Hypoxemia linked to severe disability at 18 months.

FROM JAMA

Intermittent episodes of hypoxemia lasting more than 1 minute during the first 2-3 months after extremely preterm birth are associated with severe disability at age 18 months, according to researchers.

Almost all extremely preterm infants experience intermittent hypoxemia during their neonatal intensive care unit stay, but the relationship between this hypoxemia and later neurodevelopmental problems is uncertain. Researchers did a post hoc analysis of data gathered in the multicenter Canadian Oxygen Trial, which compared the effects of lower (85%-89%) vs. higher (91%-95%) oxygen saturation targets in preterm infants. The study focused on 1,019 infants born at 23-27 weeks' gestation who survived to 36 weeks' postmenstrual age, said Dr. Christian F. Poets of the department of neonatology at Tuebingen (Germany) University Hospital.

Dr. Poets and associates assessed whether hypoxemia correlated with the composite outcome of death after 36 weeks' postmenstrual age or disability--motor impairment, cognitive or language delay, severe hearing loss requiring hearing aids or cochlear implants, bilateral blindness, or severe retinopathy of prematurity--assessed at a corrected age of 18 months. These adverse outcomes occurred in 43% of the study population.

The mean percentage of time with hypoxemia ranged from 0.4% in the lowest decile to 13.5% in the highest. The probability of each adverse outcome increased significantly as the percentage of time in hypoxemia increased. For the primary outcome of late death or disability, relative risk was 1.53 for infants in the highest vs. the lowest decile. Hypoxemic episodes were associated with death or severe disability in 56.5% of infants in the highest decile of hypoxemia exposure, compared with 36.9% in the lowest decile. Each adverse outcome also followed this pattern of risk (JAMA. 2015;314[6]:595-603). Only prolonged episodes of hypoxemia lasting more than 1 minute correlated with adverse outcomes; shorter episodes did not. The risk of adverse outcomes increased as age at the time of hypoxemia episodes increased, so the greatest risk was observed in infants whose hypoxemia occurred 9-10 weeks after birth.

The post hoc study design generates hypotheses for future research, not definitive conclusions, so it is not known whether prolonged intermittent hypoxemia contributes to neurodevelopmental impairment or is just a feature that denotes which infants are destined to develop impairments. If future studies show that hypoxemia is a cause of adverse outcomes, it may be a preventable cause--perhaps with caffeine therapy, specific ventilator strategies, or doxapram administration, the researchers said.

This study was funded exclusively by the Canadian Institutes of Health Research. Dr. Poets reported receiving research grants from Chiesi Farmaceurici SpA and Masimo.

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