How Can We Improve Survival from Out-of-Hospital Cardiac Arrest?

I’ve spent the majority of my medical career working in critical care. Rarely has a week passed by when I haven’t treated someone who’s suffered an out-of-hospital cardiac arrest (OHCA). My approach to treating these patients has barely changed over the years. If the patient is unconscious, they’re intubated and ventilated for 72 h and provided with all the organ support they need. Throughout this time, they remain fully sedated and their temperature is carefully controlled. Once we’ve identified and treated the cause of their cardiac arrest, we step back and leave the nursing staff to get on and deliver the essential day-to-day care that the patient needs. At the same time, we also sit down with friends and relatives and explain what’s going on. We try our best to avoid raising expectations. A figure of 10% is often quoted—that’s an estimate of the percentage of patients with OHCAs in the United Kingdom who survive to hospital discharge. ¹ To lower expectations even further, we warn loved ones that many of those who make it are often left with life-changing complications. When the sedation is eventually stopped, it soon becomes clear that most patients have suffered a catastrophic neurological insult, and with the family’s support, plans are carefully made to move toward palliative treatment.

Our success stories tend to be predictable—they’re the ones who are lucky enough to receive some form of cardiopulmonary resuscitation (CPR) and defibrillation “on the scene.” Survival rates can climb to more than 70% if patients in ventricular fibrillation receive defibrillation within 5 min of cardiac arrest. ² But we know that in remote rural communities like ours, the chances of this happening are rare. Nevertheless, some do make it. I remember 2 cases in particular—a marathon runner who collapsed at the feet of the finish line paramedic and a grandmother who arrested outside the fire station, just yards from trained help and an automated external defibrillator (AED). These survivors show just what’s possible when patients receive prompt and effective care. It’s what many refer to as the “chain of survival”—a series of steps that, when linked closely together, dramatically increase the likelihood of surviving an OHCA. Although we can debate what’s the most important link in the chain, few will argue that what matters most are the actions taken in the first few seconds following a collapse. Success depends upon recognizing a cardiac arrest and requesting help, immediate CPR, and rapid use of a defibrillator. Put plainly, the intervals between collapse to CPR and collapse to defibrillation are the leading factors that determine survival. Although this has been widely known for many years, enormous variation in survival exists. For outcomes to improve, it is essential to identify best practice and promote it as widely as possible.

Over the years, authors of Wilderness & Environmental Medicine (WEM) have taken a close interest in OHCA. DeClerck and colleagues ³ looked at 18,675 medical events that took place in areas controlled by the US National Park Service between 2007 and 2011. They identified 327 cardiac arrests that resulted in no fewer than 232 (71%) deaths. Authors have reported dramatic differences in outcomes. Mikiewicz et al ⁴ reported a total of 74 OHCAs that were treated by members of Poland’s Tatra Mountain Rescue Service. Only 8 (11%) went on to have a “good or moderate neurological outcome.” Contrast this with the results of Morton and colleagues ⁵ in this issue of WEM, who describe a case series of 10 OHCAs that occurred during organized outdoor sporting activities. Given early identification of cardiac arrest and rapid treatment, 80% went on to make a full recovery. Such differences are seen in wider society. The 2021 report from the Cardiac Arrest Registry to Enhance Survival showed that survival from OHCA ranged from 2% to 18% among different emergency medical services providers in the United States. ⁶ Only by collecting these data is it then possible to shape policy and deliver meaningful improvements in care.

Although it’s likely that the majority of OHCAs are triggered by underlying cardiovascular diseases, WEM authors have also described a number of other causes—from anaphylaxis and avalanche burial to trauma, drowning, and ingestion of poisonous plants. In some cases, resuscitation was successful. Bhatnagar and Mackman ⁷ described a remarkable case of a 57-y-old man who was brought into their emergency department in cardiac arrest with a core temperature of 23°C. Following 5 h of rewarming and resuscitation, the patient eventually recovered. The next day, he regained consciousness and on discharge, appeared to have made a full neurological recovery. In this case, CPR was made easier by the use of a mechanical chest compression device. Pietsch et al ⁸ described their use of a LUCAS-2 in a skier who suffered a cardiac arrest following avalanche burial. On a steep mountain slope, the rescuers felt that the device was not only capable of providing high-quality chest compressions but also made it easier to transport and treat the victim.

The benefits of an AED have also been acknowledged in WEM. DeClerck found high levels of use (64%) by the US National Park Service that may go some way to explaining the finding that no fewer than 29% in his study survived to hospital discharge. ³ In the study by Mikiewicz et al, ⁴ the use of an AED led to 56% of victims surviving an OHCA compared with just 14% of those who did not. Findings like these have led the International Commission for Mountain Emergency Medicine to recommend in the pages of WEM that such devices should be placed in all mountain areas that see high numbers of visitors. ⁹ To work most effectively in the mountains, the authors highlight the importance of using a biphasic device that works well in wet conditions and across a wide range of temperatures. However, as Joslin and Biondich ¹⁰ wrote in a subsequent WEM editorial, defibrillation is only one link in the “chain of survival.” Unless OHCA victims can be identified, treated, and evacuated quickly, an AED will make little or no difference in patient outcome.

In the future, I hope authors will continue to shine a spotlight on OHCAs. If the past is anything to go by, we’ll learn more about where cardiac arrests take place, what triggers them, and importantly, the treatment that victims receive. Above all, I’d encourage authors to seek out ways in which the “chain of survival” can be strengthened. Here are just a few ideas: Can telecommunications be used to better connect those on the ground with rescue services and hospital staff? In the United Kingdom, the GoodSAM App has been shown to be an effective way of not only alerting first responders to an OHCA but also improving outcomes. ¹¹ Will it be possible for drone technology to be used to rapidly deliver resuscitation equipment to those who need it? This was highlighted in a recent case study from Sweden, where an autonomous drone was able to dispatch an AED to the home of an OHCA victim, which allowed defibrillation in advance of the paramedic crew reaching the patient. ¹² With the advent of new technology, is there the potential to widen the use of extracorporeal membrane oxygenation in OHCA? Although research has yet to show an improvement in survival, an increase in successful organ donation among extracorporeal membrane oxygenation recipients suggests that further research is warranted. ¹³

So whether it’s through advances in technology, training, or techniques, at WEM, we’re eager to highlight the ways in which outcomes from OHCAs can be improved.

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