Resuscitation Outcomes Consortium (ROC) PRIMED cardiac arrest trial methods : Part 2: Rationale and methodology for “Analyze Later vs. Analyze Early” protocol

SummaryObjectiveThe primary objective of the trial is to compare survival to hospital discharge with modified Rankin score (MRS) ≤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.MethodsDesign—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 ≤3 rate from 5.41% after Analyze Early to 7.45% after Analyze Later (2.04% absolute increase in primary outcome).ConclusionIf 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.