Conservative Oxygen Therapy Fails to Improve Functional Survival After Cardiac Arrest: Study
Australia: A conservative oxygen therapy strategy did not improve the chances of survival with a favorable functional outcome among unresponsive adults receiving intensive care after cardiac arrest, a study published in The New England Journal of Medicine has suggested. The findings suggest that restricting oxygen exposure after resuscitation offers no clear advantage over a more liberal oxygen approach in this patient population.
The study was led by Carol L. Hodgson from the Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia, and colleagues.
Oxygen therapy is a key component of post–cardiac arrest care. However, excessive oxygen exposure may contribute to oxidative injury, prompting researchers to investigate whether a more conservative oxygen strategy could improve neurological recovery and survival outcomes in critically ill patients who remain unresponsive after resuscitation.
To examine this question, the investigators conducted a randomized clinical trial involving adults who required mechanical ventilation in intensive care units (ICUs) following cardiac arrest. Participants were assigned to either conservative oxygen therapy or liberal oxygen therapy. In both groups, the lower oxygen saturation target measured by pulse oximetry was set at 90%.
Patients in the conservative-oxygen group had an upper oxygen saturation alarm limit of 95%, and the fraction of inspired oxygen was reduced to room-air levels whenever possible while maintaining adequate oxygenation. In contrast, patients receiving liberal oxygen therapy had no upper oxygen saturation restriction, and the lowest permitted inspired oxygen concentration during mechanical ventilation was 30%.
The trial enrolled 1,840 patients across 53 ICUs in Australia, New Zealand, and Ireland. Of these, 882 patients received conservative oxygen therapy, while 958 received liberal oxygen therapy.
The primary outcome was survival with a favorable functional status 180 days after cardiac arrest, assessed using the Extended Glasgow Outcome Scale (GOS-E). A favorable outcome was defined as survival with at least moderate functional independence.
Key findings from the study included:
- A favorable functional outcome at 180 days was achieved in 38.2% of patients receiving conservative oxygen therapy.
- In the liberal-oxygen group, 39.7% of patients experienced a favorable functional outcome.
- The difference between the two treatment strategies was not statistically significant.
- No treatment-related adverse events were reported.
The researchers noted several limitations, including protocol deviations in achieving oxygen targets, potential limited generalizability beyond Australia, New Zealand, and Ireland, and the fact that clinicians were aware of treatment assignments, although outcome assessors remained blinded.
Overall, the findings indicate that a conservative oxygen strategy did not improve survival with favorable neurological and functional recovery compared with liberal oxygen therapy in mechanically ventilated ICU patients following cardiac arrest. The authors concluded that limiting oxygen exposure beyond standard care does not appear to provide additional benefit in this setting.
Reference:
DOI: 10.1056/NEJMoa2513814
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