Do Hyperoxaemia and Hypocapnia Add to the Risk of Brain Injury After Intrapartum Asphyxia?

Abstract

It is difficult to maintain a proper balance between hyperoxemia and hypoxemia, and between hypocapnia and hypercapnia, when resuscitating severely asphyxiated infants. Hyperoxemia may be especially dangerous to the brainduring reperfusion after severe asphyxia. Infants with postasphyxia hypoxic ischemic encephalopathy (HIE) frequently have episodes of hyperoxemia and/or hypocapnia in the first hours of life. A retrospective cohort study was planned to determine whether such episodes, occurring in the first 2 postnatal hours, heighten the risk of brain injury after intrapartum asphyxia. Adverse outcomes at age 2 years included death, severe cerebral palsy, or any degree or cerebral palsy accompanied by blindness, deafness, or delayed development. Severe and moderate hyperoxemia were defined as a PaO 2 greater than 200 and 100 mm Hg, respectively. Severe and moderate hypocapnia were defined as a PaCO 2 less than 20 and 25 mm Hg. Of 218 infants whose outcomes were known, 127 (58%) had adverse outcomes. There were 64 deaths and 63 severe neurodevelopmental deficits. In 139 infants with blood gas data available, multivariate analysis showed that, in the first 20 to 120 minutes after birth, severe hyperoxemia was significantly associated with adverse outcomes (odds ratio [OR], 3.85; 95% confidence interval [CI], 1.67-8.88). Any occurrence of severe hypocapnia also was significantly associated with adverse outcomes (OR, 2.34; 95% CI, 1.02-5.37), but outcomes did not correlate with moderate hypocapnia. Infants with both severe hyperoxemia and severe hypocapnia were the likeliest to have an adverse outcome (OR, 4.56; 95% CI, 1.4-14.9). Severe hyperoxemia in a severely asphyxic infant is associated with adverse outcomes at age 2 years, and the risk increases if severe hypocapnia also is present. These findings suggest that close monitoring and individualized oxygen supplementation and ventilation will maximize the chances of maintaining normoxia and normocapnia.