Mild hypercapnia increases cerebral blood flow and may improve neurologic outcomes. This study aimed to determine the effects of mild hypercapnia compared to normocapnia on neurologic outcomes in adults with coma following out-of-hospital cardiac arrest. A total of 1700 patients from 63 intensive care units (ICUs) in 17 countries were randomly assigned to receive either mild hypercapnia or normocapnia. The primary outcome measured was a favorable neurologic outcome at 6 months, while secondary outcomes included death within 6 months.
The results showed that there was no significant difference in favorable neurologic outcomes between the mild hypercapnia group (43.5%) and the normocapnia group (44.6%) at 6 months. Similarly, the incidence of death within 6 months did not differ significantly between the two groups, with 48.2% in the mild hypercapnia group and 45.9% in the normocapnia group. The occurrence of adverse events was comparable between the two groups.