Abstract
Although phototherapy with blue or cool white fluorescent light is widely employed for neonatal hyperbilirubinemia, its effect on substances other than bilirubin, is largely unknown. The function of human platelets (platelet rich plasma) exposed in vitro for up to 170 minutes to blue or cool white fluorescent light (8 20 wt lamps) was studied. Within 110 minutes, blue light (1,908 uwt/cm2) inhibited platelet aggregation by ADP and connective tissue suspension, and resulted in platelet loss of ADP, ATP, and glgcogen. Electron micrographs revealed these platelets to be less dense than normal, depleted of glycogen granules and organelles, and to have ill-defined membranes. Platelet injury could be enhanced by adding a photosensitizing agent, hematoporphyrin, to platelet samples before exposure. In contrast to blue light, cool white light (2,670 uwt/cm2) had no effect on platelet aggregation unless platelet samples contained hematoporphyrin. Platelets kept in the dark for 170 minutes maintained their integrity.
These results indicate that platelets are damaged in vitro when exposed to amounts of blue light used in phototherapy. Results suggest that cool white light may be safer than blue for newborns.
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Maurer, H., Haggins, J. & Still, W. PLATELET INJURY BY LIGHT. Pediatr Res 8, 405 (1974). https://doi.org/10.1203/00006450-197404000-00393
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DOI: https://doi.org/10.1203/00006450-197404000-00393