Increased Inspired Oxygen in the First Hours of Life is Associated with Adverse Outcome in Newborns Treated for Perinatal Asphyxia with Therapeutic Hypothermia

OBJECTIVE: To assess whether increased inspired oxygen and/or hypocarbia during the first 6 hours of life are associated with adverse outcome at 18 months in term neonates treated with therapeutic hypothermia.

STUDY DESIGN: Blood gas values and ventilatory settings were monitored hourly in 61 newborns for 6 hours after birth. We investigated if there was an association between increased inspired oxygen and/or hypocarbia and adverse outcome (death or disability by Bayley Scales of Newborn Development II examination at 18-20 months).

RESULTS: Hypothermia was started from 3 hours 45 minutes (10 minutes-10 hours) and median lowest Pco(2) level within the first 6 hours of life was 30 mm Hg (16.5-96 mm Hg). The median highest fraction of inspiratory oxygen within the first hour of life was 0.43 (0.21-1.00). The area under the curve fraction of inspiratory oxygen and Pao(2) for hours 1-6 of life was 0.23 (0.21-1.0) and 86 mm Hg (22-197 mm Hg), respectively. We did not find any association between any measures of hypocapnia and adverse outcome (P > .05), but increased inspired oxygen correlated with adverse outcome, even when excluding newborns with initial oxygenation failure (P < .05).

CONCLUSION: Increased fraction of inspired oxygen within the first 6 hours of life was significantly associated with adverse outcome in newborns treated with therapeutic hypothermia following hypoxic ischemic encephalopathy.