TTM has long been a staple of post-cardiac arrest care, but its supporting evidence has changed. From 32°C to simply preventing fever, is temperature control actually making a difference or is it a misallocation of resources?
Last updated 12/5/24
Targeted Hypothermia (2002-2020)
Bernard and HACA (2002) demonstrated improved neurological outcomes with hypothermia at 32-34°C in comatose survivors of out-of-hospital cardiac arrest with shockable rhythms. The HYPERION Trial (2019) extended this concept to non-shockable rhythms, showing a potential benefit of hypothermia over normothermia in reducing poor neurological outcomes, though survival differences were not statistically significant.
- Primary Literature
- FOAMed Explanations
- Supportive evidence reviews: theNNT, Core EM, First 10EM
- HYPERION Trial analysis: RebelEM, PulmCrit
Supporting Literature for Normothermia (2021 - present)
The TTM2 trial, a randomized controlled trial (RCT), showed no difference in survival or neurological outcomes between hypothermia at 33°C and normothermia with fever prevention. A systematic review and meta-analysis published in Resuscitation evaluated multiple studies on temperature management strategies and concluded that fever prevention alone is non-inferior to hypothermia for improving survival and neurological outcomes. These findings reinforce the focus on fever control rather than routine hypothermia.
- Primary Literature
- TTM2 (2021) - 🔗 NEJM
- Systematic Review and Analysis (2021) - 🔗 Resuscitation
FOAMed Explanations
- TTM2 Review and criticism / limitations of prior literature: Pulmcrit, First 10 EM, Skeptics EM, Rebel EM, Journalfeed
- theNNT takes another look at all the available literature and updates their stance on therapeutic hypothermia following cardiac arrest
Current Guidelines
AHA Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
The 2023 AHA guidelines emphasize maintaining strict temperature control and preventing fever (>37.5°C) for comatose patients after ROSC, aligning with findings from recent literatue. They acknowledge that while hypothermia (32°C–34°C) is safe, there is no proven benefit over normothermia with fever prevention. Updates from 2020 include a shift in terminology from "targeted temperature management" to "temperature control".
Other Guidelines in favor of Normothermia
The European Resuscitation Council (ERC), the European Society of Intensive Care Medicine (ESICM) and the International Liaison Committee on Resuscitation (ILCOR) all recommend continuous core temperature monitoring and active fever prevention (>37.7°C) for at least 72 hours in comatose patients after ROSC, using antipyretics, exposure, or cooling devices targeting 37.5°C. Neither panel endorses temperature control at 32°C–36°C or early cooling due to insufficient evidence, and both advise against active rewarming of mildly hypothermic patients to normothermia. Prehospital cooling with large volumes of cold IV fluids is also not recommended.
- ERC-ESICM: 🔗 Read the Guideline
- ILCOR-CoSTR: 🔗 Read a draft of the Guideline