From surface to core: does better cooling make a difference after cardiac arrest?

Hypoxic-ischaemic brain injury (HIBI) is the primary cause of death in patients who are admitted to the intensive care unit (ICU) after out-of-hospital cardiac arrest (OHCA) [1]. Controlled hypothermia has been widely used to mitigate HIBI, following initial trials showing potential benefit from temperature control at 32–36 °C for 12–24 h after arrest [2]. However, in 2021, the TTM-2 randomised clinical trial (RCT)—that assigned 1900 adults with post-OHCA HIBI to controlled hypothermia at 33 °C or controlled normothermia with early treatment of fever (body temperature ≥ 37.8 °C) for 24 h followed by avoidance of fever in both arms for the first 72 h—showed no difference in mortality at 6 months [3]. Arrhythmia resulting in haemodynamic compromise was more common in the hypothermia arm. These results led the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) to recommend actively preventing fever for HIBI instead of hypothermia for the first 72 h in adult patients with HIBI [4].