Clinical question: How does a brief period of CPR with early analysis of rhythm compare with the strategy of a longer period of CPR with delayed analysis of rhythm in patients with out-of-hospital cardiac arrest?
Background: Based on current guidelines, emergency medical service (EMS) personnel could provide two minutes of CPR before the first analysis of cardiac rhythm. However, there is a paucity of data on the outcomes of this strategy versus the short CPR and early rhythm analysis.
Study design: The EMS groups participating in the study were cluster-randomized to one strategy or the other.
Settings: The Resuscitation Outcome Consortium (ROC) is a clinical trial consortium comprising 10 U.S. and Canadian universities and their regional EMS systems. The trial was conducted at 150 of the 260 EMS agencies participating in the ROC.
Synopsis: This is a cluster-randomized trial involving adults with out-of-hospital cardiac arrest. Patients in the early-analysis group were assigned to receive 30 to 60 seconds of EMS-administered CPR, and those in the later-analysis group were assigned to receive 180 seconds of CPR, before the initial electrocardiographic analysis. The primary outcome was survival to hospital discharge with satisfactory functional status (a modified Rankin scale score of =3, on a scale of 0 to 6, with higher scores indicating greater disability).
The study included 9,933 patients, of whom 5,290 were assigned to early analysis of cardiac rhythm and 4,643 to later analysis. A total of 273 patients (5.9%) in the later-analysis group and 310 patients (5.9%) in the early-analysis group met the criteria for the primary outcome, with a cluster-adjusted difference of -0.2 percentage points (95% confidence interval, -1.1 to 0.7; P=0.59).
Analyses of the data with adjustment for confounding factors, as well as subgroup analyses, showed no survival benefit for either study group.
Bottom line: Among patients who had an out-of-hospital cardiac arrest, there is no difference in the outcomes with a brief period, as compared with a longer period, of EMS-administered CPR before the first analysis of cardiac rhythm.
Citation: Stiell IG, Nichol G, Leroux BG, et al. Early versus later rhythm analysis in patients with out-of-hospital cardiac arrest. N Engl J Med. 2011;365;787-797.
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