Minimally Interrupted Cardiac Resuscitation for Out-of-Hospital Cardiac Arrest

Summary and Comment |
March 11, 2008

Minimally Interrupted Cardiac Resuscitation for Out-of-Hospital Cardiac Arrest

  1. JoAnne M. Foody, MD

This new approach to cardiac resuscitation significantly improved survival rates in an observational study.

  1. JoAnne M. Foody, MD

Patients with out-of-hospital cardiac arrest have a dismal chance of survival. In this study, investigators sought to determine whether survival of such patients would improve with minimally interrupted cardiac resuscitation (MICR). This novel approach, aimed at maximizing cerebral perfusion, involves

  • an initial series of 200 uninterrupted chest compressions;

  • rhythm analysis, with a single defibrillator shock if indicated;

  • 200 immediate post-shock chest compressions before pulse check or rhythm reanalysis;

  • administration of epinephrine as soon as possible, repeated with each cycle of compressions and rhythm analysis;

  • delay of intubation until after three cycles of chest compression and rhythm analysis.

The researchers trained emergency medical services staff in two Arizona metropolitan areas to perform MICR. They then assessed records for patients with out-of-hospital cardiac arrest before and after the training. In a separate analysis that included data from 60 additional Arizona fire departments, they also compared outcomes in patients who received MICR according to the protocol with those in patients who did not. The main outcome of interest in both analyses was survival to hospital discharge.

A total of 886 patients with cardiac arrest from January 2005 through June 2007 were included in the two-city analysis. Survival to hospital discharge increased significantly, from 1.8% before MICR training to 5.4% after training (odds ratio, 3.0). In 174 patients with witnessed arrest and ventricular fibrillation, survival rates increased from 4.7% to 17.6% (OR, 8.6). The rate of compliance with the MICR protocol was 61%. In the larger analysis, involving 2460 patients with cardiac arrest between January 1, 2005, and November 22, 2007, survival to discharge was significantly better in patients who received MICR than in those who did not (9.1% vs. 3.8%; OR, 2.7).


Minimally interrupted cardiac resuscitation was associated with improved survival to hospital discharge in patients with out-of-hospital cardiac arrest. Encouraging as these results are, the study is limited by its observational design and by the possibility of the Hawthorne effect, whereby a short-term improvement is caused by observing worker performance. These findings are quite promising but need validation before being adopted into practice.


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