Clinical paperThe effect of time to defibrillation and targeted temperature management on functional survival after out-of-hospital cardiac arrest☆
Section snippets
Background/introduction
Every year in North America, there are over 400,000 out-of-hospital cardiac arrests (OHCA) with a survival rate of 5–10%.1, 2 The probability of survival from OHCA decreases from the time of collapse to emergency medical service (EMS) intervention, however, the exact relationship between time and survival is not known. It has been proposed that cardiac arrests transition through three distinct phases of pathophysiology: electrical phase (<4 min), circulatory phase (4–10 min) and metabolic phase
Study design
This was a retrospective, observational study using data from the Toronto Regional RescuNet Epistry database, based upon the Resuscitation Outcomes Consortium (ROC) Epistry-Cardiac Arrest database, whose methods have been described previously.9 ROC Epistry-Cardiac Arrest is a prospective population based registry of consecutive EMS attended out-of-hospital cardiac arrests.9 The Toronto Regional RescuNet site contains OHCA from rural and urban regions in southern Ontario, a population of over
Results
From January 1, 2007 to April 30, 2013, there were a total of 20,165 adult OHCA treated by EMS personnel. Of these patients, 871 were eligible for post-cardiac arrest TTM and met the study inclusion criteria (Fig. 1). There were 622 (71.4%) patients who survived to hospital discharge and of these patients, 487 (78.1%) had a good functional survival (mRS 0–3).
Clinical characteristics of patients with good functional survival and poor functional survival at hospital discharge are reported in
Discussion
In our study, the use of TTM was associated with overall improved functional outcome, and this effect was dependent upon the time of initial defibrillation. These findings align with the initial 3-phase model of cardiac arrest proposed by Weisfeldt and Becker.3 In this model, the authors proposed that cardiac arrest treatment should be tailored to each specific time-sensitive phase of cardiac arrest physiology. Furthermore, they suggested that once a patient had been in cardiac arrest for
Limitations
Although the data presented was derived from a large population based data set, there were several limitations that must be considered when interpreting the results. As with other retrospective observational studies, there was a risk of measurement bias in data collection, however, this risk was minimized with the use of trained data guardians, standardized data definitions and abstraction instructions, computerized logic and error checks at point of data entry, and random re-abstraction for
Conclusion
In this study, longer delays from the time of collapse to initial defibrillation resulted in both decreased survival and good functional outcome at hospital discharge in patients resuscitated from OHCA. However, the use of TTM was associated with improved functional survival and its therapeutic effect was more pronounced in patients with prolonged times to initial defibrillation.
Conflict of interest statement
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.04.017.