Oxidative imbalance in preterm resuscitation with different oxygen concentrations

Newborns and specially the preterm ones are probably more prone to oxidative stress than later in life. Hyperoxic exposure used for resuscitation of preterm infants, although essential for their survival, probably induces excessive production of reactive oxygen metabolites in the respiratory system; the consequent oxygen toxicity is thought to be an important factor in the pathogenesis of chronic lung disease, causing lung injury and resulting in the release of multiple proinflammatory cytokines and production of extracellular matrix components and growth factors. Biochemical evidence of oxygen toxicity persists even after very short periods of oxygen supplementation at birth in preterm newborns. Furthermore, exposure to oxygen or to oxidative stress in very premature infants (who have very low antioxidant defenses), provokes the initial inflammatory signs of respiratory distress syndrome. The present study had as primary outcome the evaluation of oxidative imbalance on 60 preterm infants (gestational age :32 weeks) divided in a random manner into three groups according to different concentrations of oxygen administered at birth for resuscitation according to new AAP guidelines group 1: 100% oxygen; group 2: 60% oxygen; group 3: group 1: 40% oxygen). Oxygen delivery were adjusted to mantain oxygen concentration about 90-95%. Blood samples were collected before treatment, and after 24 and 72 hours and after 7 days, to evaluate the circulating levels of carbonylated and nitrosylated proteins, catalase, gluthatione peroxidase, superoxide dismutase and thiol groups. We found no difference in mortality among these three groups but the occurrence of bronchopulmonary dysplasia resulted only represented in the group of infants resuscitated with 100% oxygen. The same newborns had longer ventilation and hospitalization time and higher incidence of pneumothorax. In our study we have found a significant time-dependent increase in oxidized proteins expecially in preterm resuscitated with 100% oxygen. However, the altered serum levels of antioxidant enzymes demonstrated an oxidative imbalance for all oxygen treatments