Fundamentals Of Phototherapy For Neonatal Jaundice

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ANC200224.qxp8/24/113:03 AMPage 10Originally published in the December 2006 issue of Advances in Neonatal Care. This version has been revised and updated August 2011by the author.Fundamentals of Phototherapy forNeonatal JaundiceLaura A. Stokowski, MS, RNABSTRACTPhototherapy is the use of visible light for the treatment of hyperbilirubinemia in the newborn. This relatively commontherapy lowers the serum bilirubin level by transforming bilirubin into water-soluble isomers that can be eliminatedwithout conjugation in the liver. The dose of phototherapy is a key factor in how quickly it works; dose in turn is determined by the wavelength of the light, the intensity of the light (irradiance), the distance between the light and the baby,and the body surface area exposed to the light. Commercially available phototherapy systems include those that deliverlight via fluorescent bulbs, halogen quartz lamps, light-emitting diodes, and fiberoptic mattresses. Proper nursing careenhances the effectiveness of phototherapy and minimizes complications. Caregiver responsibilities include ensuringeffective irradiance delivery, maximizing skin exposure, providing eye protection and eye care, careful attention tothermoregulation, maintaining adequate hydration, promoting elimination, and supporting parent-infant interaction.KEY WORDS: bilirubin, hyperbilirubinemia, jaundice, neonatal intensive care, newborn, phototherapy, premature infantPhototherapy is the use of visible light for thetreatment of hyperbilirubinemia, or jaundice,in the newborn.1 It is perhaps the most common nonroutine therapy applied in the newbornpopulation. How phototherapy came to be is a fascinating story, with a nurse at its center.2Sister Ward, the nurse in charge of the PrematureUnit at Rochford General Hospital in Essex, England,firmly believed in the restorative powers of fresh airand sunshine (Figure 1). On sunny days, she wouldwheel the infants outdoors into the hospital courtyard, returning them to the nursery just before thedoctors—who were not as keen on this practice—arrived for ward rounds. One day in 1956, SisterWard showed the physicians an undressed infantwhose skin was pale except for a triangular area thatappeared much yellower than the rest of its body.Author Affiliations: Inova Fairfax Hospital for Children, FallsChurch, VirginiaCorrespondence: Laura A. Stokowski, MS, RN, 8317 ArgentCircle, Fairfax Station, VA 22039 (stokowski@cox.net).Copyright 2011 by The National Association ofNeonatal NursesDOI: 10.1097/ANC.0b013e31822ee62cS10Dr R. H. Dobbs asked her if she had painted thebaby’s skin with iodine. She denied having done so,telling him that what she held in her arms was a jaundiced infant whose color had faded except in an areathat had been covered by the corner of a sheet.2Subsequently, physicians and scientists at RochfordHospital discovered that the levels of bilirubin pigment in tubes of blood left sitting in the sun alsodropped dramatically. Putting these observationstogether, the idea of phototherapy for neonatal jaundice was born. The very first phototherapy unit incorporating an artificial light source instead of naturalsunlight was devised and tested by Cremer et al3 atRochford Hospital, and the results were reported inThe Lancet, in 1958 (Figure 2).Phototherapy was not used in the United Statesuntil the landmark study of Lucey et al4 was published in Pediatrics a full decade later. This randomized controlled trial demonstrating the effectivenessof phototherapy led to its acceptance as a simple,inexpensive, and relatively safe way to preventhyperbilirubinemia in premature infants.NORMAL BILIRUBIN METABOLISMHumans continuously form bilirubin, and newborninfants produce relatively more bilirubin than anyAdvances in Neonatal Care Vol. 11, No. 5S pp. S10-S21Copyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxp8/24/113:03 AMPage 11Fundamentals of Phototherapy for Neonatal JaundiceFIGURE 1.Miss Jean Ward, in 1956, with one of the earliestinfants given phototherapy at Rochford GeneralHospital. Courtesy of BMJ Publishing Group.other age group. The typical bilirubin load of thenewborn is quite high, 2 to 3 times that of an adult.Bilirubin is a product of the normal destruction of circulating erythrocytes (which have a shortened lifespan in the newborn infant) and increased turnover ofcytochromes.5 Some infants have excessive bilirubinproduction, and a correspondingly elevated load ofunconjugated bilirubin (Table 1).Unconjugated bilirubin is lipid-soluble and mustbe transported to the liver in the plasma, boundreversibly to albumin.6 In the liver, bilirubin is transported across hepatic cell membranes, where it bindsto ligandin for conjugation. A liver enzyme, uridinediphosphoglucuronate glucuronosyltransferase, conjugates bilirubin, converting it to water-soluble bilirubin pigments that can be excreted into the bile andexit the body via the intestines, or, to a lesser degree,filtered through the kidneys (Figure 3). Bilirubin pigments in the gut that are not eliminated can be reabsorbed into the circulation as unconjugated bilirubin,S11FIGURE 2.The first artificial light apparatus devised for cradleillumination of infants at Rochford General Hospital.The hemicylindrical stainless steel reflector, suspendedon a height-adjustable moveable gantry, containseight 24-in light blue 40-W fluorescent tubes spaced2 in apart. A cot can be wheeled underneath thereflector, and the lights can be switched on separatelyto vary the amount of power delivered.3 Reprintedwith permission.essentially recycling the bilirubin load, a processcalled enterohepatic recirculation. Thus, babies withreduced conjugation or elimination of bilirubin arealso at risk for hyperbilirubinemia (Table 1). A moredetailed explanation of newborn bilirubin metabolism can be found in an article in the April 2002 issueof this journal.7HOW PHOTOTHERAPY WORKSPhototherapy converts bilirubin that is present in thesuperficial capillaries and interstitial spaces of theskin and subcutaneous tissues to water-soluble isomers that are excretable without further metabolismby the liver (Figure 4). Neonatal jaundice expertMaisels suggests that phototherapy is much like apercutaneous drug.6,8 When phototherapy illuminates the skin, an infusion of discrete photons ofenergy are absorbed by bilirubin much like a drugmolecule binds to a receptor. Bilirubin molecules inlight-exposed skin undergo relatively quick photochemical reactions—configurational isomerization,Advances in Neonatal Care Vol. 11, No. 5SCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxp8/24/11S123:03 AMPage 12StokowskiTABLE 1. Mechanisms of Hyperbilirubinemia(1a) Increased Bilirubin Production(1b) Impaired Conjugation or ExcretionHemolytic disease of the newbornInadequate or poor feeding intake Rh isoimmunization Prematurity ( 39 weeks) ABO incompatibility Delayed or impaired lactogenesis Minor blood group incompatibility Inadequate milk transfer Other feeding disordersPolycythemiaIncreased enterohepatic circulation Intestinal obstruction Meconium ileus Meconium plugging Cystic fibrosisRed blood cell enzyme disordersHormonal deficiencies G6PD deficiency Hypothyroidism Pyruvate kinase deficiency HypopituitarismRed blood cell membrane defectsDisorders of bilirubin metabolism Hereditary spherocytosis Crigler-Najjar syndrome I and II Gilbert disease Lucey-Driscoll syndromeBirth trauma Vacuum or instrumented delivery Bruising Cephalohematoma or subgaleal bleedNeonatal infection Urinary tract infection SepsisEthnicity Asian ethnic backgroundstructural isomerization, and photooxidation—toform nontoxic, excretable isomers. These bilirubinisomers have different shapes than the native isomer,are more polar, and can be excreted from the liverinto the bile without undergoing conjugation orrequiring special transport for their excretion.9Urinary and gastrointestinal elimination remainimportant to the process of reducing the bilirubinload.WHEN IS PHOTOTHERAPY PRESCRIBED?The aim of phototherapy is to curtail rising serumbilirubin and prevent its toxic accumulation in thebrain, where it can cause the serious, permanentneurological complication known as kernicterus.Where the technology is readily available, phototherapy has nearly abolished the need forexchange transfusion to treat hyperbilirubinemia.Phototherapy is typically used either prophylactically or therapeutically. In preterm infants or those with a knownhemolytic process, it is often used prophylactically, to prevent a significant rise in serumbilirubin. In late-preterm and full-term infants, it is administered at therapeutic doses to reduce excessivebilirubin levels and avoid development ofbilirubin encephalopathy.The photoisomerization of bilirubin begins almostinstantaneously when the skin is exposed to light.8Unlike unconjugated bilirubin, the photoproducts ofthese processes are not neurotoxic.8 Therefore, the mostimportant intervention for the severely hyperbilirubinemic infant is to initiate phototherapy without delay.www.advancesinneonatalcare.orgCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxp8/24/113:03 AMPage 13Fundamentals of Phototherapy for Neonatal JaundiceS13FIGURE 3.Neonatal bilirubin metabolism. From Stokowski.7 Reprinted with permission.THE IMPORTANCEOFDOSEA robust relationship exists between the dose of phototherapy and the rate of decline in serum bilirubinlevel.8 Dose of phototherapy is determined by severalkey factors: Spectral qualities of the light source used (wavelength range and peak); Intensity of the light (irradiance); Distance between the light and the infant’s skin; Body surface area exposed by the irradiatedfield or “footprint.”Spectral QualitiesThe most effective light sources for degrading bilirubin emit light in a relatively narrow wavelengthrange (400 to 520 nanometers, or nm), with a peak of460 10 nm.1 At these wavelengths, light penetratesthe skin well and is maximally absorbed by bilirubin.8 Blue, green, and turquoise light (the blue-greenspectrum) are considered the most effective, andsome evidences suggest that given equal irradiancelevels, the turquoise spectral range is more efficientin reducing bilirubin than blue because of greaterskin penetration.9Advances in Neonatal Care Vol. 11, No. 5SCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxpS148/24/113:03 AMPage 14StokowskiFIGURE 4.way to increase irradiance is to move the light closerto the infant. Caution must be exerted when positioning halogen phototherapy lamps, which cannotbe positioned closer to the infant than recommendedby their manufacturers without incurring the risk fora burn.11Exposed Body Surface AreaThe mechanism of phototherapy. When bilirubin molecules absorb light, 2 main photochemical reactionsoccur: Native 4Z, 15Z-bilirubin converts to 4Z, 15Ebilirubin (also known as photobilirubin) and to lumirubin. Unlike 4Z, 15Z bilirubin, photobilirubin can beexcreted via the liver without conjugation, but itsclearance is very slow and its conversion is reversible.In the bowel (away from the light), photobilirubin isconverted back to native bilirubin. Lumirubin is notreversible. So, although much less lumirubin thanphotobilirubin is formed, lumirubin is cleared from theserum much more rapidly, and it is likely that lumirubinformation is primarily responsible for the decline inserum bilirubin that results from phototherapy. Smallamounts of native bilirubin are also oxidized tomonopyrroles and dipyrroles that can be excreted inthe urine. This is a slow process and only a minorcontributor to the elimination of bilirubin duringphototherapy. Diagram courtesy of Mary Puchalski.A popular, but mistaken belief holds that phototherapy delivers ultraviolet light. The phototherapysystems currently used for newborn infants do notemit significant amounts of ultraviolet radiation.8The greater the body surface area exposed to light,the faster the decline in serum bilirubin. Many lightsources used in neonatal care do not expose a sufficient area of skin to the light. The light source mayhave an adequate spectral irradiance in the center ofthe light’s footprint; however, irradiance decays significantly at the periphery of the light.12 The result isthat only an insufficient proportion of the infant’sbody surface area receives effective treatment. Thisproblem can be solved by positioning the infantproperly within the footprint of the light or usingmultiple light sources for coverage of at least 80% ofthe body surface13 (Figure 5).The size of the exposed body surface area, alongwith the level of irradiance, determines the spectralpower of the phototherapy application, which in turninfluences its effectiveness.14 The larger the exposedbody surface and stronger the light, the higher thespectral power.COMPARING AND CONTRASTINGPHOTOTHERAPY DELIVERY SYSTEMSA number of different light sources are commercially available for neonatal phototherapy. Each hasits own advantages and disadvantages. DifferentFIGURE 5.IrradianceIrradiance is the light intensity, or number of photonsdelivered per square centimeter of exposed body surface. The delivered irradiance determines the effectiveness of phototherapy; the higher the irradiance,the faster the decline in serum bilirubin level.10Spectral irradiance, quantified as W/cm2/nm,varies with the design of the light source. It can bemeasured with a spectral radiometer sensitive to theeffective wavelength of light. Intensive phototherapyrequires a spectral irradiance of 30 W/cm2/nm,delivered over as much of the body surface aspossible.Distance From LightLight intensity is inversely related to the distancebetween the light and the body surface. A simpleTwo halogen spotlight are used to provide morecomplete coverage. Note that the lights are notsuperimposed over the same area of skin but areused to provide coverage over different body surfaceareas on this large infant.www.advancesinneonatalcare.orgCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxp8/24/113:03 AMPage 15Fundamentals of Phototherapy for Neonatal Jaundiceneonatal phototherapy systems achieve vastly different irradiance levels, and this can influence their clinical effectiveness.12Combined phototherapy is often the treatment ofchoice for very preterm infants with hyperbilirubinemia, because it has been shown to achieve lower serumbilirubin levels with a shorter duration of treatment, andto significantly reduce exchange transfusions.15 Onemethod frequently employed to provide combinationphototherapy is to use an overhead unit above the infant(fluorescent bank light, gallium nitride light-emittingdiode [LED], or halogen lamp) and a fiberoptic mattressS15underneath the infant. A commercially available systemcombines banks of fluorescent tubes on each side, witha transparent mattress containing fan-cooled fluorescentbulbs (Bili-Bassinet, Natus Medical Incorporated, SanCarlos, California) (Figure 6).Light-Emitting DiodesThe gallium nitride LED is one of the most recentinnovations in phototherapy (Figure 7). Thesedevices provide high irradiance in the blue to bluegreen spectrum without excessive heat generation.6Light-emitting-diode units are efficient, long-lasting,FIGURE 6.The Bili-Bassinet (Natus Medical Incorporated) is a phototherapy delivery systemthat provides combination phototherapy. Courtesy of Olympic Medical.Advances in Neonatal Care Vol. 11, No. 5SCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxpS168/24/113:03 AMPage 16StokowskiFIGURE 7.Phototherapy system that comprises a light-emitting diode and the option toswitch between single or double phototherapy at the touch of a button (NeoBlue,Natus Medical Inc, San Carlos, California). Courtesy of Natus Medical Inc.and cost-effective.1 The latest models incorporateamber LEDs to counteract the “blue hue” effect thatcan irritate caregivers.1Halogen Spot LightsHalogen lamp sources deliver phototherapy using 1 ormore quartz halogen bulbs (Figure 8). It is possible toachieve sufficient irradiance with halogen light sources;however, devices designed with a single lamp produce acircle of light with high irradiance only in the center.Halogen systems are compact and caregiver-friendly;however, quartz halogen bulbs carry the disadvantage ofgenerating significant amounts of heat. Manufacturer’srecommendations for safe maximal distance should befollowed.11 A newer device that incorporates a metalhalide bulb (Giraffe SPOT PT Lite, GE Healthcare,Waukesha, Wisconsin) is an improvement over earlierhalogen spotlights. The light source is located in a lightbox, away from the infant, resulting in a cooler light surrounding the infant. This high-intensity light is transmitted through a light pipe in a flexible gooseneck that canbe adjusted for maximum light footprint.Fluorescent TubesOften referred to as “bank lights,” fluorescent tubephototherapy devices have been around the longest(Figure 9). It is vital to realize, however, that not allfluorescent tubes are the same. Dramatic differencesexist in the irradiance produced by different types offluorescent tubes, even within the same 425- to 475-nmwavelength.11 Bulbs used in this type of phototherapyunit include daylight, cool-white, blue, “special blue”(the most effective), or a combination of these. Onesystem contains 6 blue tubes and 2 white tubes withan optional on/off switch. Caregivers are often bothered by the blue-hue effect produced by all bluetubes, and the blue light can impair assessment ofinfant skin color. The white light tubes in this unit canbe switched on to minimize the blue-hue effect without hindering the effectiveness of the phototherapytreatment.Fluorescent tube units are often positioned toofar away from the infant to be effective. They shouldbe positioned as close to the infant as possible.8Maisels recommends that these units be placed 10 cmwww.advancesinneonatalcare.orgCopyright 2011 National Association of Neonatal Nurses. Unauthorized reproduction of this article is prohibited.

ANC200224.qxp8/24/113:03 AMPage 17Fundamentals of Phototherapy for Neonatal JaundiceFIGURE 8.S17FIGURE 9.AHalogen spot light phototherapy system. Courtesy ofGE Healthcare. Reprinted with permission.above nude full-term infants in bassinets for effectivephototherapy. This method achieves an irradiance of50 W/cm2 while maintaining normal body temperature8 and has been successfully implemented injaundiced infants 37 or more weeks’ gestation.16Fiberoptic BlanketsFiberoptic devices contain a tungsten-halogen bulbthat delivers light via a cable into a plastic pad containing fiberoptic fibers (Figure 10). The padremains cool and can be placed directly under aninfant to increase the skin surface area that isexposed. The pad can also be wrapped around theinfant’s midsection to provide phototherapy whilethe infant is being held. Because the spectral powerof the pad alone is low, it is commonly used in conjunction with overhead lights to provide doublephototherapy.NURSING CARE OF THE INFANTRECEIVING PHOTOTHERAPYPhototherapy is much more than just switching on alight. The efficiency with which phototherapy achievesa decline in serum bilirubin level is in large part determined by nursing care. Appropriate nursing care alsominimizes the potential side effects and complicationsof phototherapy.BPhototherapy systems that incorporate fluorescenttubes. Conventional bank lights (A) can be positionedover an infant in a bassinet or incubator. Courtesy ofOlympic Medical. An overhead system that combinesblue and white tubes is both

KEY WORDS: bilirubin, hyperbilirubinemia, jaundice, neonatal intensive care, newborn, phototherapy, premature infant P hototherapy is the use of visible light for the treatment of hyperbilirubinemia, or jaundice, in the newborn.1 It is perhaps the most com-mon nonroutine therapy applied in the newborn

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