Written by Andy Hogan
Cooling comatose patients to 33°C after out-of-hospital cardiac arrest did not improve mortality or neurological outcomes compared to simply maintaining normothermia (<37.8°C).
Why does this matter?
Initiating therapeutic hypothermia in the ED for post-arrest patients is resource-heavy and time-intensive. Hyperthermia prevention is a more attainable goal for busy emergency clinicians, especially if the end results are equivalent.
TTM2: leaving therapeutic hypothermia out in the cold
In the words of fashion icon Mugatu, challenging dogma for various emergency therapies is “so hot right now.” Much like tPA use in acute stroke, however, enthusiasm for therapeutic hypothermia after OHCA continues to cool (horrible pun intended). The TTM2 study by Dankiewicz et al. randomized a whopping 1861 patients and featured a rock-solid methodological design, free of the flaws that have limited prior analyses of targeted temperature management.
No significant difference in the primary outcome of 6-month mortality was found between hypothermia and normothermia groups (RR 1.05, CI 0.94 to 1.14), even after subgroup analysis. Similarly, unfavorable neurological outcomes (modified Rankin scores ≥4) at 6 months were not significantly different between groups (RR 1.00, CI 0.92 to 1.09). Furthermore, a significantly higher rate of hemodynamically unstable arrhythmias was observed in the hypothermia group (24 % vs. 17%, P<0.001).
Notably, the TTM2 study did not include a control group without any temperature management. The question of whether fever prevention impacts mortality or neurological outcomes remains unsettled for now. Although therapeutic hypothermia will still maintain some loyalists, the results of this study have practice-changing implications for most EDs & ICUs.
Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest. N Engl J Med. 2021;384(24):2283-2294. doi:10.1056/NEJMoa2100591.