No, Do NOT Be Still My Beating Heart

I was reading a recent article about a trailside incident in one of my favorite national parks, Zion, in Springdale, Utah. A hiker apparently had a cardiac event, and unfortunately passed away. According to the story, it sounds as if trained people were available to start CPR, but after 90 minutes, it was decided to stop resuscitative efforts and he was unfortunately pronounced dead.  

Ninety minutes is a long time for someone to get CPR, and it reminded me of a question we sometimes get at our classes, which is "how long should someone continue to administer CPR?"

There isn't a straightforward answer, so let's dig into some of the nuance.

First, the amount of time between a cardiac event and the initiation of CPR will have an impact on the chances of success. As soon as it's determined the a person does not have a pulse, CPR should be started. 

"For every minute without CPR, survival from witnessed VF cardiac arrest decreases by 7–10%," and with bystander CPR, the "decrease in survival is more gradual and averages 3–4% per minute from collapse to defibrillation."

Multiple studies have shown that early high quality CPR can save lives.

But, one important component to the success of CPR is that it really is just a temporizing measure until a defibrillator, and then definitive care (hospital) is available. 

I don't want to get too deep in the weeds here, and I'll do a few other articles on both possible precipitants of cardiac arrest, and the physiology behind CPR, but the short story is that ventricular fibrillation is the most common cause.

Ventricular fibrillation (vfib or VF) is an electrical shit storm where the nice, orderly flow of electricity that makes the heart beat has gone haywire. In some cases, medications can *help* but in reality you have to fight electricity with electricity, and that's what an AED (automated external defibrillator) does. 

So, a person goes down, we assume it's due to vfib, but we can start CPR until an AED arrives. In some cases, an AED will confirm that it's vfib and a shock will be advised, in other cases, it will due to another cause, and the AED will not offer any benefit. It's back to CPR...

Here are some salient points:

• Early defibrillation is critical for survival from SCA [sudden cardiac arrest] for several reasons. 
• Firstly, the most frequent initial rhythm in witnessed SCA is VF. 
• Secondly, the treatment for VF is electrical defibrillation. 
• Thirdly, the probability of successful defibrillation diminishes rapidly over time. 
• Finally, VF tends to deteriorate to asystole within a few minutes.
• Therefore, defibrillation as soon as possible is the standard care for VF. 
• In a study of over 12 000 patients treated by EMS, 4546 had witnessed VF. 
• For these patients a shorter defibrillation response interval was significantly correlated with an increased chance of survival to hospital discharge.
• In a study of 148 patients with out‐of‐hospital cardiac arrest in US casinos, 105 had VF. The survival rate was 74% for victims who received their first defibrillation within the first 3 min after collapse. For those who received their first defibrillation after the first 3 min, the survival rate was only 49%.
• Therefore, early defibrillation is useful and effective if applied within 4–5 min of onset of out‐of‐hospital cardiac arrest.

So, early CPR is great as long as an AED is on the way (or already on hand, as many are now found in public places). If you're waiting for EMS to bring one, there could be a delay, especially if you're miles into the woods. 

The goal of EMS response times as quickly at 4 minutes were discussed in A US National Study of the Association Between Income and Ambulance Response Time in Cardiac Arrest:

"Many EMS systems have adopted benchmarks to arrive on scene in less than 4, 8, and 15 minutes, with aims to deliver early CPR and defibrillation by trained professionals based on evidence by Eisenberg et al and others, which demonstrated a survival benefit of CPR performed within 5 minutes and defibrillation within 9 minutes of collapse for patients with cardiac arrest."

I can't see that happening that quickly on the trails. Which brings us back to the unfortunate incident at Zion National Park. Yeah, maybe someday drones will bring AEDs to the field, but we're not there yet.

If CPR is started, when should it stop? It's great to possibly be a hero and literally save someone's life, but here are some stats:

• Despite recent advancements in CPR care, data has shown that both prehospital and hospital-related CPR outcomes are exceedingly poor.
• Estimates are that less than 11% of patients suffering from out of hospital cardiac arrest (OHCA) survive to discharge from the hospital.
• The subset of those patients who survive with favorable neurological status is even lower, with studies showing those rates anywhere between 2 to 9% of all patients with OHCA.
• Once a patient suffers a cardiac arrest, the chance of achieving a return of spontaneous circulation (ROSC) ranges from 7.2 to 11%. 
• Furthermore, studies have shown that the survival rate declines when the duration of CPR is greater than 10 minutes without ROSC and rapidly declines after 30 min.

That's all pretty grim, but these studies include all patients who suffer a cardiac arrest, and the chance of a "good" outcome for a 92yr old with multiple medical conditions versus a 65yr old who is healthy enough to be hiking or biking or running will be vastly different.

Either way, the longer the brain goes without good oxygenation and the longer the heart goes without defibrillation, the chance of poor outcomes goes up.

In "Duration of Prehospital Resuscitation Efforts After Out-of-Hospital Cardiac Arrest" authors state: 

• "On the basis of results from the 2 shockable arrest groups, prehospital resuscitation efforts should be continued for at least 40 minutes from call receipt, including at least 33 minutes of EMS responder resuscitation efforts from scene arrival, in all adult patients with bystander-witnessed OHCA [Out of Hospital Cardiac Arrest] to achieve a ≥99% sensitivity of favorable 30-day neurological outcome."

However, this graph from Relationship Between the Duration of Cardiopulmonary Resuscitation and Favorable Neurological Outcomes After Out‐of‐Hospital Cardiac Arrest: A Prospective, Nationwide, Population‐Based Cohort Study shows "the dynamic probability of 1‐month survival and 1‐month survival with favorable neurological outcomes by CPR duration. After 20 minutes of CPR, the probability of favorable 1‐month outcomes decreased from 36.8% (95% CI: 36.1–35.5%) to 4.6% (95% CI: 4.3–4.9%), for survival, and from 21.8% (95% CI: 21.3–22.5%) to 1.9% (95% CI 1.7–2.1%) for survival with favorable neurological outcomes. Furthermore, after 30 minutes of CPR, the rate of favorable outcomes decreased to 0.8% (95% CI: 0.7–1.0%) for survival and to 0.4% (95% CI: 0.3–0.5%) for survival with favorable neurological outcomes. None of the patients who received CPR for more than 53 minutes survived." The important point in there for me is "after 20 minutes of CPR, the probability of favorable 1‐month outcomes decreased from 36.8% to 4.6% for survival, and from 21.8% to 1.9% for survival with favorable neurological outcomes" (my bolding).

And, in UpToDate, one of the risk factors for poor prognosis is "prolonged CPR more than five minutes."

So what is it? Five minutes? Twenty Minutes? Forty Minutes? Six and a half hours?

Both the previous NAEMSP guidelines and the current European Resuscitation Council recommend 20 minutes of on-scene efforts before terminating efforts.

Beyond those previous guidelines, there are no clear recommendations, at least for bystanders. For trained EMS providers (ALS and BLS), and other healthcare providers, we do have criteria that can be followed to know when resuscitative efforts are futile.  

I *think* 20-30 minutes of high quality CPR is a heroic effort and unless help is imminently on the way, anything more than that is unlikely to be beneficial. Would I keep trying? Probably, but there would be a point in which it's just not going to help. Hopefully if you ever find yourself in this situation, you'd have a 911 professional on the phone who could help provide guidance.

Heavy stuff to think about, so I'll try to change the mood with some Kelly Clarkson.

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