title: Delayed versus immediate defibrillation for out-of-hospital cardiac arrest due to ventricular fibrillation: A systematic review and meta-analysis of randomised controlled trials.
abstract: BACKGROUND
  Human studies over the last decade have indicated that delaying initial defibrillation to allow a short period of cardiopulmonary resuscitation (CPR) may promote a more responsive myocardial state that is more likely to respond to defibrillation and result in increased rates of restoration of spontaneous circulation (ROSC) and/or survival. Out-of-hospital studies have produced conflicting results regarding the benefits of CPR prior to defibrillation in relation to survival to hospital discharge. The aim of this study was to conduct a systematic review and meta-analysis of randomised controlled trials comparing the effect of delayed defibrillation preceded by CPR with immediate defibrillation on survival to hospital discharge.
  
  
  METHODS
  A systematic literature search of key electronic databases including Medline, EMBASE, and the Cochrane Library was conducted independently by two reviewers. Randomised controlled trials meeting the eligibility criteria were critically appraised according to the Cochrane Group recommended methodology. Meta-analyses were conducted for the outcomes of survival to hospital discharge overall and according to response time of emergency medical services.
  
  
  RESULTS
  Three randomised controlled trials were identified which addressed the question of interest. All included studies were methodologically appropriate to include in a meta-analysis. Pooled results from the three studies demonstrated no benefit from providing CPR prior to defibrillation compared to immediate defibrillation for survival to hospital discharge (OR 0.94 95% CI 0.46-1.94). Meta-analysis of results according to ambulance response time (</=5min or >5min) also showed no difference in survival rates.
  
  
  CONCLUSIONS
  Delaying initial defibrillation to allow a short period of CPR in out-of-hospital cardiac arrest due to VF demonstrated no benefit over immediate defibrillation for survival to hospital discharge irrespective of response time. There is no evidence that CPR before defibrillation is harmful. Based on the existing evidence, EMS jurisdictions are justified continuing with current practice using either defibrillation strategy.
authors.affiliation: Ambulance Research Institute, Ambulance Service of New South Wales, Locked Bag 105, Rozelle, Sydney, NSW 2039, Australia. psimpson@ambulance.nsw.gov.au
authors.forename: Paul M
authors.initials: PM
authors.lastname: Simpson
authors.forename: Mark S
authors.initials: MS
authors.lastname: Goodger
authors.forename: Jason C
authors.initials: JC
authors.lastname: Bendall
mesh_terms: D004554:Electric Countershock / Q000379:methods*; D004632:Emergency Medical Services / Q000379:methods*; D006323:Heart Arrest / Q000209:etiology / Q000628:therapy*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000150:complications* / Q000503:physiopathology / Q000628:therapy