title: Single-shock defibrillation success in adult cardiac arrest: a systematic review.
abstract: OBJECTIVE
  Current resuscitation guidelines advise a single biphasic shock followed by chest compressions; however, it is unclear if this applies to all waveforms and energy levels. We conducted a systematic review of the literature to determine the comparative success rates for single-shock defibrillation across waveforms evaluated in out-of-hospital cardiac arrest patients.
  
  
  METHODS
  EMBASE, MEDLINE, EBM Reviews, dissertation abstract databases, and clinicaltrials.gov were searched. Two investigators independently reviewed titles, abstracts and full texts in a hierarchical manner for study eligibility with a quadratic kappa score at each level. Two authors abstracted data independently and the quality of the articles was assessed using the five-point Jadad scale. Outcomes were termination of ventricular fibrillation (VF)/ventricular tachycardia (VT) at 5s post shock (TOF), return of organized rhythm (ROOR) and return of spontaneous circulation (ROSC).
  
  
  RESULTS
  A total of 3281 potentially relevant citations were identified and, of these, eight papers were selected with Kappa values of 0.53 for titles, 0.71 for abstracts, and 0.94 for articles. Quality scores varied from 0 to 4/5. Biphasic first-shock success for all three outcomes of interest was similar regardless of energy levels, and uniformly superior to monophasic first-shock success. Median time to first shock varied across trials based on level of randomization (first responders versus advanced life support tiered response) and may contribute to observed differences. Lack of variability across two waveforms precluded a meta-analytical approach.
  
  
  CONCLUSIONS
  This systematic review suggests that evaluated biphasic waveforms have similar first-shock success as measured by the three outcomes of interest and all are superior to monophasic shocks.
authors.affiliation: Rescu, Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada; Division of Emergency Medicine, University of Toronto, Toronto, Ontario, Canada. Electronic address: MorrisonL@smh.ca.
authors.forename: Laurie J
authors.initials: LJ
authors.lastname: Morrison
authors.forename: Rowan M
authors.initials: RM
authors.lastname: Henry
authors.forename: Vivien
authors.initials: V
authors.lastname: Ku
authors.forename: Jerry P
authors.initials: JP
authors.lastname: Nolan
authors.forename: Peter
authors.initials: P
authors.lastname: Morley
authors.forename: Charles D
authors.initials: CD
authors.lastname: Deakin
mesh_terms: D000328:Adult; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy*; D006336:Heart Massage; D006801:Humans
keywords: Cardiac arrest; Defibrillation; Defibrillator waveforms; Ventricular fibrillation