Background Phototherapy is the mainstain of treatment for neonatal jaundice. Photoisomers are more polar than native bilirubin IX-alpha (z, z) and can be excretedinbileandurine without conjugation. Rapid formation of PI may be an important component of the crash-cartapproach to extreme NJ.

Objective To compare the rate and degree of photoisomerization during intensive phototherapy using single or double banks of fluorescent lights vs a single bank of photodiodes.

Design and methods: The study was approved by the regional research ethics committee. 42 newborn infants due to receive phototherapy for NJ according to Norwegian national guidelines. Enrolled by written informed consent from the parents. Infants were randomly to one of 3 groups:

1. single unit phototherapy with fluorescent lights

2. double unit fluorescent phototherapy;

3. single unit photodiode. Irradiance was measured on the back and flanks.

Blood was drawn at 0, 15, 30, 60,120, and240 minutes. Total serum bilirubin was analyzed by cooximetry. Serum samples were frozen and analyzed for photoisomers by HPLC. Data were analyzed using Anova and t-tests.

Results Irradiance was significantly higher using double fluorescent lights vs single fluorescent and photodiodes (40.4 p<0.05 for double vs single fluorescent and single photodiodes, measured on the back). 2-way Anova was highly significant for increase of PI over time (p<0.0001), and significant for group differences (p<0.05).

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Abstract 1348 Figure 1

Study Groups

Formation of PI reached 25% at 4h, anddid not appear to have plateaued.

Conclusions Formation of PI is rapid during intensive phototherapy. However, increasing irradiance or chancing the character of thelight source did not significantly improve the rate or level of PI formation.