Monday, September 29, 2008

Surviving Cardiac Arrest: Location, Location, Location

Some places are just safer to live than others.

A study by Nichol et al in the latest issue of the Journal of the American Medical Association estimates one's chances of surviving a cardiac arrest in 10 different sites in North America: Regional Variation in Out-of-Hospital Cardiac Arrest Incidence and Outcome.

ResearchBlogging.orgNichol G, Thomas E, Callaway CW, Hedges J, Powell JL, Aufderheide TP, Rea T, Lowe R, Brown T, Dreyer J, Davis D, Idris A, Stiell I. (2008). JAMA, 300 (12), 1423-1431

Their study population included 20,520 patients with out-of-hospital cardiac arrest (OHCA), and concluded that there are significant regional differences in survival.

This study estimated 3 different survival rates: all cardiac arrests, all arrests in which resuscitation was attempted, and all arrests with shockable rhythms. I've summarized these 3 rates for 9 of the 10 centers in the bar chart below.

The top of the red bar is the survival rate for all cardiac arrests.

Many of the 20,520 arrests were not resuscitated, for various reasons (do-not-attempt-resuscitation directives, terminal illness, etc.). The top of the green bar represents survival for those who did receive resuscitation.  As one can see, it's a lot better to be resuscitated than not resuscitated.

Not all cardiac arrests are equal. Patients with arrest due to ventricular fibrillation and other shockable rhythms have a much better chance of survival than arrests from other causes. The top of the blue bar represents their survival rate.

The Pacific Northwest has a reputation of being a great place to live. The plot above suggests it is also a great place to survive a cardiac arrest.

Nichol et al conclude:
These findings have implications for prehospital emergency care. The 5-fold variation in survival after EMS-treated cardiac arrest and 5-fold variation in survival after ventricular fibrillation demonstrate that cardiac arrest is a treatable condition. However, only 31.4% of treated cardiac arrests (84.8% of bystander-witnessed) received bystander CPR. Therefore, ongoing efforts are necessary to encourage the public to be ready, willing, and able to provide CPR when necessary.

Further improvements in outcome could be achieved by reducing the time to arrival of EMS providers capable of advanced cardiac life support by improving early detection of cardiac arrest, dispatch protocols, deployment of existing vehicles, number of vehicles available to respond, quality of CPR, and real-time or postevent quality assurance.
The same issue of JAMA also includes an editorial by Sanders and Kern, from which I have filched the title of this post. Their editorial puts Nichol's study nicely in perspective. As they point out, although OHCA has a dismal prognosis in many communities, even small improvements in survival translate into thousands of lives saved.

From the graph above, it's apparent that someone in Seattle deserves enormous props for achieving the survival rates shown. However, as Sanders and Kern note:
...protocol and technique can be more important than location for survival of OHCA. Focused attention and improvements to identified local issues within the chain of survival can significantly influence survival.
In other words, similar rates of survival should be achievable by any community that cares enough to do so. Sanders and Kern conclude:
It is time to work to overcome barriers in each community, devote appropriate resources, and optimize survival of all patients so that location by city becomes a minor factor in survival of cardiac arrest.


Toshi said...

Hi Samurai Radiologist!

You mention that someone in Seattle probably deserves some credit for their spectacular survival rates. If you didn't intend for that question to be rhetorical, that credit would surely go to Dr. Copass, no?

-Toshi, PGY-2 radiology resident of UW origins

The Samurai Radiologist said...

@ Toshi: I agree. Dr. Copass deserves a lot of credit in Seattle specifically and throughout the whole continent generally with regard to ER protocols, the EMT concept itself, and cardiac resuscitation.