Emergency medical services/original researchPredicting Survival After Out-of-Hospital Cardiac Arrest: Role of the Utstein Data Elements
Introduction
Out-of-hospital cardiac arrest claims hundreds of thousands of lives each year in North America.1 Hence, improving survival from cardiac arrest provides a meaningful opportunity to improve public health. For example, survival after ventricular fibrillation cardiac arrest ranges from 3% to more than 40%, depending on the community. Such variability suggests the potential to save thousands of additional lives if we can fully understand patient, circumstance, or care characteristics that critically influence prognosis.2, 3 This appreciation has produced the framework of resuscitation care termed “the links in the chain of survival,” which include early emergency activation, early cardiopulmonary resuscitation (CPR), early defibrillation, and timely and appropriate advanced care.4 Guidelines have provided core measures designed to assess the links in the chain of survival. These measures, termed the Utstein data elements, provide the basis for evaluating and comparing care and outcomes within and across communities.5
The extent to which these Utstein measures predict survival and account for outcome differences is not well studied. If such measures incompletely predict survival, the implications are that other unmeasured patient, circumstance, or care characteristics importantly influence resuscitation outcomes and would indicate a need for additional investigation to identify and measure outcome predictors.6 This understanding can, in turn, directly guide efforts to improve resuscitation.
We used data from the Resuscitation Outcomes Consortium Epistry–Cardiac Arrest, an observational epidemiologic registry of out-of-hospital cardiac arrests, to determine the extent to which the Utstein data elements predict survival after out-of-hospital cardiac arrest and whether these data elements account for survival differences across participating Resuscitation Outcomes Consortium sites overall and among the clinical subset with bystander-witnessed ventricular fibrillation.7 We specifically focused on this latter clinical subset, given that each of the Utstein elements can influence outcome in bystander-witnessed ventricular fibrillation or ventricular tachycardia. Hence, this clinical subset is the most relevant group designed to compare and contrast system performance.5 We hypothesized that the Utstein data elements predict survival to hospital discharge but explain only a portion of survival variation overall and across sites participating in the Resuscitation Outcomes Consortium.
Section snippets
Study Design, Setting, and Selection of Participants
This investigation is an observational, prospective data collection, case series of all persons older than 20 years and with nontraumatic out-of-hospital cardiac arrest from December 1, 2005, through March 1, 2007, who received attempted resuscitation (treatment) by organized emergency medical services (EMS) among 7 sites participating in the Resuscitation Outcomes Consortium. The Resuscitation Outcomes Consortium is an out-of-hospital emergency care clinical trials network composed of 11 sites
Results
During the 16 months of observation, 10,681 persons experienced cardiac arrest and received attempted EMS resuscitation (Figure 1). Of these, 23.0% (2,456/10,681) presented with an initial rhythm of ventricular fibrillation or ventricular tachycardia, and 13.7% (1,459/10,681) were citizen bystander–witnessed ventricular fibrillation or ventricular tachycardia arrest because of presumed cardiac cause. A total of 9.5% (1,013/10,681) of all EMS-treated arrests and 3.2% (47/1,459) of
Limitations
This investigation has important limitations. Information was not available about hospital care of these patients. Some of the unexplained outcome variation may be due to differences in hospital-based treatments such as induced hypothermia, which can affect survival.14, 15, 16 Although the current study is a prospective investigation that used uniform data definitions, misclassification of data elements may still have occurred. Moreover, 10% of cases had missing covariate data (3% of the
Discussion
In this large, multisite study of EMS-treated out-of-hospital cardiac arrest, the Utstein data elements predicted survival but accounted for only a portion of the outcome variability among all EMS-treated arrests and the subset with bystander-witnessed ventricular fibrillation arrests or ventricular tachycardia because of presumed cardiac cause. Although Utstein data elements predict survival overall and within sites, they account for only a modest portion of survival differences between sites.
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Supervising editor: Amy H. Kaji, MD, PhD, MPH
Author contributions: TDR conceived the study. TDR and AJC designed the study. TDR, IGS, JP, BB, CWC, SC, TPA, LM, TET, TB, LW, DD, AI, and GN were responsible for data collection. AJC, JP, and GN managed the data. AJC provided statistical advice on study design and analyzed the data. TDR drafted the article, and all authors contributed substantially to its revision. TDR takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. This study was supported by a series of cooperative agreements to 10 regional centers and 1 data coordinating center (5U01 HL077863, HL077881, HL077871, HL077872, HL077866, HL077908, HL077867, HL077885, HL077887, HL077873, HL077865) with the National Heart, Lung, and Blood Institute, in partnership with the National Institute of Neurological Disorders and Stroke, US Army Research and Materiel Command, The Canadian Institutes of Health Research-Institute of Circulatory and Respiratory Health, Defense Research and Development Canada, American Heart Association, and the Heart and Stroke Foundation of Canada.
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Publication date: Available online November 27, 2009.