Clinical paperClinical outcomes following out-of-hospital cardiac arrest: The minute-by-minute impact of bystander cardiopulmonary resuscitation
Introduction
The disease burden from non-traumatic out-of-hospital cardiac arrest (OHCA) is important, with close to North American 400,000 cases each year and only 10% of treated patients surviving their episode.1, 2, 3, 4, 5, 6, 7, 8, 9 Despite a generally poor prognosis, OHCA prognostication remains complex but important since it can influence many important treatment decisions and allows systems optimization for OHCA care.10 Amongst factors of good prognosis, the provision of cardiopulmonary resuscitation (CPR) has notably been associated with improved survival and neurologic outcomes for OHCA patients.11, 12, 13, 14, 15 This effect is postulated to be resulting from blood flow restoration, with a consequent decrease in ischemia, but this restoration of blood flow has only been directly described in patients receiving CPR from professionals, usually in the context of an in-hospital cardiac arrest or in animal models.15
Longer delays before the CPR provision have previously been associated with worse outcomes.10, 16, 17 The period (heart arrest to CPR initiation) is referred to as no-flow time (NFT), while the length of time during which CPR is provided is known as low-flow time (LFT).18, 19, 20 The general association between bystander CPR and good clinical outcomes is well recognized, but the time-dependent prognostic role of bystander CPR has not been described with great precision, especially for neurologic outcomes.16, 17, 21 Longer delays before emergency medical services (EMS) arrival (EMS response time) have also been associated with worse outcomes.17, 22 As such, the benefits of the provision of a definite amount of bystander CPR, transforming the length of time which would have been NFT into bystander LFT (BLFT), to mitigate EMS response time is uncertain.
A better understanding of these dynamics could guide future interventions aiming to improve the rate of bystander CPR or EMS response times and our ability to prognosticate OHCA patients. Therefore, this study’s objective is to evaluate the association between bystander CPR, EMS response time, and clinical outcomes of OHCA patients.
Section snippets
Study design and setting
This cohort study was derived from the Resuscitation Outcomes Consortium (ROC) OHCA registry (ROC Epistry) Version 1 and 2 (December 1st, 2005 to April 1st, 2010) and 3 (April 1st, 2011 to June 30th, 2015), which included cases assessed by EMS in the out-of-hospital setting who: a) underwent either EMS-performed chest compressions or had a shock delivered by a bystander-applied automated external defibrillator; or b) were found pulseless by EMS personnel, but did not receive treatment.23
Cohort description
A total of 229,632 patients were logged in the registries, from whom 41,012 (17.9%) met inclusion and exclusion criteria (Fig. 1). A total of 18,867 patients (46.0%) did not receive bystander CPR and had a median EMS response time (or NFT) of 7.9 min (IQR 6.1–10.0). A total of 22,145 patients (54.0%) received bystander CPR and had a median EMS response time (or BLFT) of 7.8 min (IQR 6.0–9.9). Their demographic and clinical characteristics are presented in Table 1. Notably, patients with shorter
Discussion
In this large multicenter analysis of bystander-witnessed OHCA, we observed that bystander CPR was strongly associated with good clinical outcomes. However, bystander CPR did not mitigate the negative association between longer EMS response time and clinical outcomes (-8% per minute for survival and −12% per minute for survival with a good neurologic outcome). Outcomes were still significantly better for those with bystander CPR when comparing patients with similar EMS response time in all time
Conclusions
Bystander CPR is associated with an immediate increase in the odds of survival to hospital discharge and of survival with a good neurologic outcome for OHCA patients, which could partly be attributed to bystander-provided defibrillation. However, bystander CPR did not influence the negative association between longer EMS response time and clinical outcomes, albeit patients receiving bystander CPR had significantly higher rates of good outcomes in all time categories. Future studies should
Author Affiliations
Faculty of Medicine, Department of Family Medicine and Emergency Medicine (Cournoyer, Lessard, Chauny, Morris, Castonguay, Daoust); Department of Medicine (Cavayas, Albert, Potter); Department of Surgery (Lamarche); and Faculty of Nursing (Cossette), Université de Montréal, Montréal, Canada. Department of Emergency Medicine (Cournoyer, Segal, Lessard, Chauny, Morris, Castonguay, Daoust); Department of Medicine (Cavayas, Albert); Department of Surgery (Lamarche); and Research Center (Cournoyer,
Author Contributions
Dr Cournoyer had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Cournoyer, Chauny, Paquet, Marquis, Cossette, Castonguay, Morris, Lessard, Daoust.
Acquisition, analysis, or interpretation of data: All authors.
Drafting the manuscript: Cournoyer.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Cournoyer, Paquet.
Obtained funding:
Funding/Support
This project received funding from the ‘Fonds des Urgentistes de l’Hôpital du Sacré-Cœur de Montréal’ and the ‘Département de médecine familiale et de médecine d’urgence de l’Université de Montréal’.
Role of the Funder/Sponsor
The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Financial support
This project received funding from the ‘Département de médecine familiale et de médecine d’urgence de l’Université de Montréal’ and the ‘Fonds des Urgentistes de l’Hôpital du Sacré-Cœur de Montréal’. The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Conflict of interest
Dr Cheskes has receiving funding from Zoll Medical and Stryker Corporation for educational speaking on CPR Quality. Dr Cheskes has received investigator-initiated research funding from Zoll Medical for research studies. The other authors have no other conflicts of interest to declare.
Acknowledgements
The Resuscitation Outcomes Consortium (ROC) is supported by a series of cooperative agreements with 10 regional clinical centres and one data Coordinating Centre (5U01HL077863,HL077881, HL077871, HL077872, HL077866, HL077908, HL077867, HL077885, HL077887, HL077873,HL077865) from the National Heart, Lung, and Blood Institute in partnership with the National Institute of Neurological Disorders and Stroke, U.S. Army, Medical Research & Material Command, the Canadian Institutes of Health Research _
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