Despite technological advancement, globalization and an ever-growing evidence base which sculps the way prehospital care is delivered, there continues to be large gaps in some of the most critical areas that EMS is responsible for. Out-of-hospital cardiac arrest (OHCA) is a significant area of EMS responsibility, so much that the National Registry of Emergency Medical Technicians (NREMT) in the United States has historically required all its paramedics to possess and maintain valid Advanced Cardiac Life Support (ACLS) credentials every two years for its “traditional model of recertification.”1
So why do OHCA surveillance methods and published literature fail to transcend not only international boundaries, but also local and regional boundaries? We attempted to dig into this issue by conducting a narrative literature review to hopefully discover some of the challenges that currently face OHCA surveillance and hinder its epidemiological evidence base. We believe these challenges especially hinder OHCA researchers, but also prehospital patient care providers who are diligently attempting to keep up with best practices and the latest evidence in this field.
Cardiovascular disease is the number one killer in the world. In the U.S. it’s estimated that over 326,200 OHCA incidences occur annually.2 Despite health advancements and the ongoing practice of evidence-based medicine, OHCA continues to be a major public health burden. Survival to hospital discharge for OHCA has remained mostly unchanged for the past 30 years in most communities and regions.3 Although improvements have been made in select communities and regions, globally little to no improvements have been made.3 However, analytically studying OHCA trends across regional and national barriers can be challenging. We attempted to analyze this particular endeavor further.
Objectives & Methods
We had the following four objectives:
- Comparison of three case countries with different presumed profiles (U.S., United Arab Emirates (UAE), and Denmark regarding cardiac arrest registries/databases);
- To determine if internationally accepted Utstein guidelines for reporting OHCA were used or not;
- To find regional and international disparities in global OHCA reporting and outcomes; and
- To compare mortality after OHCA between the three countries.
We decided to conduct a narrative review where cardiac arrest registries/databases were published in English via the scholarly database MEDLINE at the U.S. National Library of Medicine National Institutes of Health were included.4 Keywords were selected based on the main subject matter and geographical location of case countries chosen. All available literature was searched, which appeared to contain information on out of hospital cardiac arrest, specifically related to registries, surveillance, population health, or disease burden challenges. OHCA data was captured and evaluated according to Utstein style core guidelines for uniform reporting of cardiac arrest.5
When comparing the OHCA data for the UAE, U.S., and Denmark some disparities were found. One of the most glaring differences come from UAE. The median ages of OHCA in Abu Dhabi and Dubai were 53 and 50 years, respectively.6,7 When compared to Denmark, the median age was reported between 68, and 72.8,9 Similarly, in the U.S. they were 66 to 64 in different registries.10,11 That’s a difference of around 20 years earlier for OHCA in UAE compared to Denmark and the U.S.
The Cardiac Arrest Registry to Enhance Survival (CARES) is the largest OHCA surveillance system in the U.S. It presented a mean age of 64, which is somewhat comparable to Denmark.9 Moreover, there was a large disparity in survival rates. The survival until discharge rate in UAE was reported as 3%.7 Meanwhile, in Denmark the 30-day survival in published papers were 10.8% nationally and 16% in a local study conducted in the Danish capital, Copenhagen.8,9 However, the annual reports from the Danish cardiac arrest registry aren’t published in English (only in Danish).
In the U.S., survival until discharge was 10.4% for CARES in 2017 and 10.6% for Resuscitation Outcomes Consortium.10,11 Again, UAE has a significant survival disparity for OHCA when compared to Denmark and the U.S. According to this preliminary data, someone who suffers a cardiac arrest outside of the hospital in Denmark and the U.S. has three times the chance of surviving compared to an OHCA victim in the United Arab Emirates. (See Figure 1.) All three countries show a gender disparity among males for cardiac arrest. In Dubai, over 82% of OHCA victims are male compared with Denmark, with reports in the mid-to-high 60% range. Meanwhile, the U.S. shows males suffering OHCA in the low 60 percentile range.6–11
Based on the literature above, people in UAE die up to 22 years earlier than people from Denmark and the U.S. from OHCA. Not only do they die 22 years earlier, but three times as many don’t survive their OHCA compared to Denmark and the U.S. In addition, more males suffer OHCA in UAE than in Denmark and the U.S.6–11
Assuming a common reference age of death as 75 years, one can gauge an estimate of the years of life lost to OHCA. Using a sample study from each case country above the years of life lost (YLL) for Denmark is 3, U.S. 7, and UAE 22 YLL. Although further research would be needed, this certainly eludes that a large disparity could exist.6–11
However, we feel the quantitative data and descriptive epidemiology above should merely serve as an interesting point of departure for further research, analysis and hypothesis formation. The process of trying to obtain this information and the shortcomings surrounding OHCA data we discovered, and which are described below, was our main finding within the time and scope of this literature review.
Cardiac Arrest Registries
“The best way to describe the epidemiology of a disease is to create a registry to which the disease is reported.”12 As mentioned earlier, one primary objective of this study was to identify, if Denmark, the U.S., and the UAE had OHCA registries. It was found that all three countries, at some level, participated in some form of national OHCA surveillance.
However, only one country, Denmark, had a national cardiac arrest database for the entire country.13 This registry included the entire nation and almost all OHCA incidents. Despite this, it’s difficult to find all desired information in English for Denmark’s cardiac arrest registry in the Medline database.
Furthermore, the official Danish cardiac arrest registry website is primarily in Danish and it was not possible to search it in English. Some studies in Medline were identified based on the Danish national cardiac arrest registry, such as the JAMA study mentioned below.8 However, the annual reports aren’t published in English, as opposed to CARES and the Resuscitation Outcomes Consortium (ROC), where the annual reports in English could be identified.
The U.S. provided many studies using its OHCA registry information during the Medline search, but coincidently fell short in other areas. The U.S. was found to use two major registries: ROC and CARES. The first problem is that instead of one central registry, the two separate entities cover different locations in the U.S. and part of Canada for OHCA surveillance. There was no indication from the literature reviewed that these two entities work together as one registry.
In addition to this, ROC only records information in main metropolitan areas which are selected by ROC to participate.14 ROC’s strategy excludes most of the U.S. geographically, especially rural America.
CARES and ROC each use different variables for reporting OHCA, creating further complications when evaluating a national burden. At the time of writing this article, none of the two U.S. registries report 30-day survival, but only survival to discharge. Timing of discharge can be influenced by local routines, whereas 30-day survival is an objective variable. Furthermore, it could be theorized that the regional surveillance strategy chosen creates a disparity among rural Americans and provides a challenge to national public health and global health programs.
UAE also faces many challenges with its registry. Only one out of the seven emirates in UAE have an ongoing OHCA surveillance program, and that registry/surveillance report wasn’t found on Medline. Instead, its results from the Pan-Asian Resuscitation Outcomes Study (PAROS) was identified.7 PAROS is the regional OHCA registry/surveillance system in which the UAE belongs. As a result, much of Abu Dhabi’s and Dubai’s OHCA outcome surveillance remains largely unknown. The remaining emirates have no published OHCA surveillance or reporting methods we could find in Medline.
Templates & Variables
Finding literature with the same set of variables was a major challenge within the time and scope of this review. This further supports our theory that this is a major challenge when assessing OHCA across regional or national borders. Although this was a barrier, it helps solidify the fact that a common set of international guidelines needs to be utilized to a much greater extent in the scientific literature surrounding OHCA. We believe this is one great disparity which was unveiled. Even variables as simple as “age” were often not reported in the same way.6,15,16
Utstein reporting is the international standard but is often not used by OHCA registries and in OHCA published literature. However, it’s also worth noting that Utstein reporting format changes regularly with updates and that the Utstein format from 10 years ago isn’t the same as the 2015 standard. To try and help combat this issue Utstein “core variables” were used and “optional variables” were excluded to encompass more literature and make for easier comparison. Despite this, it was still complicated to find studies which matched and reported variables uniformly.
Healthcare providers, health officials and others interested in OHCA who are searching to evaluate the burden of OHCA at a regional or global level will be bombarded with a plethora of scientific papers in Medline alone. Locating and analyzing uniform OHCA data can prove a challenge to many interested parties who search for literature in this area and aren’t experts in resuscitation research. Most of the papers located and screened in the literature search conducted for this narrative review did not provide up to date uniform Utstein templates.
International variation in the reporting of OHCA, including which models and variables are used in registries and published literature is an ongoing problem. These differences in the way that OHCA is measured and defined continue to plague the international community and OHCA literature, despite international recommendations.17
Although the Utstein template has been discussed in this review as the recommended international template, it should be noted that it’s not without its limitations. Utstein guidelines have been criticized for lacking empirical evidence, and that other reporting method could be more efficient.17
Despite its limitations, the global community needs a reference point and measuring tool for OHCA. No common theme, structure, template or operationalization of variables existed across much of the literature reviewed. This makes synthesizing the literature for evaluating the global burden of OHCA incredibly challenging and time-consuming and likely beyond the scope of this review.
Furthermore, various registries have different inclusion and exclusion criteria. To be included into the CARES registry, patients suffering an OHCA must be of presumed cardiac etiology and have received some form of resuscitation effort by bystanders or health care personnel.11 Patients with obvious signs of death, such as rigor mortis aren’t considered for admission into the registry. Patients who have an advanced directive such as a do not resuscitate (DNR) order are also excluded from the registry. A Danish publication using national data included clinical conditions of cardiac arrest that resulted in resuscitation efforts excluding obvious late signs of death (e.g., rigor mortis) for which resuscitative efforts were not initiated.8 In PAROS, for UAE, patients with obvious late signs of death were also excluded; however, “All OHCA cases (including both children and adults) of presumed cardiac and non-cardiac etiology conveyed by EMS or presenting at EDs, were captured in the study,” which is contrast to much of the other literature we reviewed.7
Discussion & Future Considerations
EMS systems and prehospital care providers could—and should, arguably—help establish, maintain, and contribute to OHCA surveillance, cardiac arrest registries and OHCA research. This branch of the healthcare system is on the front line, because OHCA takes place in the prehospital environment.
EMS leaders and prehospital care providers alike can work with local stakeholders, health authorities, and national and international bodies to help improve OHCA surveillance and research in their region. Examples of this include establishing cardiac arrest registries that are linked with the national or regional OHCA monitoring; ensuring international uniform reporting standards; and helping to achieve OHCA data sharing between different EMS agencies, hospitals, public health officials and global health programs. Together, they can significantly contribute to OHCA surveillance and evaluate the global burden of OHCA. Something as simple as linking data or data sharing between prehospital and in-hospital is still an ongoing challenge in the countries and environments that were reviewed.6,18
UAE had some unique findings for a high-income country. However, one could speculate that some of these results could be because of its interesting demography. For example, the population in Dubai consists of about 233,430 residents that were Emirati locals and 2,465,170 who were non-Emirati.19
UAE is known to have a large and dynamic expatriate workforce, and it can be challenging to find the official statistics for this information, but the UAE government shows that local Emiratis are the minority of country’s population, and the majority living in UAE are expatriates.20 Some non-governmental organizations indicate that the foreign population of UAE is 7.8 million out of its total population of 9.2 million residents. The majority of these people are from low- and middle-income countries such as Bangladesh, Pakistan, and India and are temporary labor.21 Therefore, it can be speculated that UAE’s OHCA statistics are difficult to compare with the U.S. and Denmark. It’s unclear how this effects the OHCA results reviewed, but further research in this area would be very interesting.
Large disparities exist surrounding OHCA patients among three different high-income countries. In addition to this, there are significant gaps in capturing, reporting, sharing and analyzing OHCA data across regional and national borders. Uniformity of reporting standards continue to hinder the epidemiological evidence base for OHCA. Much about OHCA epidemiology is still unknown in many regions of the world, including countries with regional OHCA surveillance in place. These findings present considerable challenges not only nationally, but globally for evaluating the global burden of out-of-hospital cardiac arrest.
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