Clinical paperEffect of therapeutic hypothermia on the outcomes after out-of-hospital cardiac arrest according to initial ECG rhythm and witnessed status: A nationwide observational interaction analysis☆
Introduction
Out-of-hospital cardiac arrest (OHCA) is a public health problem worldwide. The American Heart Association estimates that about 424,000 emergency medical service (EMS)-assessed OHCA episodes, or 134 per 100,000 persons, occur each year in the United States.1 The incidence of EMS-assessed OHCA is estimated to be 86 per 100,000 person-years in Europe, and 53 per 100,000 person-years in Asia.2 OHCA is also associated with high morbidity and mortality, pooled data showing that approximately 23.8% of the patients survive to hospital admission but only 7.6% of the patients survive to hospital discharge.3 The major cause of in-hospital mortality in patients who are resuscitated and survive to hospital admission is attributed to the post-cardiac arrest syndrome, composed of brain injury, myocardial dysfunction, systemic ischemia, and reperfusion response. Therapeutic hypothermia (TH) is a part of the recommended bundle of care that targets the post-cardiac arrest syndrome.4
Two randomized controlled trials5, 6 published in 2002 demonstrated the survival benefit of TH in comatose OHCA patients due to ventricular fibrillation (VF), which led the International Liaison Committee on Resuscitation in 2003 to recommend TH to comatose adult survivors of VF OHCA.7 However, a recent landmark study by Nielsen et al.8 calls into question the benefit of induced hypothermia compared to maintaining normothermia in post-OHCA patients, showing that many questions on TH are still unresolved.9 Nonetheless, TH is still widely used and the current guidelines recommend cooling comatose adult patients with return of spontaneous circulation (ROSC) to 32 °C to 34 °C for 12 to 24 h after VF OHCA (Class I, LOE B), and in-hospital cardiac arrest (IHCA) or after OHCA with an initial rhythm of pulseless electric activity (PEA) or asystole (Class IIb, LOE B).9, 10
Numerous observational studies have confirmed the improvement in neurological outcomes and survival in OHCA with shockable initial rhythms.11, 12 However, the initial rhythm in the majority of OHCA is PEA/asystole,2 and the guidelines support the use of TH in non-shockable rhythms while recognizing and emphasizing the need for further studies. There are no randomized controlled trials that directly test the benefit of TH in non-shockable rhythms, and results of observational studies have been conflicting. Recent meta-analysis of observational studies have shown an association with improved outcomes, but state that the quality of the evidence is poor.13, 14
Further studies are needed to refine the details of TH, including the target population. In unwitnessed, non-shockable OHCA patients, it is debatable whether TH is associated with better outcomes. This study aimed to provide further evidence by comparing the effect of TH for the improvement of neurological outcome and survival to discharge in cardiac arrest patients, and the interaction effects of initial ECG rhythm and presence of witness on the effect of TH on outcomes.
Section snippets
Study setting and design
This is a retrospective observational study using a Korean national EMS-assessed OHCA cohort database, the Cardiovascular Disease Surveillance (CAVAS) project. The project started in 2006 and is sponsored by the National Emergency Management Agency and the Centers for Disease Control and Prevention of the Republic of Korea.15, 16, 17, 18, 19, 20 Data from EMS run sheets and hospital record reviews were used to form the database. Cases of OHCA were identified from the electronic EMS run sheets
Demographic findings
There were 11,335 adult OHCA patients of presumed cardiac origin who survived to hospital admission during the study period. Seventy-nine patients without neurological outcome data, 9 of whom underwent TH, were excluded from the study (Fig. 1). There were 11,256 patients in the final analysis, of whom 15.1% or 1703 patients were treated with TH, and 84.9% or 9553 patients formed the control group. The number of cases and the percentages of OHCA patients receiving TH increased yearly from 5.5%
Discussion
In the multifaceted approach to the care of patients with post cardiac arrest syndrome,4 TH is a treatment that has been shown to improve outcomes.4, 21 In this study, TH improved both neurological outcome and survival to discharge in OHCA patients in Korea. There was also an interaction effect that improvements to outcome were most pronounced in witnessed OHCA patients with PEA as their initial ECG rhythm.
Because of the relatively higher rate of survival compared to OHCA presenting with
Conclusion
In a nationwide observational study of OHCA and therapeutic hypothermia in Korea, therapeutic hypothermia use has been increasing every year and is associated with better neurological outcome and higher survival to discharge. The effect is greatest in witnessed patients with PEA as the initial ECG rhythm. More studies are needed to further elucidate the target population who will most benefit from TH.
Conflict of interest statement
The authors declare no conflict of interest relevant to this paper.
Acknowledgements
This study was supported by the National Emergency Management Agency of Korea and the Korea Centers for Disease Control and Prevention (CDC). The study was funded by the Korea CDC (2012–2014) (Grant Nos.: 2012-E33010-00; 2013-E33015-00; 2014-E33011-00).
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Effect of target temperature management at 32–34 °C in cardiac arrest patients considering assessment by regional cerebral oxygen saturation: A multicenter retrospective cohort study
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2018, ResuscitationCitation Excerpt :This result indicated that even prolonged resuscitation cannot justify the futility of aggressive post-cardiac arrest management. TTM showed less significant improvement or no improvement in neurological outcomes in OHCA patients with a shockable rhythm or patients with diabetes [26,27]. Outcomes may be affected according to the cooling methods for patients with specific conditions; however, the studies were not adjusted for the cooling methods.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2015.12.012.