Major International Trial Clarifies Oxygen Therapy After Cardiac Arrest

A major international study led by researchers from the Medical Research Institute of New Zealand (MRINZ) has found that a conservative oxygen therapy strategy does not improve survival or neurological recovery in adults receiving intensive care after cardiac arrest. 

The findings, published in The New England Journal of Medicine, come from the LOGICAL trial, a randomised controlled trial involving 1,840 patients across 53 intensive care units in Australia, New Zealand and Ireland. 

For more than a decade, researchers have investigated whether limiting exposure to higher oxygen levels after cardiac arrest could reduce brain injury and improve recovery. Earlier observational studies and animal research suggested excessive oxygen exposure might worsen reperfusion-related brain injury, but clinical evidence has remained uncertain. 

The LOGICAL trial compared a conservative oxygen strategy designed to minimise exposure to higher oxygen levels with a more liberal oxygen approach in unconscious adults requiring mechanical ventilation after cardiac arrest. 

Professor Paul Young, Co-Lead Investigator of the LOGICAL trial and intensive care specialist at MRINZ and Wellington Hospital, says the study provides the clearest evidence to date on this important clinical question. 

“There were good biological reasons to think that reducing oxygen exposure after cardiac arrest might improve outcomes, and some previous studies had suggested possible benefits,” says Professor Young. 

“What LOGICAL shows is that a conservative oxygen strategy did not increase the likelihood of survival with a favourable neurological outcome compared with a liberal oxygen strategy.” 

At six months after enrolment, 38.2% of patients receiving conservative oxygen therapy had survived with a favourable functional outcome compared with 39.7% of patients receiving liberal oxygen therapy. Survival, quality of life, cognitive outcomes, duration of ventilation, and hospital length of stay were also similar between treatment groups. 

The trial achieved clear separation between the oxygen strategies, confirming that patients in the two groups experienced meaningfully different levels of oxygen exposure. 

Professor Carol Hodgson, Co-Lead Investigator from Monash University and the Australian and New Zealand Intensive Care Research Centre, says the findings help resolve a long-standing uncertainty in post-cardiac arrest care. 

“Oxygen is one of the most commonly used therapies in intensive care, but determining the optimal oxygen target after cardiac arrest has been challenging,” says Professor Hodgson. 

“These results suggest that routinely targeting lower oxygen levels after cardiac arrest is unlikely to provide meaningful clinical benefit.” 

“Current evidence suggests that avoidance of mild hyperoxaemia is unnecessary, while avoidance of both hypoxaemia and extreme hyperoxaemia remains reasonable,” says Professor Young. 

The researchers say the findings will help guide oxygen therapy practices in intensive care units internationally while informing future guideline development. 

The LOGICAL trial was funded by the Health Research Council of New Zealand, the Alpha Charitable Trust, the David and Cassie Anderson Medical Charitable Trust, the National Health and Medical Research Council of Australia, and the Irish Critical Care Clinical Trials Network. 

Read the full New England Journal of Medicine publication here.