The theory that a more perfused heart will respond better to defibrillation shock makes intuitive sense. However Ian G. Stiell, MD, and colleagues found no difference in outcomes when comparing patients who received CPR by EMS providers for 30—60 seconds for “early” defibrillation to a second group that received CPR for 180 seconds of CPR for “late” defibrillation.
The cluster-randomized study was conducted at 10 ROC sites in the U.S. and Canada on 9,933 patients with non-traumatic out-of-hospital cardiac arrest that had not been witnessed by EMS personnel.
Survival-to-hospital discharge with a modified Rankin score of three or less–considered satisfactory neurological function–was 5.9% for both groups. In addition, the researchers reported that there was no significant difference between the study groups with respect to any of the secondary outcomes.
The participating agencies were already “high-functioning” services with advanced-level paramedics. To reinforce proper techniques, the EMS personnel received study-specific instruction every six months that emphasized uninterrupted compressions and ventilations at a ratio of 30:2. Yet “the duration of CPR before the first analysis of rhythm did not fall within the assigned target for 36% of the patients.”The authors concluded that this represents the degree of precision with which such therapies are likely to be practiced within the limitations of the out-of-hospital environment.
Conclusion: No difference in the outcome between the EMS strategy of a brief period of CPR before early rhythm analysis and that of a longer period of CPR before delayed rhythm analysis.
Reference
- 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 Sep 1; 365:787. doi:10.1056/NEJMoa1010076
