title: Resuscitation Outcomes Consortium (ROC) PRIMED cardiac arrest trial methods part 2: rationale and methodology for "Analyze Later vs. Analyze Early" protocol.
abstract: OBJECTIVE
  The primary objective of the trial is to compare survival to hospital discharge with modified Rankin score (MRS) < or =3 between a strategy that prioritizes a specified period of CPR before rhythm analysis (Analyze Later) versus a strategy of minimal CPR followed by early rhythm analysis (Analyze Early) in patients with out-of-hospital cardiac arrest.
  
  
  METHODS
  Design-Cluster randomized trial with cluster units defined by geographic region, or monitor/defibrillator machine. Population-Adults treated by emergency medical service (EMS) providers for non-traumatic out-of-hospital cardiac arrest not witnessed by EMS. Setting-EMS systems participating in the Resuscitation Outcomes Consortium and agreeing to cluster randomization to the Analyze Later versus Analyze Early intervention in a crossover fashion. Sample size-Based on a two-sided significance level of 0.05, a maximum of 13,239 evaluable patients will allow statistical power of 0.996 to detect a hypothesized improvement in the probability of survival to discharge with MRS < or =3 rate from 5.41% after Analyze Early to 7.45% after Analyze Later (2.04% absolute increase in primary outcome).
  
  
  CONCLUSIONS
  If this trial demonstrates a significant improvement in survival with a strategy of Analyze Later, it is estimated that 4000 premature deaths from cardiac arrest would be averted annually in North America alone.
authors.affiliation: Ottawa, Ontario, Canada. istiell@ohri.ca
authors.forename: Ian G
authors.initials: IG
authors.lastname: Stiell
authors.forename: Clif
authors.initials: C
authors.lastname: Callaway
authors.forename: Dan
authors.initials: D
authors.lastname: Davis
authors.forename: Tom
authors.initials: T
authors.lastname: Terndrup
authors.forename: Judy
authors.initials: J
authors.lastname: Powell
authors.forename: Andrea
authors.initials: A
authors.lastname: Cook
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kudenchuk
authors.forename: Mohamud
authors.initials: M
authors.lastname: Daya
authors.forename: Richard
authors.initials: R
authors.lastname: Kerber
authors.forename: Ahamed
authors.initials: A
authors.lastname: Idris
authors.forename: Laurie J
authors.initials: LJ
authors.lastname: Morrison
authors.forename: Tom
authors.initials: T
authors.lastname: Aufderheide
mesh_terms: D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D016000:Cluster Analysis; D018592:Cross-Over Studies; D003625:Data Collection / Q000379:methods; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D004632:Emergency Medical Services / Q000458:organization & administration*; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D010043:Outcome and Process Assessment, Health Care; D010351:Patient Discharge / Q000706:statistics & numerical data*; D012107:Research Design; D016037:Single-Blind Method; D015996:Survival Rate; D013997:Time Factors