Elsevier

Seminars in Perinatology

Volume 28, Issue 5, October 2004, Pages 326-333
Seminars in Perinatology

Phototherapy: Current methods and future directions

https://doi.org/10.1053/j.semperi.2004.09.003Get rights and content

Phototherapy is the most common therapeutic intervention used for the treatment of hyperbilirubinemia. Although it has become a mainstay since its introduction in 1958, a better understanding of the photobiology of bilirubin, characteristics of the phototherapy devices, the efficacy and safety considerations of phototherapy applications, and improvements in spectroradiometers and phototherapy devices are necessary for more predictable and improved clinical practices and outcomes. A step forward in instituting consistent, uniform, and effective use of phototherapy is the recent American Academy of Pediatrics clinical guideline on the management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation, which outlines a clinical strategy for the diagnosis of hyperbilirubinemia and contains direct recommendations for the application of phototherapy. This article reviews the parameters that determine the efficacy of phototherapy, briefly discusses current devices and methods used to deliver phototherapy, and speculates on future directions and studies that are still needed to complement our presently incomplete knowledge of the facets of this common mode of therapy.

Section snippets

Photobiology of bilirubin

The rate of removal of unconjugated bilirubin from the body during phototherapy depends on the following three related processes: (1) the rate of bilirubin photoalteration; (2) the transport of photoproducts from the skin to the circulation; and (3) the excretion of these photoproducts by the liver and kidney.2, 5, 6 Of these processes, the photoalteration of bilirubin (Fig. 1) is a complex set of photochemical reactions and believed to be the rate-limiting step in the elimination of bilirubin

Efficacy

The therapeutic efficacy of phototherapy is dependent primarily on the following factors: the spectral qualities of the delivered light (wavelength range and peak),b intensity of light (irradiance), exposed body surface area (BSA), skin thickness and pigmentation, the total bilirubin at clinical presentation, and duration of exposure.

Spectral qualities

The optimum light quality for the most efficient use of phototherapy is still under active investigation and discussion.5, 9 The yellow bilirubin absorption spectrum in plasma and in buffer/human serum albumin has been well established. In general, the in vitro bilirubin light absorption spectrum is used as the basis for the design of phototherapy light sources. Thus, the most effective light sources for degrading bilirubin in the skin and the circulation are those that emit light in a

Irradiance

Irradiance or light intensity refers to the number of photons as directed to or received per square cm of the exposed BSA. Because the irradiance is quantitated as μW/cm2 within the effective wavelength range for efficacy, it is also referred to as “spectral irradiance” and is expressed as μW/cm2/nm.13 “Deliverable spectral irradiance” is different for each type of light source, and is dependent on the its design and the distance between the light source and patient in an inverse square root

Exposed surface area

Effective phototherapy is very much dependent on exposure to the largest BSA of the newborn. The greater the area exposed, the greater the rate of total bilirubin decline.15 At present, the limited BSA exposure by all light sources is the greatest impediment to effective phototherapy. In general, with the present overhead and underneath devices used singly, only up to 30% of BSA is exposed to light. The variability and limitation is attributable to the dimensions of a device’s light footprint

Skin thickness and pigmentation and initial total bilirubin level

Patient parameters, such as increases skin thickness (ie, in older Crigler-Najjar patients)17 and highly pigmented skin, have been reported to impede effective phototherapy.18 Furthermore, the initial total bilirubin level as well as an imbalance between bilirubin production and elimination also negatively affects phototherapy efficacy.19

Duration of exposure

Although duration of exposure to elevated total bilirubin levels could be an important factor in understanding risk for acute bilirubin encephalopathy or kernicterus, information about the duration of bilirubin exposure is generally lacking in the literature. Moreover, most of the literature addressing risk has been focused on peak total bilirubin levels. This limited perspective may need to be broadened to include the duration of exposure to total bilirubin or its fractions and is discussed

Side effects

More effective phototherapy probably represents less risk for the newborn, assuming that, in the photochemical reactions, the light does not affect molecules other than bilirubin. This latter possibility is one that should be explored more seriously for smaller, less mature and more translucent newborns, who are often treated with photosensitizing drugs, such as riboflavin (RF), Vitamin K, and others. RF, a powerful endogenous photosensitizer, which has been extensively studied, decreases

Current light sources

There is a considerable selection of various custom-made and commercial phototherapy devices, which have been produced for investigative and clinical applications. However, a complete discussion of these is beyond the scope of this review. In summary, phototherapy devices can be categorized by their light source as follows: (1) fluorescent tube (TL12, 60 cm, 20W) devices with different colors of light [cool white (CW), blue, special blue (BB, 52, and 03), turquoise, or green] of straight or

“Blue hue” effect

Blue light may be most therapeutic for jaundiced infants, but caregivers have reported a range of “irritations” from the use of blue fluorescent tubes, including headaches, nausea, and vertigo.31 Initially, it was thought that the direct current (DC)-powered, LED-based devices would be free of such effects because this light does not “flicker” at 50 to 60 Hz/sec, as do AC-powered fluorescent tubes. This appears not to be the case and the true cause for the visual irritation is more likely due

Conclusions

In conclusion, phototherapy is one of the most common medical interventions with well-established efficacy and probably safety for most short-term applications in near-term and term infants with neonatal hyperbilirubinemia. There has been recent clarification of management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation with the publication of the AAP guideline with direct recommendations for the application of phototherapy. Nonetheless, a better understanding of the

Acknowledgments

This work was supported by unrestricted gifts from the H.M. Lui Research Fund, the Hess Research Fund, and the Mary L. Johnson Research Fund.

References (47)

  • A.F. McDonagh

    PhototherapyFrom ancient Egypt to the new millennium

    J Perinatol

    (2001)
  • A.F. McDonagh et al.

    Phototherapy and the photobiology of bilirubin

    Semin Liver Dis

    (1988)
  • Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation

    Pediatrics

    (2004)
  • D.A. Lightner et al.

    Bilirubin photooxidation products in the urine of jaundiced neonates receiving phototherapy

    Pediatr Res

    (1984)
  • J.F. Ennever et al.

    Rapid clearance of a structural isomer of bilirubin during phototherapy

    J Clin Invest

    (1987)
  • G. Agati et al.

    Configurational photoisomerization of bilirubin in vitro. II. A comparative study of phototherapy fluorescent lamps and lasers

    Photochem Photobiol

    (1985)
  • F. Ebbesen et al.

    Phototherapy with turquoise versus blue light

    Arch Dis Child Fetal Neonatal Ed

    (2003)
  • M.L. Chan et al.

    In vivo efficacy of light-emitting diodes (LEDs) as a light source for phototherapy in neonatal jaundiced rats

    Pediatr Res

    (1999)
  • D.S. Seidman et al.

    A prospective randomized controlled study of phototherapy using blue and blue-green light-emitting devices, and conventional halogen-quartz phototherapy

    J Perinatol

    (2003)
  • M.J. Maisels

    PhototherapyTraditional and nontraditional

    J Perinatol

    (2001)
  • K.L. Tan

    The pattern of bilirubin response to phototherapy for neonatal hyperbilirubinaemia

    Pediatr Res

    (1982)
  • J.H. Kang et al.

    Double phototherapy with high irradiance compared with single phototherapy in neonates with hyperbilirubinemia

    Am J Perinatol

    (1995)
  • P.L. Jansen

    Diagnosis and management of Crigler-Najjar syndrome

    Eur J Pediatr

    (1999)
  • Cited by (0)

    View full text