A review of the utility of a hypothermia protocol in cardiac arrests due to non-shockable rhythms

Background: Therapeutic hypothermia and targeted temperature management are considered standard of care in the management of patients following out-of-hospital cardiac arrests due to shockable rhythms to improve neurological outcomes. In those presenting out-of-hospital cardiac arrests associated with non-shockable rhythms, the benefit of hypothermia is less clear. In this review we try to clarify the utility of implementing a hypothermia protocol after cardiac arrests due to non-shockable rhythms. Methods: PUBMED, Ovid, MEDLINE, EMBASE, and clinicaltrials. gov websites were searched through during October, 2016 using the terms "non shockable", "hypothermia," and "cardiac arrest." Studies were excluded if they solely evaluated in-hospital cardiac arrests, shockable rhythms, and/or pediatric patients. Data was extracted by two authors. Results: Forty studies were included in this review, most of which were not randomized or controlled, nor were they powered to make significant conclusions about the efficacy of hypothermia in this population. Some did evaluate specific factors that may portend to a better outcome in patients presenting with out-of-hospital cardiac arrest due to non-shockable rhythms undergoing hypothermia. Shortcomings included incorporating in-hospital cardiac arrest patients in analyses, comparing results of hypothermia in shockable versus non-shockable rhythm patients as an outcome measure, lacking standardization in cooling protocols, and short-term measures of outcomes. Conclusions: It was concluded that further study is needed to characterize patients presenting nonshockable rhythms who would benefit from hypothermia to better guide its use in this population given the costs and implications of treatment and long-term care in those who survive with poor outcomes.