Since prehospital emergency medical services has been around for 40 years you’d think we’d have lots of data on the survival experience of hundreds and hundreds of communities. Yet such information does not exist. A 2005 review of the scientific literature identified only 35 US communities (representing 9% of the US population) that reported their cardiac arrest experience (Rea TD, Eisenberg MS, Sinibaldi G, White RD. Incidence of EMS-treated out-of-hospital cardiac arrest in the United States. Resuscitation 2004;63:17-24.). Overall the survival rate for all treated cardiac arrests was 8%, and for patients with ventricular fibrillation the rate was 18%. Using these figures and projecting to the entire US population the study estimated that approximately 13,000 Americans are discharged every year following cardiac arrest. (Just imagine if the national survival rate for VF was 36%. There would be an additional 13,000 individuals surviving every year.)
There are complex reasons why so few communities report their survival rates. Perhaps the biggest reason is simply a lack of resources. Many small communities can barely pay EMS staff let alone devote time and resources to gathering information on cardiac arrest survival. The problem is compounded by hospitals that invoke HIPAA (privacy laws) and refuse to provide discharge information to outside agencies (in fact there are ample opportunities for hospitals to release this information when it is requested as part of a quality assurance program and when confidentiality safeguards are in place). Furthermore, there are no state or national mandates for communities to report their cardiac arrest experience. Many communities may report a figure but this is often an estimate and not rigorously measured. To be valid, a community must collect information in a specific fashion and agree to common definitions. Finally, another possible reason is the “shame” factor. The community realizes how few patients are saved and is simply “embarrassed” to broadcast this information to the world. I have great respect for the researchers in New York, Chicago, Los Angeles, and Detroit who had the courage to document and publish the underwhelming performance. The Chicago article led to several concrete steps including four new paramedic units and renewed training. However, no follow-up was performed to see if the situation improved, and it has been 16 years since the study was published.
The effect of different definitions on survival rates is readily apparent from a 1991 King County study. The study reports rates of survival ranging from 16% to 49% depending on definitions of what patients comprise the denominator. (Eisenberg MS, Cummins RO, Larsen MP. Numerators, denominators, and survival rates: reporting survival from out-of-hospital cardiac arrest. Am J Emerg Med 1991;9:544-6.) For example, when all the cardiac arrests from all the causes are included the survival (hospital discharge) rate is 16%. But if only witnessed collapse cases due to underlying heart disease with an onset of CPR of 4 minutes or less and definitive care of less than 8 minutes are included then the survival jumps to 49%. Same community, different survival rates. It’s magic! Just change the definition and one triples the survival rate. This is why trying to draw cross-community comparisons when all parties do not agree on the definitions is like attempting to organize a tournament when each team plays by its own rules. A community, determined to be number one in cardiac arrest survival, could simply define its cases as patients with witnessed cardiac arrests in VF, who have bystander CPR, who respond to one shock with a perfusing rhythm (good blood pressure and pulse), and who wonder what’s for dinner upon arrival in the coronary care unit. Such a denominator might result in a survival rate close to 100% yet such a figure would be silly and meaningless.
The chaos of definitions was widely recognized and led to a major international meeting held in the Utstein Abbey just outside Stavanger, Norway in 1991. The resulting criteria, known as the Utstein Criteria, established a set of common definitions and spelled out exactly how to report cardiac arrest data. It was hoped that the criteria would serve as a tool to facilitate EMS leaders and researchers as they sought to understand the reasons for different survival rates among communities. (Cummins RO, Chamberlain DA, Abramson NS, et al. Recommended guidelines for uniform reporting of data from out-of-hospital cardiac arrest: the Utstein Style. A statement for health professionals from a task force of the American Heart Association, the European Resuscitation Council, the Heart and Stroke Foundation of Canada, and the Australian Resuscitation Council. Circulation 1991;84:960-75).
The criteria were revised in 2004 with further clarification of the definitions and the required data elements. (Jacobs I, Nadkarni V, Bahr J, et al. Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries. A statement for healthcare professionals from a task force of the international liaison committee on resuscitation (American Heart Association, European Resuscitation Council, Australian Resuscitation Council, New Zealand Resuscitation) Despite this effort to create a consistent case definition (“a witnessed cardiac arrest due to presumed underlying heart disease with the initial rhythm of ventricular fibrillation”), few communities are able (or willing) to use the criteria to publish accurate survival figures.