Phototherapy
Suhasini Kaushal
Jayashree Ramasethu
Phototherapy is the most common therapeutic intervention used for the treatment of unconjugated hyperbilirubinemia in neonates. The aim of phototherapy is to reduce serum bilirubin levels to decrease the risk of acute bilirubin encephalopathy and the chronic sequel of bilirubin toxicity, kernicterus (1).
Phototherapy causes isomerization of the bilirubin molecule (bilirubin IX-α, Z,Z configuration) to polar, water-soluble photoproducts (conformational photoisomers Z,E and E,Z bilirubin, and structural photoisomers E,Z and E,E lumibilirubin). These photoisomers can be excreted in bile and urine without the need for conjugation or further metabolism (2, 3). Photo-oxidation plays a smaller role in the excretion of bilirubin.
A. Indications
1. Clinically significant hyperbilirubinemia. Indications to start phototherapy in babies with unconjugated hyperbilirubinemia vary depending on gestational age, birth-weight, age in hours, presence of hemolysis, and other risk factors such as acidosis and sepsis (1, 4).
2. The total serum bilirubin (TSB) level must be considered when making the decision to commence treatment, as there is significant variability in laboratory measurement of direct bilirubin levels (1).
3. The American Academy of Pediatrics has published clinical practice guidelines for phototherapy in newborn infants at 35 weeks’ or more gestation (Fig. 55.1) (1).
 FIGURE 55.1 Guidelines for phototherapy in hospitalized infants of 35 or more weeks’ gestation. (Reprinted with permission from American Academy of Pediatrics Subcommittee on Hyperbilirubinemia. Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics. 2004;114(1):297-316. Erratum: Pediatrics. 2004;114(4):1138. Copyright © 2004 by the AAP.) |
4. Guidelines for phototherapy for preterm infants <35 weeks’ gestation have been proposed, but are much more variable and highly individualized (see Table 49.1 (5, 6, 7).
5. In extremely low-birth-weight (ELBW) infants, aggressive early phototherapy reduces peak bilirubin levels and rates of neurodevelopmental disability, but has been associated with higher mortality (8).
B. Contraindications
1. Congenital porphyria or a family history of porphyria is an absolute contraindication to the use of phototherapy. Severe purpuric bullous eruptions have been described in neonates with congenital erythropoietic porphyria treated with phototherapy (9).
2. Concomitant use of drugs or agents that are photosensitizers (10).
3. Concurrent therapy with metalloporphyrin heme oxygenase inhibitors has been reported to result in mild transient erythema (11).
4. Although infants with cholestatic jaundice may develop the “bronze baby syndrome” when exposed to phototherapy (see H), the presence of direct hyperbilirubinemia is not considered to be a contraindication (1). However, because the products of phototherapy are excreted in the bile, the presence of cholestasis may decrease the effectiveness of phototherapy.
C. Equipment
Terminology
It is important to be familiar with specific terminology to understand the functioning of the equipment available for phototherapy (2, 12).
1. Spectral qualities of the delivered light (wavelength range and peak). Bilirubin absorbs visible light within the wavelength range of 400 to 500 nm, with peak absorption at 460 to 490 nm considered to be the most effective (2, 3, 13). Note: Phototherapy is not ultraviolet (UV) light (wavelength 10 to 400 nm).
2. Irradiance (intensity of light), expressed as watts per square centimeter (W/cm2), refers to the number of photons received per square centimeter of exposed body surface area.
3. Spectral irradiance is irradiance that is quantitated within the effective wavelength range for efficacy and is expressed as µW/cm2/nm. This is measured by various commercially available radiometers. Specific radiometers are generally recommended for each phototherapy system, because measurements of irradiance may vary depending on the radiometer and the light source (1, 2, 12).
Devices
Phototherapy equipment may be freestanding, attached to a radiant warmer, wall-mounted, suspended from the ceiling, or fiberoptic systems. These in turn may contain various light sources to deliver the phototherapy. The clinician is, therefore, faced with a vast array of equipment to choose from and must be aware of advantages and disadvantages of each type.
1. Gallium nitride light-emitting diodes (LEDs)
a. These systems are semiconductor phototherapy devices capable of delivering high spectral irradiance levels of >200 µW/cm2/nm with very little generation of heat within a very narrow emission spectrum in the blue range (460 to 485 nm), with low infrared emission and no UV emission (2, 12, 13).
b. LEDs have a longer lifetime (>20,000 hours) and have become cost effective for use in phototherapy devices.
2. Fluorescent tubes
a. “Special blue” tubes, such as F20T12/BB, provide more irradiance in the blue spectrum than other tubes and are the most effective fluorescent light source (2). “Special blue F20T12/BB” tubes provide much greater irradiance than regular blue tubes, labeled F20T12/B. The flickering glare of the blue light has been reported to cause giddiness, nausea, and temporary blurring of vision in nursing personnel (12). One way to overcome this has been to use cool white light in conjunction with the special blue, but this combination can decrease efficacy by as much as 50%, depending on the proportion of cool white light used (14).
b. Daylight lamps, like cool white lamps, have a wider wavelength spectrum and are less effective than blue light (15).
c. Turquoise (peak irradiance 490 nm) and blue-green lights have also been used for phototherapy (16, 17).
3. Fiberoptic systems
a. UV-filtered light from a tungsten-halogen bulb enters a fiberoptic cable and is emitted from the sides and end of fiberoptic fibers inside a plastic pad.
b. The pad emits insignificant levels of heat, so it can be placed in direct contact with the infant to deliver up to 35 µW/cm2/nm of spectral irradiance, mainly in the blue-green range (18).
c. The orientation of the fiberoptic fibers determines the uniformity of emission and is unique to each of the commercially available devices.
d. The main advantage of these systems is that, while receiving phototherapy, the infant can be held and/or nursed, thereby minimizing infant-parent separation. In addition, covering the infant’s eyes is not necessary, decreasing parental anxiety.
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