Review articleSingle-shock defibrillation success in adult cardiac arrest: A systematic review☆
Introduction
One of the critical links in the Chain of Survival is rapid defibrillation [1]. With every minute that passes between collapse and defibrillation, survival rates from witnessed ventricular fibrillation (VF) sudden cardiac arrests (SCA) decrease by 7–10% if no cardiopulmonary resuscitation (CPR) is provided and 3–4% if bystander CPR is provided [2], [3], [4], [5]. Thus, early defibrillation remains the first line therapy for VF and pulseless ventricular tachycardia (VT).
Another critical component to successful CPR is minimizing the time without chest compressions (no flow time [NFT]). Recently, there has been a focus on strategies to reduce NFT during CPR and external defibrillation [6], [7], [8]. Two prospective before-and-after studies have shown that there is a significant survival benefit associated with a single-shock defibrillation protocol compared with a three-stacked-shock protocol [9], [10]. As a result, the 2010 CPR guidelines have recommended a single-shock protocol [11]; however, the international consensus on science statement and treatment recommendations for 2010 suggested that first-shock efficacy across different waveforms remains an important scientific knowledge gap [12].
Defibrillators are available in various waveforms: monophasic waveforms, which include monophasic damped sinusoidal (MDS) waveforms and monophasic truncated exponential (MTE) waveforms, as well as biphasic waveforms, which include biphasic truncated exponential (BTE) waveforms and rectilinear biphasic (RLB) waveforms. Although there is a consensus that biphasic waveforms are more effective than monophasic waveforms when delivered as three stacked shocks [11], there has yet to be a definitive trial or systematic review and systematic meta-analysis on one-shock defibrillation success across all monophasic and biphasic waveforms. Additionally, the optimal energy for first-shock success has not been determined. The objective of this paper is to conduct a systematic review and meta-analysis of randomized controlled trials of first-shock success in defibrillation of out-of-hospital cardiac arrests, across all waveforms and energy levels.
Section snippets
Methods
MEDLINE (1948 to May 2011, updated to June 2012), EMBASE (1947 to May 2011, updated to June 2012), EBM Reviews (Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Cochrane Methodology Register, and Health Technology Assessment), dissertation and thesis abstracts, Web of Science Conference Proceedings and clinicaltrials.gov were all searched from conception to May 2011 (updated to June 2012) using medical subject
Literature search
Of the 3281 potentially relevant citations obtained in the initial literature search, eight papers [14], [15], [16], [17], [18], [19], [20], [21] reporting results from six randomized clinical trials on first-shock success in adult cardiac arrest were identified as eligible for this review. These papers had weighted Kappa statistics of 0.53, 0.71, and 0.94, respectively for title, abstract and full article hierarchal review (Fig. 2, Table 2). In addition, the ORBIT investigators provided
Discussion
Across all waveforms, energy levels, and measures of shock success, biphasic waveforms out-performed monophasic with little variability in first-shock success, by any outcome. Our initial intention was to determine a statistically relevant pooled value for first-shock success between waveforms and energy levels; however, this was abandoned when the raw data were reviewed. Only the ORBIT study [14] used the RLB waveform and only the Schneider study [18] used the ICBTE waveform and it would be
Limitations
Due to low study and participant numbers and a lack of variability for two waveforms, we were not able to pool the results and provide a statistical comparison between waveforms and energy levels. In addition, we were unable to perform a priori sensitivity analyses for automatic external defibrillator versus manual defibrillator, randomization at the first responder versus advanced life support level of responder, and short versus long median response time intervals.
Conclusions
Biphasic waveforms are uniformly more effective in terms of first-shock success than monophasic across energy levels in a stacked-shock protocol. Given that the first-shock success is not significantly different across defibrillator waveforms and energy levels, it is likely that all biphasic defibrillators have similar clinical efficacy. Further research should address the need for escalating energy levels given the switch to a single-shock strategy and other changes in resuscitation practice
Conflict of interest statement
Dr. Laurie Morrison has career support from the United States National Institute of Health (NIH), through the Resuscitation Outcomes Consortium, and has active peer-reviewed research grants in this content area from the Canadian Institutes of Health Research (CIHR), NIH and the Heart and Stroke Foundation of Canada. Defibrillator companies (ZOLL Medical Corporation, Medtronic and Laerdal [Philips]) have offered in-kind donations for equipment to all the Emergency Medical Services and Fire
Acknowledgements
Funding sources: This study was funded by the Keenan Research Centre, Li Ka Shing Knowledge Institute Summer Student Scholarship Program and Rescu, Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital. These funding sources were not involved in any part of this systematic review.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2013.07.008.