Moderate hypothermia not superior to mild hypothermia following out-of-hospital heart attack

Among patients who had experienced an out-of-hospital cardiac arrest (OHCA), inducing moderate therapeutic hypothermia (cooling to 31°C) achieved no better outcomes than inducing mild hypothermia (cooling to 34°C) in terms of a poor neurological outcome or death in the CAPITAL CHILL trial [1].

While current guidelines for the management of patients who have experienced OHCA recommend targeted temperature management, it remains unclear what the optimal target temperature should be to achieve the most favourable outcomes. A pilot study of 36 patients suggested that better outcomes may be achieved by inducing hypothermia below the guideline-prescribed range of 32°C to 34°C [2]. The CAPITAL CHILL trial (NCT02011568) is the first randomised control trial to explore outcomes achieved by cooling OHCA patients to 31°C.

CAPITAL CHILL was a prospective, single-centre, randomised, double-blinded clinical trial which randomised 367 comatose survivors of OHCA to be cooled using an endovascular cooling device to a temperature of either 34° (n=183) or 32° (n=184) for a 24-hour period following OHCA. The primary outcome measure was the number of patients who experienced either a poor neurological outcome (as judged by a rehabilitation medicine specialist) or death at 6 months. The Disability Ratings Scale was used to rate the neurological outcome.

At 6 months, the primary outcome was realized by 48.4% of the participants in the moderate hypothermic group and 45.4% of the participants in the mild hypothermic group (relative risk [RR] 1.07; 95% CI 0.86-1.33; P=0.56). Among the mild hypothermic group, 41.0% of the patients died, compared with 43.5% of the patients in the moderate hypothermic group (RR 1.06; 95% CI 0.83-1.35; P=0.63).

Researchers conclude that their findings do not support changing current guidelines regarding post-OHCA therapeutic hypothermia.

1. 
   
   1. Le May M. Therapeutic Hypothermia Following Out-Of-Hospital Cardiac Arrest: A Randomized Trial Comparing Mild and Moderate Therapeutic Hypothermia (CAPITAL-CHILL Trial). Abstract 411-08, ACC 2021 Scientific Session, 15-17 May.
   2. Lopes-de-Sa E. Circulation 2012;126(24):2826-2833.

 



Posted on 19 May, 20216 July, 2021