Bystander use of AEDs doubles cardiac arrest survival rates

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Survival from cardiac arrest doubled when a bystander stepped in to apply an automated external defibrillator (AED) before emergency responders arrived, according to research. According to the American Heart Association, of the more than 350,000 out-of-hospital cardiac arrests that occur in the US each year, more than 100,000 happen outside the home. Less than half (45.7%) of cardiac arrest victims get the immediate help they need before emergency responders arrive, in part because emergency medical services take, on average, between four and ten minutes to reach someone in cardiac arrest.

An international team of researchers looked at 49,555 out-of-hospital cardiac arrests that occurred in major US and Canadian cities. They analysed a key sub-group of these arrests, those that occurred in public, were witnessed and were shockable. The researchers found that nearly 66% of these victims survived to hospital discharge after a shock delivered by a bystander. Their findings emphasised that bystanders make a critical difference is assisting cardiac arrest victims before emergency responders can get to the scene.

Among the study’s results: bystanders used an AED in 18.8% of these cases; cardiac arrest victims who received a shock from a publicly-available AED had far greater chances of survival and being discharged from the hospital than those who did not; 66.5% versus 43%; cardiac arrest victims who received a shock from a publicly-available AED that was administered by a bystander had 2.62 times higher odds of survival to hospital discharge and 2.73 times more favourable outcomes for functioning compared to victims who first received an AED shock after emergency responders arrived; victims who received an AED shock from a bystander (57.1%) using a publicly-available device instead of having to wait for emergency responders (32.7%) had near normal function and better outcomes; and without a bystander using AED shock therapy, 70% of cardiac arrest patients either died or survived with impaired brain function.

“We estimate that about 1,700 lives are saved in the US per year by bystanders using an AED,” said senior study author Dr Myron Weisfeldt. “Unfortunately, not enough Americans know to look for AEDs in public locations, nor are they are trained on how to use them despite great and effective efforts of the American Heart Association.”

According to the AHA, use of an AED is the third step in the cardiac arrest chain of survival. The first two steps in a witnessed, out-of-hospital cardiac arrest are to 1) call 9-1-1 and 2) begin immediate cardiopulmonary resuscitation (CPR).

One of the study’s limitations is that it only examined bystander AED use without considering the combined impact of calling 9-1-1 and starting immediate CPR.

During a cardiac arrest, the electrical activity in the heart is disrupted. According to the AHA, every second counts because without immediate CPR, the heart, brain and other vital organs aren’t receiving enough oxygenated blood. For every minute without CPR, the chance of death increases by 10%.

Based on the study findings, Weisfeldt and his team, including lead author John Hopkins medical student Ross Pollack, would like to see greater distribution of AEDs, including equipping police with defibrillators, especially in regions where it takes emergency responders long to get to the patient. “Bystanders have the potential to save a life,” Weisfeldt continued. “This should be a great incentive for public health officials and bystanders to strive to have AEDs used on all victims of cardiac arrest.”

The AHA launched its Workplace Safety Training Initiative in 2017 with survey results that complement the Weisfeldt study’s insights. The Association’s survey found that most US employees are not prepared to handle cardiac emergencies in the workplace because they lack training in CPR and First Aid. In fact, half of all US workers (50%) cannot locate the AED at work. In the hospitality industry, that number rises to two-thirds (66%). More than 10,000 cardiac arrests occur annually in the workplace.

“First Aid, CPR and AED training need to become part of a larger culture of safety within workplaces,” said Dr Michael Kurz, chair of the AHA’s systems of care sub-committee and associate professor at the University of Alabama School of Medicine in the department of emergency medicine. “We are certainly seeing higher public interest in this training, and our campaign calls upon decision makers in workplaces and popular public spaces such as arenas, fitness centres, hotels, and churches to place AEDs in the same locations as a fire extinguisher.”

Background: Survival following out-of-hospital cardiac arrest (OHCA) with shockable rhythms can be improved with early defibrillation. Although shockable OHCA accounts for only ≈25% of overall arrests, ≈60% of public OHCAs are shockable, offering the possibility of restoring thousands of individuals to full recovery with early defibrillation by bystanders. We sought to determine the association of bystander automated external defibrillator use with survival and functional outcomes in shockable observed public OHCA.
Methods: From 2011 to 2015, the Resuscitation Outcomes Consortium prospectively collected detailed information on all cardiac arrests at 9 regional centers. The exposures were shock administration by a bystander-applied automated external defibrillator in comparison with initial defibrillation by emergency medical services. The primary outcome measure was discharge with normal or near-normal (favorable) functional status defined as a modified Rankin Score ≤2. Survival to hospital discharge was the secondary outcome measure.
Results: Among 49 555 OHCAs, 4115 (8.3%) observed public OHCAs were analyzed, of which 2500 (60.8%) were shockable. A bystander shock was applied in 18.8% of the shockable arrests. Patients shocked by a bystander were significantly more likely to survive to discharge (66.5% versus 43.0%) and be discharged with favorable functional outcome (57.1% versus 32.7%) than patients initially shocked by emergency medical services. After adjusting for known predictors of outcome, the odds ratio associated with a bystander shock was 2.62 (95% confidence interval, 2.07-3.31) for survival to hospital discharge and 2.73 (95% confidence interval, 2.17-3.44) for discharge with favorable functional outcome. The benefit of bystander shock increased progressively as emergency medical services response time became longer.
Conclusions: Bystander automated external defibrillator use before emergency medical services arrival in shockable observed public OHCA was associated with better survival and functional outcomes. Continued emphasis on public automated external defibrillator utilization programs may further improve outcomes of OHCA.

Ross A Pollack, Siobhan P Brown, Thomas Rea, Tom Aufderheide, David Barbic, Jason E Buick, James Christenson, Ahamed H Idris, Jamie Jasti, Michael Kampp, Peter Kudenchuk, Susanne May, Marc Muhr, Graham Nichol, Joseph P Ornato, George Sopko, Christian Vaillancourt, Laurie Morrison, Myron Weisfeldt

American Heart Association material
Circulation abstract

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