Bilirubin isomers during LED phototherapy of hyperbilirubinemic neonates, blue-green (~478 nm) vs blue

BACKGROUND: The clinical part of this randomized controlled trial concerning phototherapy of neonates with hyperbilirubinemia showed that the recommended blue-green LED light (≈478 nm) was 31% more efficient than standard blue LED light (≈459 nm) measured by the decline in total serum bilirubin. Lumirubin has biologic effects. The aim was to compare the serum bilirubin isomers, efficacy, and biologic effects between the two phototherapy groups.

METHODS: Inclusion criteria: neonates healthy except for hyperbilirubinemia, gestational age ≥33 weeks, birth weight ≥1800 g, and postnatal age >24 h. Forty-two neonates were randomized to receive overhead blue-green light and 44 blue light. Treatment 24 h. The light irradiance was equal.

RESULTS: The percentage decrease of combined bilirubin isomers was 47.8% for blue-green light vs 33.4% for blue light, the ratio being 1.43. Corresponding values for Z,Z-bilirubin were 55.6% vs 44.2%, the ratio being 1.26. The increase in the absolute serum concentrations of the photoisomer Z,E-bilirubin and thereby combined photoisomers were greater using blue light.

CONCLUSION: Blue-green light was essentially more efficient determined by the decline of combined bilirubin isomers and Z,Z-bilirubin itself. Regarding biological effects neonates receiving blue-green light might be more affected than neonates receiving blue light.

IMPACT: Phototherapy of hyperbilirubinemic neonates using blue-green LED light with a peak emission of 478 nm was 43% more efficient than standard blue LED light with a peak emission of 459 nm was measured by the decline of serum combined bilirubin isomers, and the decline of toxic Z,Z-bilirubin was 26% greater. Apparently, there was a discrepancy between the huge drop in total serum bilirubin and the low serum concentrations of E,Z-bilirubin and E,Z-lumirubin. This was caused by the rapid excretion of E,Z-lumirubin. Lumirubin has biologic effects. Due to greater lumirubin production neonates exposed to blue-green light might be more affected than those exposed to blue light.