NEW YORK (Reuters Health) – In neonates treated with therapeutic cooling for hypoxic ischemic encephalopathy, a higher fraction of inspired oxygen (FIO2) was significantly associated with adverse outcomes in a study from the UK.
Dr. Hemmen Sabir, who led the study, told Reuters Health by email, “It has long been known that breathing a high proportion of oxygen is damaging to the newborn brain. Cooling is protective for term babies in poor condition at birth. We now found that breathing a high proportion of oxygen remains damaging to the newborn brain, despite being cooled.”
“Our study underlines that you should keep the oxygen concentration as low as possible in cooled newborns,” he added.
His report was published online April 18th in the Journal of Pediatrics.
Dr. Sabir of the University of Bristol and colleagues monitored blood gases and ventilatory settings for six hours after birth in 61 such infants. Hypothermia was started at a median of 3 hours 45 minutes.
Twenty-three of the babies had poor outcomes. Eleven died; the other 12 had Mental Development Index or Psychomotor Development Index scores below 70 on Bayley II scales.
There was no association between any measures of hypocapnia and adverse outcome, but higher FIO2 was linked with adverse outcomes. For example, 14 newborns had an AUC-FIO2 of greater than 0.40 per hour – and only two of these had good outcomes. Even after exclusions and adjustments, the association with adverse outcomes continued.
“As cooling is now the standard treatment for neonatal encephalopathy, it is important to avoid an abnormally increased supply of inspired oxygen during and after resuscitation,” the research team wrote.
Commenting on the findings, senior investigator Dr. Marianne Thoresen, also of the University of Bristol, told Reuters Health by email that the data were obtained before the introduction of new guidelines in 2010.
The new guidelines, she said, “suggest that newborn infants should initially be resuscitated in air, not oxygen. It is only when the baby does not respond to air one should add oxygen and mix it with air, not give 100% O2 as one often did before.”
“It is only when there is a disease in the lung, like if the baby has aspirated meconium into the lung, one needs to give high fraction of oxygen.”
“So in practice,” she concluded, “if you have a sick baby after a problematic delivery you can protect the brain from developing injury by cooling it down for three days — and you can damage it by giving 100% oxygen.”
J Pediatr 2012.