Dermal bilirubin kinetics during phototherapy in term neonates

Aim: To investigate dermal bilirubin kinetics during phototherapy in the presence of neonatal indirect hyperbilirubinaemia. Methods: 33 neonates with non-haemolytic indirect hyperbilirubinaemia, who required phototherapy, were included in the study. Phototherapy modules containing four normal and four blue fluorescent lamps were used during the study. The transcutaneous bilirubin index (TcBI) was measured in an area of the forehead covered by a 2.5 cm diameter opaque patch and a nearby exposed site. The TcBI obtained from patched and unpatched areas and simultaneous serum bilirubin (SB) concentrations were measured before the start of phototherapy and after 6, 12, 18, 30, 42 and 66 h of phototherapy. Results: SB concentration and the TcBI from the unpatched area decreased significantly during the first 6 h of exposure, while the TcBI obtained from the patched area decreased significantly after 12 h. The TcBI from the unpatched area was consistently lower than that from the patched area during phototherapy. After the onset of phototherapy, there was a weak, non-significant correlation between SB concentrations and the TcBI from patched and unpatched areas. Conclusion: Phototherapy was effective for both patched and unpatched areas, but the rate of decline was slower in patched areas, only becoming significant in the second 6 h of treatment. There was no significant correlation between the levels of SB and TcBI after the onset of phototherapy, and therefore the use of TcBI cannot be recommended as a surrogate measure of SB.