New Findings on Conservative Oxygen After Cardiac Arrest

Key Takeaways

• At 180 days, survival with a favorable functional outcome occurred at a similar rate in the conservative-oxygen and liberal-oxygen groups.
• Both groups used a default lower SpO2 limit of 90%, while the conservative arm added a 95% upper alarm and FiO2 reduction to 0.21, and the liberal arm used no upper limit with a minimum FiO2 of 0.3.

In a randomized New England Journal of Medicine trial, conservative and liberal oxygen therapy produced similar 180-day survival with favorable functional outcomes in unresponsive adults receiving mechanical ventilation in the ICU after cardiac arrest. Favorable outcomes were reported in roughly 38% of the conservative-oxygen group and 40% of the liberal-oxygen group, with a relative risk of 0.97.

The randomized trial enrolled 1840 patients from 53 ICUs in Australia, New Zealand, and Ireland. Of these, 882 were assigned to conservative oxygen therapy and 958 to liberal oxygen therapy. Both groups had a default lower arterial oxygen saturation limit of 90%, but the conservative strategy set an upper SpO2 alarm at 95% and reduced FiO2 to 0.21 when saturation remained above the lower limit. The liberal strategy used no measures to limit upper SpO2 and allowed a minimum FiO2 of 0.3.

The prespecified primary outcome was survival with favorable functional outcome at 180 days, assessed with the Extended Glasgow Outcome Scale. Favorable functional outcome was defined as a GOS-E level of 5 or higher. Investigators reported this outcome in 313 of 819 patients (38.2%) in the conservative group and 353 of 890 patients (39.7%) in the liberal group, for a relative risk of 0.97. The 95% confidence interval was 0.87 to 1.09, and the P value was 0.65.

No adverse events were reported.