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We owe the development of clinical phototherapy to an astute observation made, more than 50 years ago, by Sister J. Ward, the nurse in charge of the premature baby unit at the former Rochford General Hospital in Essex, England.1 As described by Dobbs and Cremer, Sister Ward recognized the value of sunshine and fresh air to all, including premature babies, and she would take the “more delicate infants out into the courtyard, sincerely convinced that the combination of fresh air and sunshine would do them much more good than the stuffy, overheated atmosphere of the incubator.”1 During a ward round in 1956, Sister Ward showed the pediatricians a jaundiced, premature infant who appeared pale yellow except for a triangle of skin that was much yellower than the rest of the body. Apparently, a corner of the sheet had covered this part of the baby and the Sister recognized that the rest of the baby had been “bleached” by the sun. (It was only recognized more than a decade later that the mechanism for the bleaching of yellow serum and skin—photooxidation—probably plays a minor role in the reduction of the serum bilirubin concentration in newborns treated with phototherapy.)2,3

A few weeks later, in the same nursery, a tube of blood, inadvertently exposed to sunlight for several hours, showed a total serum bilirubin (TSB) level of 10 mg/dL, much lower than anticipated.1 This led to the hypothesis that visible light could affect serum bilirubin levels in vivo and the concept of using phototherapy as a clinical tool was born.4 Cremer et al. then showed that exposing jaundiced infants either to sunlight or to blue fluorescent lights effectively lowered their bilirubin levels.4 Although the observations of Cremer et al. were published in 1958 and confirmed in multiple subsequent publications in Europe and Central and South America, it was not until Lucey et al. published their findings in 19685 that this simple, apparently safe, and effective treatment for hyperbilirubinemia achieved widespread acceptance in the United States and phototherapy is now used worldwide. Although there exists a vast body of literature from human, animal, and laboratory investigation dealing with the mechanism of action, biological effects, complications, and clinical use of phototherapy, there is a need for additional information on how phototherapy works, how its dosage should be measured, and how it should be administered most effectively. Jährig et al. provide a reference source on phototherapy data up to 19936 and the recent, remarkably comprehensive and critical review by the National Institute for Health and Clinical Excellence (NICE) in the United Kingdom is an excellent resource for additional reading.7

Mechanism of Action

Phototherapy is a mechanism for detoxifying bilirubin and lowering the TSB level. It achieves this by using light energy to change the shape and structure of bilirubin, converting it to molecules that can be excreted even when normal conjugation ...

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