thing that improved survival. Was it the decrease in time to defibrillation or the increase in bystander CPR? These are only a few of the questions one is left with after reading this study. One thing it does, however, is show that cardiac arrest survival is everyone's responsibility–from recognition all the way through a patient's hospital stay. As out-of-hospital providers, we need to realize that we're just one cog in the system, but we can make a substantial impact on improving outcomes through a variety of ways, such as developing community education on awareness of the importance of early recognition and CPR, working with first responders on improving CPR effectiveness, facilitating community training in AED use, maintaining our training and education…the list goes on.

At the end of the day, this study shows a significant overall improvement in cardiac arrest survival. However, it was only through a systematic approach that the researchers were able to demonstrate such a vast improvement.

Doc Wesley
I was looking forward to this study for more than a year, and frankly, I’m disappointed. It promised to be one of the first to determine what, if any, impact the 2005 AHA guidelines have on cardiac arrest survival. Unfortunately, even as the authors state, they don’t know what improved survival, but they do know that by doing everything survival improved.

There was a significant change in care provided to their patients prior to the arrival of the paramedics. First, witnessed arrests rose significantly between the baseline and Phase 1 and leveled off. Second, first responders with AEDs arrived in less than four minutes almost twice as often during implementation than during the baseline. Because of these two factors, the percentage of patients in VF/FT rose significantly. It is possible that these two factors alone could account for the dramatic rise in survival. Though it is not clearly stated in the article, Dr. Hinchey, one of the authors, assures me that their regression analysis indicates that these were not the factors that increased survival.

Don’t get me wrong. I’m all in favor the 2005 guidelines with their emphasis on quality CPR and the use of the ITD. However, this study did not show that these guidelines in and of themselves improved survival. This is demonstrated by the fact that there was no significant improvement in survival between Phase 1, Phase 2, and Phase 3. Again, I asked Dr. Hinchey for his opinion and he told me something profound. “We are medical directors, not researchers. We can’t wait until we have a statistically large number of cases before changing our protocols with steps we feel improve outcomes. As medical directors, we are responsible for our citizens care.” I completely agree with my colleague. In a perfect world we would only perform randomized, double-blind research before changing our practice, but that doesn’t fit with the realities of caring for our patients.



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