BOX Trial (Duration)

Fever is common among critically ill patients, caused by an increase in the set point for core body temperature and can have harmful effects.

Fever prevention for 72 hours after cardiac arrest has been endorsed by international guidelines since 2005, but data from randomized trials supporting this intervention after the initial 24 hours of temperature control are lacking.

Two large, randomized trials investigated hypothermic temperature control for 24 hours at 33°C vs. normothermia in patients with out-of-hospital cardiac arrest and found neutral results.

This randomized trial compared device-based fever prevention for 36 hours or 72 hours in comatose patients resuscitated after an out-of-hospital cardiac arrest.

No significant difference was found between the two durations in terms of the percentage of patients who died or had severe disability or coma, consistent across all prespecified subgroups.

The trial only investigated whether a device should be used for 36 or 72 hours and did not compare other non–device-based fever prevention methods.

Limitations of the trial include the unmasked temperature intervention, modest effectiveness in preventing low-grade fever, challenges in follow-up due to the COVID-19 pandemic, and the relatively good prognosis of the patient cohort.

The study concluded that active device-based fever prevention for 72 hours or 36 hours after cardiac arrest did not result in significantly different percentages of patients dying or having severe disability or coma.