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Therapeutic hypothermia is likely to improve neurologic outcomes in patients who are comatose following out-of-hospital cardiac arrest (OHCA), and should be offered, according to a new guideline from the American Academy of Neurology (AAN).

Cooling the body to 32 to 34 degrees Celsius (89.6 to 93.2 degrees Fahrenheit) for 24 hours following OHCA with an initial cardiac rhythm of pulseless ventricular tachycardia or ventricular fibrillation scored a Level A recommendation for improving neurologic outcomes compared with no cooling, Romergryko Geocadin, MD, co-director of the Encephalitis Center at Johns Hopkins Medicine in Baltimore, and other members of the AAN's Guideline Development, Dissemination, and Implementation Subcommittee, wrote in the document, online in .

There is also Level B evidence that targeted temperature management -- cooling to 36º C (96.8º F) for 24 hours, followed by rewarming to 37.5º C (99.5º F) over 8 hours -- is as effective as standard therapeutic hypothermia for OHCA patients whose initial rhythm was VT/VF or asystole/pulseless electrical activity and is an acceptable alternative, the team noted.

"People who are in a coma after being resuscitated from cardiac arrest require complex neurologic and medical care, and neurologists can play a key role in improving outcomes by providing body cooling," Geocadin said in a statement. "This guideline recommends that cooling is used more often for patients who qualify."

The team reviewed studies of therapeutic hypothermia conducted from 1966 to 2016. A Level C recommendation was given to therapeutic hypothermia for improving neurologic outcomes for comatose OHCA patients whose initial rhythm was pulseless electrical activity or asystole.

"Induced mild hypothermia has emerged as an effective therapy to improve outcomes in patients with VT/VF as their initial cardiac rhythm, but its role in patients with pulseless electrical activity or asystole remains uncertain."

The document also highly recommends against offering prehospital cooling (Level A).

Geocadin and colleagues cautioned that other aspects of therapeutic hypothermia require further study, including determining the optimal method for inducing and maintaining therapeutic hypothermia, the ideal rate of cooling, and the optimal target temperature range.

There is also a need to investigate the protocols for rewarming, which have often varied between studies and could explain some variation in results, the team said. "No method has established superiority, and clinicians need to understand existing methods and technologies so they are better informed when acquiring equipment and developing protocols."

In a statement, Geocadin charged patients' families with asking their physician "if their loved one qualifies for body cooling."