THE EFFECT OF SPECTRAL IRRADIANCE ON THE ISOMERIZATION OF BILIRUBIN IN VIVO

The initial event during phototherapy is the isomerization of native bilirubin to more polar configurational isomers (Z,E) and a structural isomer called lumirubin (LUM). The purpose of this study was to compare the effect of narrow spectrum blue light (B) versus broad spectrum white light (W) on the production of photoisomers in jaundiced infants. Thirteen preterm neonates (BW 1.68 ± .45 kg, GA 32 ± 2.3 wks) were studied under both B and W light. Irradiance at 450 nm was controlled at 12 uwatt/cm2/nm for both B and W. Infants were assigned to one of two study orders: B,W,B (n=4) or W,B,W (n=9). Each light condition (B or W) was administered for 12 hrs. Serum for Z,E and LUM were obtained before treatment and every 12 hours thereafter. Results were expressed as a percent of the total bilirubin. For all study infants % Z,E and LUM under B were compared with % under W for the two possible treatment sequences: W to B and B to W