Current Events in Cardiac Arrest Research

It is important for EMS providers to not only be up to date on cardiac arrest standards, but also to understand the studies underpinning them

Ever since the first care report of successful modern CPR was published in 1960, research aimed at refining it has grown exponentially.1 Early AHA guidelines for ACLS, in 1974, were quite different than current ones, although many core components have persisted.2, 3 Even across recent years, standards of care have changed dramatically; it wasn’t long ago that capnography was relatively unknown to EMS and placing the tube was priority number one. At present, the AHA guidelines are updated every five years, most recently in 2010. Guideline changes are based on a literature review performed by experts in various fields across the world, a process that has already begun for the 2015 update. The International Liaison Committee on Resuscitation (ILCOR) is the coordinating body that sifts through reviewers’ recommendations and proposes changes. As the frontline providers in cardiac arrest care, it is important for EMS providers to not only be up to date on cardiac arrest standards, but also to understand the studies underpinning them. This article reviews recent literature that may soon change the way you care for your most ill patients.

Medication Use in Cardiac Arrest

It has been more than 10 years since bretylium, isoproterenol and high-dose epinephrine were questioned for their usefulness in cardiac arrest, and removed from both the guidelines and ambulances.4 More recently, in 2005, lidocaine was largely replaced by amiodarone.5 Only two years ago, with the 2010 changes, was atropine removed.6 Today, standard epinephrine, vasopressin and even the antiarrhythmics are being questioned in large research trials. A recent editorial in the Journal of the American Medical Association (JAMA) claimed, “The best available observational evidence indicates that epinephrine may be harmful to patients during cardiac arrest, and there are plausible biological reasons to support this.”7

Epinephrine, long considered a core component of cardiac arrest management, has never been properly studied for effectiveness. In fact, neither have most of the cardiac arrest medications until recently. It was only in 2003 that a group of researchers in Norway decided to evaluate medication effectiveness in a six-year randomized trial in which patients received either a normal regimen of IV drugs by paramedics or none. The results were surprising: although return of spontaneous circulation (ROSC) rates were improved (32% in the control group receiving normal medications vs. 21% in the trial group receiving placebo), there was no change in all other outcomes. These other outcomes included survival to discharge, favorable neurological outcome and one-year survival.8 These results raised an important question that healthcare providers are obligated to consider: What is considered good outcome? Is more ROSC really a good thing when survival to discharge and neurological outcome are unchanged? Put in a population-based context, this question becomes: Is this the best use of healthcare resources?

In 2006, a group in Western Australia performed a randomized trial that put epinephrine against placebo. Similar to the Norway study, paramedics gave either real epinephrine or placebo to cardiac arrest patients without knowing which was which—a “blinded” study. This study again showed a higher ROSC in the epinephrine group (23.5%) than the placebo group (8.4%). However, this study also showed there was no statistically significant change in survival to discharge, prompting the same questions as the previous study.9 Difficulties with the execution of this study highlighted some important issues for EMS providers to consider as our field becomes increasingly research-driven and evidence-based. Although planned as a multicenter study to include a larger number of patients, four out of five EMS services refused to participate as they felt it unethical to “withhold the standard of care,” meaning epinephrine. As EMS providers we need to decide what is truly unethical: that, or relying on an unproven medication, which may not help or may even harm patients, simply because “that’s how it’s always been done.” The lack of agency participation and negative press led to this study being halted early. As the authors of this study put it, barriers to research such as this “serve only to ensure such interventions remain unproven.”

This content continues onto the next page...