Background: Newborn infants are exposed to high levels of oxidative stress after birth. On the other hand, their anti-oxidant system is still immature and limited. Bilirubin is known to have both neurotoxicity and anti-oxidative capacity. However, the significance of ‘physiological’ hyperbilirubinemia in the early neonatal period is not well understood.
Objectives: To study relationship between indices of oxidant/anti-oxidant status and bilirubin (and other potential anti-oxidative substances) in the plasma in preterm infants in the early neonatal period.
Methods: Subjects are preterm infants < 36 weeks of gestation without major complications born and managed at neonatal units of Tokai University Hospital in Nov 2016-Mar 2017. Total bilirubin (TB), unbound bilirubin (UB), total hydroperoxides (TH; oxidants), redox potential (RP; anti-oxidant potential), anti-oxidative capacity (RP/TH) in the plasma were assayed using FRAS4 system (WismerllTM) on day0 (at birth), 1 and 2. Daily changes and inter-correlations of these variables were studied. Correlations between TH, RP and RP/TH and gestational age (GA), blood hemoglobin, plasma albumin or uric acid (UA) were also studied.
Results: The number of subjects were 19 (8 males/11 females). Their gestational ages were 27.0-35.9 (median 34.3) weeks and birth weights were 702-2946 (median 1968) grams.
TB, UB and TH increased according to postnatal days. There were no correlations between bilirubin values and indices of oxidant/anti-oxidant status. However, changes in both RP and UA from day0 to day1 were inversely correlated with GA. The Change in RP from day0 to day1 was positively correlated with the change in UA from day0 to day1.
Conclusions: Levels of oxidants in preterm newborn infants were relatively low compared to adult reference values, which increased gradually after birth. Contribution of bilirubin as anti-oxidant was not evident.