Lower oxygen-saturation targets associated with greater morbidity and mortality in extremely preterm infants: The BOOST-II study

1. A significantly higher risk of death and disability was found in extremely premature infants receiving lower-target oxygen-saturation compared to high-target oxygen-saturation.  

Evidence Rating Level: 1 (Excellent)

Study Rundown: Determining the oxygen saturation target range for preterm infants requires weighing the risks of hyperoxia and hypoxia, specifically with regards to retinopathy of prematurity. In this study, two multicenter RCTs were conducted between Australia and the UK to evaluate the effects of low- vs. high-target oxygen-saturation ranges on preterm infant’s morbidity and mortality. The primary outcome in both trials was death or disability at a corrected gestational age of 2 years. A higher rate of death or disability, albeit nonsignificant, was observed at 2 years within the individual trials. However, post-hoc unadjusted analyses of combined trial data showed a significantly increased risk of death in the lower-target group. Additionally, there was no significant difference between the lower-target and higher-target groups in terms of disability at 2 years in the individual trials and combined analyses. In general, this data is supportive of maintaining an oxygen saturation between 91%-95% to reduce mortality in extremely premature infants.

Click to read the study, published in NEJM

Relevant Reading: Safe oxygen saturation targeting and monitoring in preterm infants: can we avoid hypoxia and hyperoxia?

In-Depth [randomized controlled trial]: In this study, two randomized controlled trials were conducted between Australia and the UK. The Australian and UK trial randomized 1135 and 973 extremely preterm infants (born at least 24 hours before 28 weeks of gestational age) to either a low-target (85%-89%) or high-target (90%-95%) oxygen-saturation group. Primary analysis evaluated death or disability at a corrected gestational age of 2 years. In the Australian trial, the rate of death or disability was 45% (247/549 infants) in the lower-target group and 39.8% (217/545 infants) in the higher-target group (adjusted RR = 1.12; 95%[CI]=0.98-1.27; p=0.10). In the UK trial, the primary outcome occurred in 50.5% (185/366 infants) of the lower-target group and in 45.9% (164/357 infants) of the higher-target group (adjusted RR=1.10; 95%CI=0.97-1.24; p=0.15). However, in unadjusted analyses of the data that was combined from both trials, the lower-target group were found to have had an increased risk of death or disability than the higher-target group (48.1% vs. 43.1%; RR=1.11; 95% [CI]=1.01-1.23; p=0.02). Secondary outcomes included blindness, cerebral palsy, deafness, developmental delay and language deficits up to a corrected age of 2 years. In terms of secondary outcomes, there were no significant differences between groups in both the Australia and UK trial. 

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