Inducing hypothermia after out of hospital cardiac arrestBMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2735 (Published 11 April 2014) Cite this as: BMJ 2014;348:g2735
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In his recent editorial, Bernard has highlighted the importance of the Targeted Temperature Management (TTM) trial in the evolution of our understanding of targeted temperature control after cardiac arrest . This study compared a target temperature of 36oC with that of 33oC for 24 hours after out of hospital cardiac arrest and found no difference in survival or neurological outcomes between the two groups . We are concerned that the title of the editorial creates the impression that targeted temperature control should be abandoned. We wish to draw attention to the current guidance from the International Liaison Committee on Resuscitation (ILCOR) (http://www.ilcor.org/data/TTM-ILCOR-update-Dec-2013.pdf), which, regardless of the target temperature, highlights the importance of ensuring control of temperature in the critical hours and days after return of spontaneous circulation. Such temperature control implies the need for an active process to maintain the target temperature. Without active efforts to keep the temperature down, many of these patients will develop a significant fever caused by the inflammatory response associated with the post cardiac arrest syndrome . In an observational study of 151 post cardiac arrest patients, the risk of an unfavourable neurological outcome increased for each degree Celsius higher than 37oC (odds ratio 2.26; 95% confidence interval (CI) 1.24 – 4.12) .
Although Dr Bernard suggests that the results of the TTM trial should ‘change practice immediately’ and that we should aim for a target temperature of 36oC in post cardiac arrest patients, others are less certain that we should abandon the target of 33oC . The median ‘no flow’ time in both arms of the TTM was just 1 min (interquartile range 0 – 2 min). A large observational study of patients with witnessed out-of-hospital cardiac arrest documented a significant benefit of therapeutic hypothermia only with ‘no-flow’ times of more than 2 min .
We agree with Bernard and the TTM investigators that one of the most important developments in post resuscitation care has been the evolution of more sophisticated prognostication. Allowing the brain more time to recover before prognostication and withdrawal of treatment has the potential to save many lives .
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Competing interests: JPN is Co-editor of the International Liaison Committee for Resuscitation 2015 Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations and Vice Chair of the European Resuscitation Council JS is European Resuscitation Council Advanced Life Support (ALS) Working Group Chair, and International Liaison Committee for Resuscitation ALS Task Force co-chair and lead for the Resuscitation Council (UK) Guidelines process. GDP is Chair of the Resuscitation Council (UK) Advanced Life Support Subcommittee.