No Added Benefit of Cooler Temps in Therapeutic Hypothermia for Out-of-Hospital Cardiac Arrest

May 19, 2021

By Nancy Melville

VIRTUAL -- May 18, 2021 -- Patients who are comatose after experiencing out-of-hospital cardiac arrest and cooled with therapeutic hypothermia to a target of 31 degrees Celsius show no improvement in neurological outcomes compared with the use of hypothermia with the more standard target of 34 degrees Celsius, according to a study presented at the Virtual 70th Annual Scientific Sessions of the American College of Cardiology (ACC).

“The results of our trial do not support the use of moderate therapeutic hypothermia of 31degrees Celsius to improve neurological outcomes in comatose survivors of out-of-hospital cardiac arrest,” said Michel R. Le May, MD, University of Ottawa Heart Institute, Ottawa, Ontario.

The CAPITAL CHILL trial included 367 patients who were treated for out-of-hospital cardiac arrest and successfully resuscitated but remained comatose at the Ottawa Heart Institute between 2013 and 2020. Patients were randomised 1:1 to a target temperature of 31 or 34 degrees Celsius using an endovascular device. Patients were stratified according to initial heart rhythm at the time of the cardiac arrest, either as shockable (ventricular fibrillation or ventricular tachycardia) or non-shockable (asystole or pulseless electrical activity).

Although the study was double-blind, nurses were aware of the temperatures, but physicians were blinded.

For the primary outcome -- a composite of all-cause mortality or poor neurological outcome at 180 days -- there were no significant differences between the 31 degrees group (48.4%) or the 34 degrees group (45.4%; P = .56).

Individually, for mortality, the rates were 43.5% versus 41.0%, respectively (P = .63), and the rates for poor neurologic outcome were 4.9% versus 4.4%, respectively (P = .81).

There were also no significant differences between the groups in terms of secondary outcomes of pneumonia, renal replacement therapy, seizure, and stroke. Bleeding and thrombosis rates were also not statistically different.

The 31degrees group did have a significantly longer median length of stay in the cardiac intensive care unit (10 days versus 7; P = .004), but not in the cardiac center.

“This was the first randomised controlled trial to evaluate the benefits of therapeutic hypothermia with a target temperature below 32 degrees Celsisus ,” said Dr. Le May, noting that more research is needed to better understand inconsistent findings from other studies.

“It may be useful to pool all these studies together and try to figure out if there is a particular temperature that’s more suitable in particular cases,” he said. “We also have to find better, noninvasive tools to assess the brain and perhaps turn our attention toward a more personalised way of treating these patients. This would allow us to select the protocol that optimises the benefit for a particular patient.”[Presentation title: Therapeutic Hypothermia Following Out-of-Hospital Cardiac Arrest: a Randomized Trial Comparing Mild and Moderate Therapeutic Hypothermia]