Clinical paperThe impact of peri-shock pause on survival from out-of-hospital shockable cardiac arrest during the Resuscitation Outcomes Consortium PRIMED trial☆
Introduction
Survival from out-of-hospital cardiac arrest (OHCA) continues to challenge Emergency Medical Services (EMS) systems.1, 2, 3 With an annual incidence of greater than 190,000 treated cardiac arrests per year in North America alone, the search continues for the components of resuscitation essential to improved survival. Historically, predictors of survival from OHCA such as the Utstein data elements, have focused on system (response time, time to first shock, bystander CPR, bystander witnessed state, public location) and patient (age, presence or absence of shockable rhythm) characteristics.4 Previous research has demonstrated that Utstein variables alone are insufficient to accurately predict outcome from OHCA.5 With the advent of the 2010 American Heart Association-International Liaison Committee on Resuscitation (AHA-ILCOR) guidelines for Cardiopulmonary Resuscitation (CPR), renewed interest has focused on improving survival through improvements in the characteristic components of cardiopulmonary resuscitation (CPR).6, 7
CPR metrics such as peri-shock pause, chest compression fraction (CCF), chest compression depth, chest compression rate, and chest recoil may all impact cardiac arrest outcomes.8, 9, 10, 11, 12, 13 A previous study by the Resuscitation Outcomes Consortium (ROC) employing the Consortium's cardiac arrest registry database demonstrated a significant association between both pre- and peri-shock pause (PSP) duration and survival from shockable OHCA.14 Limitations to this study include sample size, lack of participation by all ROC sites, lack of neurologically intact (Modified Rankin Score ≤3 or Cerebral Performance Category) outcome data, high rate of missing shock pause data as well as a regression model that did not control for other CPR metrics (CCF, compression depth and compression rate). In June 2007, ROC sites began enrolling patients in the Prehospital Resuscitation Impedance Valve and Early vs. Delayed Analysis Randomized Controlled trial known as ROC PRIMED.15 Given the trial's size and its broad participation by all ROC sites, it provided a more robust data set to validate our previous findings. We therefore sought to estimate the strength of association between peri-shock pause duration and survival from shockable OHCA during the ROC PRIMED randomized controlled trial.
Section snippets
Setting and design
The ROC consists of 10 Regional Clinical Centers across North America, 7 in the United States (Pittsburgh, Pennsylvania; Dallas, Texas; Milwaukee, Wisconsin; Birmingham, Alabama; Seattle/King County, Washington; Portland, Oregon; and San Diego, California) and 3 in Canada (Toronto, Ontario; Vancouver, British Columbia and Ottawa, Ontario) as well as their respective EMS systems.16, 17 From June 2007 to November 2009, one hundred and fifty EMS agencies participated in the ROC PRIMED randomized
Results
Fig. 1 displays a consort diagram of all patients treated during the ROC PRIMED trial as well as the cohort included (n = 2006) in our statistical analysis. Table 1 displays baseline characteristics for VF/VT cases included and VF/VT cases excluded (due to lack of available or interpretable ECG recordings) from the study. The study population was similar with respect to sex, witnessed status, bystander CPR, and location compared to those without CPR process measures. Median (IQR) age was lower in
Discussion
To the best of our knowledge, this study represents the largest out-of-hospital study to date examining the relationship between peri-shock pause and survival to hospital discharge from shockable cardiac arrest. We have confirmed previous work on peri-shock pauses, further strengthening the conclusion that peri-shock pauses <20 s in the early resuscitation period are strongly associated (OR: 1.82, 95% CI: 1.17, 2.85) with survival to discharge when compared to episodes with peri-shock pause ≥40
Conclusion
In patients with cardiac arrest presenting in a shockable rhythm during the ROC PRIMED trial, pre-shock pauses <10 s and peri-shock pauses <20 s were significantly associated with higher odds of survival to both hospital discharge and neurologically intact (MRS ≤ 3) survival. Future cardiopulmonary education and technology should focus on minimizing all pre-shock pauses.
Conflict of interest statement
Drs. Cheskes, Christenson, Menegazzi, Idris as well as Susanne May and Judy Powell receive ROC grant funding. Dr. Brooks was supported by a Heart and Stroke Foundation Jumpstart Resuscitation Scholarship. Dr. Cheskes has received speaking honorarium from Zoll Medical. No other grant disclosures.
Funding sources
The ROC is supported by a series of cooperative agreements to nine regional clinical centers and one Data Coordinating Center (5U01 HL077863 – University of Washington Data Coordinating Center, HL077866 – Medical College of Wisconsin, HL077867 – University of Washington, HL077871 – University of Pittsburgh, HL077872 – St. Michael's Hospital, HL077873 – Oregon Health and Science University, HL077881 – University of Alabama at Birmingham, HL077885 – Ottawa Hospital Research Institute, HL077887 –
Acknowledgements
We would like to acknowledge the hard work and dedication of all the EMS and fire agencies participating in the Resuscitation Outcomes Consortium. Research in the pre hospital setting would not be possible without the tireless efforts of their paramedics and firefighters. A special thanks to all the data abstractors and coordinators at each of the participating sites for their diligence and patience in abstracting the data from a mountain of CPR process files required for this study.
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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.2013.10.014.