Bystanders Achieve Better Survival After CPR, AED for Cardiac Arrest vs EMS in Two Reports

Deborah Brauser

July 29, 2015

CHICAGO, IL — Two new studies add to previous research showing that early "bystander" interventions can improve outcomes after a witnessed out-of-hospital cardiac arrest, especially when compared with EMS-provided interventions.

The first study, which examined data on almost 5000 patients in North Carolina who had an out-of-hospital cardiac arrest, showed that survival to discharge was three times more likely after bystander-initiated cardiopulmonary resuscitation (CPR) and defibrillation vs interventions initiated by EMS[1]. Survival was also significantly higher after CPR was performed by bystanders and defibrillation performed by first responders (24.2%) and after CPR and defibrillation were performed just by first responders (25.2%) vs an EMS-initiated response (15.2%).

The study from Japan, which included data on more than 167,000 patients in Japan, echoed those findings. It showed significantly increased neurologically intact survival rates after bystander chest compression[2]. In addition, bystander-initiated defibrillation had twice the survival rates as defibrillation by EMS, and combined defibrillation by both bystanders and EMS had 1.5 times the survival rates as EMS-only defibrillation.

Lead author of the first study, Dr Carolina Malta Hansen (Duke Clinical Research Institute, Durham, NC) told heartwire from Medscape that the significant improvements occurring in such a short period of time was surprising.

"Overall, these were really remarkable results," she said. "We believe that pushing care forward, initiating care as fast as possible for cardiac-arrest patients in programs that enhance that, is likely to improve survival. And we believe our findings can inspire other communities to continue working on reducing time from cardiac arrest to initiation of care."

Both studies were published in the July 21, 2015 issue of the Journal of the American Medical Association.


Malta Hansen and colleagues assessed data for the years 2010-2013 from the Cardiac Arrest Registry to Enhance Survival (CARES) for 4961 patients.

During this time span, educational programs were launched throughout North Carolina through the Regional Approach to Cardiovascular Emergencies Cardiac Arrest Resuscitation System (RACE-CARS) to train the public in how to perform CPR and use automated external defibrillators (AEDs), as well to better train first responders after a cardiac arrest. First responders were defined as "dispatched police officers, firefighters, rescue squad, or life-saving crew trained to perform basic life support until arrival of the EMS."

"These initiatives differed from previous programs and focused on improving several of the links in the chain of survival for these patients, which are: recognize it's a cardiac arrest as fast as possible, call 911, initiate chest compression, defibrillate, and then provide advanced care," said Malta Hansen.

"Also, this program focused on urban as well as rural areas and everything in between and focused on improving care across all the different staff that are involved with a cardiac-arrest patient," she added. "Historically, these groups have worked in parallel and were very fragmented. This initiative was to bring people together to work as one team."

In 2010, bystander CPR after an out-of-hospital cardiac arrest was 39.3% and rose to 49.4% in 2013 (P<0.01). Bystander-initiated CPR and first-responder defibrillation together increased from 14.1%, to 23.1%, respectively (P <0.01). However, bystander-initiated defibrillation decreased slightly from 9.3% to 6.0%.

During this 3-year period, there was a significant increase in survival "with favorable neurological outcomes" for patients who received bystander CPR (from 7.1% to 9.7%, respectively, P=0.02).

Better Odds

Compared with EMS-performed CPR and defibrillation, the adjusted odds ratios (ORs) for survival to discharge was 3.12 (95% CI 1.78–5.46) after bystander CPR and defibrillation, 1.77 (95% CI 1.13–2.77) after first-responder CPR and defibrillation, and 1.70 (95% CI 1.06–2.71) after bystander CPR and first-responder defibrillation.

When asked if these findings might be because bystanders and first responders could provide these interventions faster than EMS, Malta Hansen said "that's difficult to say" because of the design of the study and its observational nature. "We can't say for sure why we saw this, so we can't confirm any causal relationship. However, we do know from previous studies designed around effectiveness of treatment that the faster you receive CPR and defibrillation, the higher the chance of survival."

She noted that the investigators now hope to examine whether certain groups benefit more than others from these initiatives or if some require more targeted interventions to improve outcomes. She is also currently working on assessing what factors or conditions empower bystanders to initiate these interventions, especially defibrillation. "We know little about how real-world bystanders perceive being in these situations."

In addition, Malta Hansen reported her association with a research group in Denmark, which will be starting a randomized controlled trial examining "the activation of trained lay rescuers in residential areas to be dispatched by emergency medical centers."

As reported by heartwire , two studies recently published in the New England Journal of Medicine introduced a program in Sweden where a smartphone positioning system dispatched CPR-trained volunteers to the area of a cardiac arrest, which significantly increased rates of bystander CPR.

Malta Hansen noted that she and the Denmark investigators have been in contact with the Swedish team "and hope to build on that" for their trial. "I'd also hope to do something similar in the US, but we need to clarify a number of issues first," she said. "There are many logistical issues that would need to be resolved, especially because the US has a more fragmented system than in Europe."

Survival Rates Improved, "but Quite Low"

In the second study, investigators led by Dr Shinji Nakahara (Teikyo University School of Medicine, Tokyo, Japan) examined records from the Utstein Registry database for 167,912 patients who experienced a witnessed out-of-hospital cardiac arrest between January 2005 and December 2012. The primary outcome of neurologically intact survival was measured using Glasgow-Pittsburgh Cerebral Performance Category scores.

A total of 23,797 bystander-witnessed cardiac arrests (18.7 per 100,000 persons) occurred in 2012, which was up from 17,882 (14.0 per 100,000 persons) in 2005.

Also increased between 2005 and 2012 were rates of bystander chest compressions (from 38.6% to 50.9%, respectively), bystander-only defibrillation (from 0.1% to 2.3%), and a combination of bystander and EMS defibrillation (from 0.1% to 1.4%). On the other hand, EMS-only defibrillation decreased from 26.6% to 23.5%.

Neurologically intact survival was significantly higher after bystander chest compressions (8.4%) were performed vs no bystander chest compression (4.1%, OR 1.52; 95% CI 1.45–1.60).

As for defibrillation, neurologically intact survival was significantly higher when performed by bystanders only (40.7%) vs EMS only (15.0%, OR 2.24; 95% CI 1.93–2.61). The OR for defibrillation from bystanders plus EMS was 1.50 (95% CI 1.31–1.71) vs EMS alone.

"The likelihood of neurologically intact survival improved but remained quite low," write the investigators. They note that, in addition to improved bystander interventions, increments of survival could have been associated with prehospital processes and with hospital and postresuscitation procedures, such as hypothermia. However, these factors were not evaluated.

"Necessary Component"

Dr Graham Nichol and Dr Francis Kim (both from University of Washington, Seattle) write in an accompanying editorial that out-of-hospital cardiac-arrest outcomes had not improved for more than 3 decades—until recently[3]. "It has become increasingly apparent that the involvement of bystanders is an important and necessary component" for this improvement, they write.

The editorialists point out that both of the current studies showed improvements after bystander CPR and "lay use" of an AED. However, the one by Malta Hansen examined et al only 11 counties in North Carolina, or just 30% of the state's population. So "there are some residual questions about the generalizability of the study results to other communities."

In the second study, "the improvement in outcomes associated with bystander CPR . . . reflects in part the large proportion of individuals with cardiac arrest who have a nonshockable rhythm and receive CPR but do not require defibrillation," write Nichol and Kim.

They note that additional, ongoing efforts are now needed to improve outcomes, including more efficient and better-coordinated care processes, increased training, and more funding for resuscitation research.

The first study was funded by the HeartRescue Project, which is funded by the Medtronic Foundation. Malta Hansen reported receiving grants from Laerdal, TryFonden, and Helsefonden. Disclosures for the coauthors are listed in the article. Nakahara and his coauthors have reported no relevant financial relationships. Nichol reports receiving grants from the National Heart, Lung, and Blood Institute; the US Food and Drug Administration; Cardiac Science; HeartSine Technologies; Philips Healthcare; Physio-Control; and Zoll and "other support" from Velomedix and Abiomed. Kim reports receiving support from Mallinckrodt Pharmaceuticals.


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