Abstract 1104 Poster Session IV, Tuesday, 5/4 (poster 362)

Gallium nitride LEDs produce high intensity, narrow spectrum light that overlaps the absorption spectrum of bilirubin (BR). We have shown that these light sources effectively photodegrade BR in vitro (Pediatr Res 1998:44:804-9). Using genetically jaundiced, neonatal Gunn rats, we now evaluated in vivo LED light efficacy through measurements of plasma BR (PBR). Light safety was assessed through measurements of total body carbon monoxide (CO) excretion (VeCO) because we have shown that not only is heme catabolism the major component of VeCO, but that oxidative injury can also generate CO, which is reflected in elevated VeCO. Pups, 36 - 60h old, were studied in chambers closely surrounded by each light source and supplied with air for VeCO measurements. Control pups were kept in the dark, others exposed for 4h with either: devices with 40 blue, blue-green, green, or white LEDs; BiliBlanket (Ohmeda); or two cool-white and one special blue fluorescent tubes (FT). Post-PT, animals were sacrificed and blood collected for PBR quantitation with a UB Analyzer. Efficacy is expressed as the % of PBR lost compared to controls. Safety is expressed as % difference in VeCO before PT and 30 min after commencement of PT. (Table)

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Full size table

These in vivo results support our previous in vitro finding that of the LEDs, blue LED light was most effective in PBR removal. Even though the efficacy of the BiliBlanket and FT (360° light exposure, close contact) approached that of the blue LED, it is not appropriate to relate this finding to the clinical setting because of the conventional device size and proximity limitations. LEDs in contrast can be used in close body contact to deliver high intensity light to an unlimited surface area and shape. In addition, the higher VeCO values indicate greater potential photosensitization with the conventional PT devices. Consequently, we conclude that blue LED light is both safe and effective for PT.