SNOWMASS, COLO. – Targeted temperature management maintained at 32-36 degrees Celsius is now a strong class I recommendation for all comatose patients who experience return of spontaneous circulation after out-of-hospital cardiac arrest, including those with nonshockable rhythms, Erin A. Bohula, MD, PhD, said at the annual Cardiovascular Conference at Snowmass sponsored by the American College of Cardiology.
“Our practice is that,” said Dr. Bohula, a cardiologist and critical care specialist at Brigham and Women’s Hospital and Harvard Medical School, Boston.
The current ACC/AHA guidelines declare: “There are essentially no patients for whom temperature control somewhere in the range between 32 degrees C [89.6 F) and 36 degrees C [96.8 F] is contraindicated.” The writing committee cited “recent clinical trial data enrolling patients with all rhythms, the rarity of adverse effects in trials, the high neurologic morbidity and mortality without any specific interventions, and the preponderance of data suggesting that temperature is an important variable for neurologic recovery” (Circulation. 2015 Nov 3;132[18 Suppl 2]:S465-82).
“That’s a pretty strong statement,” Dr. Bohula observed.
The current guidelines, which date back to 2015, give a class I, level of evidence B recommendation for targeted temperature management (TTM) in patients who are comatose with return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest involving ventricular fibrillation or pulseless ventricular fibrillation. The bedside definition of comatose is lack of meaningful response to verbal commands to squeeze hands, blink, or move toes.
The current recommendation for TTM in patients resuscitated from out-of-hospital cardiac arrest with a nonshockable rhythm is class I, level of evidence C, meaning it’s based on expert consensus. However, that recommendation is now out of date and due for a level-of-evidence upgrade in light of the recent results of the French HYPERION trial, an open-label randomized trial of 584 patients resuscitated from cardiac arrest with a nonshockable rhythm. Although 90-day mortality was similarly high in the TTM and targeted normothermia groups, the rate of favorable neurologic outcome as assessed by a Cerebral Performance Category scale score of 1 or 2 was 10.2% in the TTM group, significantly better than the 5.7% rate in controls (N Engl J Med. 2019 Dec 12;381:2327-37).
The 2010, ACC/AHA guidelines recommended a TTM range of 32-34 degrees C, but on the basis of subsequent persuasive randomized trial data, that range was broadened to 32-36 degrees C in the 2015 guidelines, with a class IB recommendation. Maintenance of TTM for at least 24 hours has a IIa, level of evidence C recommendation in the current guidelines.
The guidelines emphasize that specific features may favor selection of one temperature for TTM over another. For example, patients with seizures or cerebral edema might be better off with TTM at a lower temperature, while a higher temperature may be best for those with bleeding or severe bradycardia. At Brigham and Women’s Hospital, the default temperature is 33 degrees C. However, TTM with a goal of 36 degrees C is seriously considered in patients with recent head trauma, major surgery within the past 2 weeks, refractory hypotension, severe sepsis, pregnancy, or high bleeding risk. Rewarming is done at a rate of 0.25 degrees C per hour, with sedation maintained until the patient has been returned to 98.6 degrees F, according to Dr. Bohula.
Based on several negative studies of TTM using rapid infusion of chilled fluids in the ambulance en route to the hospital, the guidelines rate that practice class IIIA, meaning don’t do it. Avoidance of a systolic blood pressure below 90 mm Hg and a mean arterial pressure of less than 65 mm Hg gets a class IIb level of evidence C recommendation to lessen the risk of cerebral hypoxia.