[Light therapy of newborns with hyperbilirubinemia].

In a significant fraction of newborns the skin becomes yellow for a few days after birth due to accumulation of bilirubin, a product of heme catabolism. If the concentration of bilirubin in the serum approaches the binding capacity of albumin, bilirubin may penetrate into the central nervous system and cause irreversible damage. Phototherapy is the most common form of therapy, used on 5-10% of all newborns in Norway. Three photochemical reactions are of importance in this treatment: Photooxydation of bilirubin followed by fragmentation of the molecule and formation of water-soluble products. Reversible formation of (4Z,15E) and (less important) (4E,15Z) configurational isomers. Irreversible formation of the structure isomer Z-lumirubin, which is relatively water-soluble and can be excreted. The (4E,15Z) isomer is probably an intermediate in the formation of Z-lumirubin, whose formation therefore requires the absorption of two photons. Irreversible formation of Z-lumirubin, which has a quantum yield that increases with increasing wavelength of the light, is believed to be the most important reaction in phototherapy. All known side-effects of phototherapy are transient and not serious.