Atlas of Procedures in Neonatology, 4th Edition

Physiologic Monitoring

11

Transcutaneous Bilirubin Testing

Aimee M. Barton

  1. Background
  2. Jaundice occurs in most newborn infants. Bilirubin at high levels is potentially toxic to the nervous system, causing bilirubin encephalopathy and kernicterus (1).
  3. A systematic assessment of all newborn infants for the risk of severe hyperbilirubinemia should be undertaken prior to discharge, and appropriate follow-up should be provided. This assessment may be performed by measuring total serum bilirubin (TSB) or transcutaneous bilirubin (TCB) (2).
  4. Visual assessment of jaundice, although clinically important, may not be accurate (3, 4).
  5. Transcutaneous bilirubinometers measure the yellowness of reflected light from the skin and subcutaneous tissues to provide an objective noninvasivemeasurement of the degree of neonatal jaundice and thereby predict the approximate TSB.
  6. Transcutaneous bilirubinometers are used predominantly for screeningfor significant hyperbilirubinemia in term and near-term newborn infants.
  7. Two transcutaneous bilirubinometers are currently in use in the United States. Although these instruments use different technologies and algorithms, their underlying principles of operation are similar.
  8. Konica Minolta/Air-Shields JM-103 Jaundice Meter (Dräger Medical, Telford, PA, USA) (4, 5) (Fig. 11.1)
  9. BiliChek Noninvasive Bilirubin Analyzer (Children's Medical Ventures/Respironics, Norwell, MA, USA) (4, 6) (Fig. 11.2)
  10. Both bilirubinometers have been found to provide TCB measurements that correlate well with TSB values at levels <15 mg/dL, in term and near-term newborn infants, but wider variations have been noted at higher bilirubin levels (6, 7).
  11. Indications
  12. TCB may be obtained:
  13. As part of routine predischarge assessment between 1 and 4 days of life in term and near-term newborn infants, to assess the risk of development of severe hyperbilirubinemia, by using the hour-specific bilirubin nomogram (2, 8). (Fig. 11.3)
  14. For repeated noninvasive measurement of progression of jaundice in term or near-term newborn infants.
  15. When clinical jaundice is noted in the first 24 hours of life
  16. When jaundice appears excessive for the infant's age
  17. TSB (in addition to other studies to determine underlying pathology) should be obtained when (2):
  18. Infant is receiving phototherapy or the TSB is rising rapidly
  19. TSB concentration approaching exchange transfusion levels or not responding to phototherapy
  20. Infant has an elevated direct bilirubin level
  21. Jaundice is present at or beyond age 3 weeks
  22. In sick or premature (<35 weeks' gestation) infants
  23. Limitations
  24. TCB measurement is a screening tooland should not be used for treatment decisions, but rather to select those infants who should undergo TSB measurement (1).
  25. The two large studies evaluating the BiliChek device and the JM-103 device included few patients with TSB values >15 mg/dL. The accuracy of TCB measurement in this range has not been evaluated adequately (6, 7).
  26. TCB measurements become less accurate if the infant is being treated with phototherapy or has received an exchange transfusion and should not be used within 24 hours of either of these therapies (2, 4, 9, 10).
  27. Phototherapy alters the chemical structure of bilirubin in the subcutaneous tissues, making it more water-soluble. Measurement of TCB in infants undergoing phototherapy is not reliable because the large decrease in subcutaneous bilirubin may not yet be reflected in the serum (9, 10).

P.74

  1. One study found that correlation coefficients decreased from 0.90 before phototherapy to 0.85 upon initiation of phototherapy. This trend continued with prolonged phototherapy, with correlation coefficients as low as 0.33 in infants undergoing phototherapy for longer than 48 hours (9).
  2. TCB measurements are less accurate in preterm infants.
  3. When compared with TSB measurement, the BiliChek System has been shown to have a correlation coefficient of 0.86 in preterm infants who are not receiving phototherapy (10).
 

FIG. 11.1. Use of the Konica Minolta/Air-Shields JM-103 Jaundice Meter on the sternum. (Photo provided by Dräger Medical.)

 

FIG. 11.2. Use of the BiliChek Noninvasive Bilirubin Analyzer on the forehead. (Photo provided by Children's Medical Ventures/Respironics.)

P.75

 

 

FIG. 11.3. Nomogram for designation of risk in 2,840 well newborns at 36 or more weeks' gestational age with birth weight of 2,000 g or more or 35 or more weeks' gestational age and birth weight of 2,500 g or more based on hour-specific serum bilirubin values (2, 8). (Reproduced with permission from Pediatrics, Vol. 114, Page 301, Copyright © 2004 by the AAP.)

  1. Equipment
  2. Two TCB monitors are currently in use in the United States
  3. Konica Minolta/Air-Shields JM-103 Jaundice Meter (Dräger Medical, Telford, PA, USA) (Figs. 11.1 and 11.4)
  4. Determines the yellowness of subcutaneous tissue by measuring the difference between optical densities for light in the blue and green wavelengths
  5. Measurement probe has two optical paths
  6. By calculating the difference between the optical densities, the parts common to the epidermis and dermis are deducted. As a result, the difference can be obtained for subcutaneous tissue only.
  7. Theoretically allows for measurement of degree of yellowness of skin and subcutaneous tissue with minimal influence of melanin pigment and skin maturity
  8. Linear correlation of this measurement with TSB allows for conversion to TSB by the meter, which is indicated digitally.
  9. BiliChek Noninvasive Bilirubin Analyzer (Children's Medical Ventures/Respironics, Norwell, MA, USA) (Figs. 11.2 and 11.5)
  10. Noninvasive device consisting of light source, microspectrophotometer, fiber-optic probe, and microprocessor control circuit
  11. Uses entire spectrum of visible light reflected by the skin
  12. White light is transmitted into the skin and the reflected light is collected for analysis.
  13. Algorithms take into account the effect of hemoglobin, melanin, and dermal thickness.
  14. Absorption of light due to bilirubin in the capillary bed and subcutaneous tissue is isolated by spectral subtraction.
  15. Special Circumstances/Considerations
  16. Hospital protocols should include the conditions under which TCB and TSB levels are to be obtained (1).
  17. Only TSB measurements should be performed in infants with severe enough jaundice to warrant exchange transfusion (6).
  18. TCB is less accurate in infants undergoing phototherapy and therefore serum levels are preferred for monitoring bilirubin values in such infants (2, 4, 8, 9).

P.76

 

  1. Race/skin color: TCB readings obtained by the BiliChek have been found to correlate with TSB values in white, black, Asian, Hispanic, indigenous African, and Indian infants (6, 9, 11). In black infants, TCB readings obtained by the JM-103 correlate less closely with TSB values, with the TCB generally being greater than the TSB (7).
 

FIG. 11.4. Measurement principle of Konica Minolta/Air-Shields JM-103 Jaundice Meter. (Reproduced with permission from 

J Perinat Med., Vol. 31, Pages 81–88, Copyright © 2003 by Walter de Gruyter GmbH & Co. KG Berlin, New York

.)

  1. Techniques
  2. Calibrate the TCB device according to manufacturer specifications.
  3. Measure TCB by pressing the trigger button and gently pressing the tip to the infant's forehead or sternum until the device indicates that reading is complete.
  4. Some studies have shown that TCB measurements from the sternum correlated slightly better with TSB levels than TCB measurements from the forehead, possibly as a result of the exposure of the forehead to ambient light. Other studies indicate both sites to be equivalent (7, 12).
  5. Measurements must be taken in a consistent manner with regard to placement of the probe and amount of pressure applied to the device. Interoperative and intraoperative variability may be minimized with proper training (7).
  6. Measurement of the TCB using the BiliChek system takes approximately 20 to 80 seconds. This time is required for the monitor to make five measurements that are averaged to provide one TCB value. The JM-103 takes approximately 10 seconds to obtain its dual measurements and calculate the TCB value.
  7. Repeated use of the disposable probes is not recommended.
 

FIG. 11.5. Measurement principle of the BiliChek Noninvasive Bilirubin Analyzer. (Reproduced with permission of Children's Medical Ventures/Respironics.)

  1. Complications
  2. No complications have been reported from the use of TCB monitors, apart from the risk of inappropriate use and the possibility of underestimation of the level of jaundice.

P.77

 

References

  1. American Academy of Pediatrics Subcommittee on Hyperbilirubinemia.Neonatal jaundice and kernicterus. Pediatrics. 2001;108(3):31–39.
  2. American Academy of Pediatrics Subcommittee on Hyperbilirubinemia.Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics. 2004;114:297–316.
  3. Szabo P, Wolf M, Bucher HU, et al. Detection of hyperbilirubinaemia in jaundiced full-term neonates by eye or bilirubinometer? Eur J Pediatr. 2004;163(12):722–727.
  4. Maisels MJ.Transcutaneous bilirubinometry. NeoReviews. 2006;7(5):e217–e225.
  5. Yasuda S, Itoh S, Isobe K, et al. New transcutaneous jaundice device with two optical paths. J Perinat Med. 2003;31:81–88.
  6. Bhutani VK, Gourley GR, Adler S, et al. Noninvasive measurement of total serum bilirubin in a multiracial predischarge newborn population to assess the risk of severe hyperbilirubinemia. Pediatrics. 2000;106:e17.
  7. Maisels MJ, Ostrea EM, Touch S, et al. Evaluation of a new transcutaneous bilirubinometer. Pediatrics. 2004;113:1628–1635.
  8. Bhutani VK, Johnson L, Sivieri EM.Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns. Pediatrics. 1999;103(1):6–14.
  9. Mahajan G, Kaushal RK, Sankhyan N, et al. Trancutaneous bilirubinometer in assessment of neonatal jaundice in Northern India.Indian Pediatr. 2005;42:41–45.
  10. Nanjundaswamy S, Petrova A, Mehta R, Hegyi T.Transcutaneous bilirubinometry in preterm infants receiving phototherapy. Am J Perinatol. 2005;22(3):127–131.
  11. Slusher TM, Angyo IA, Bode-Thomas F, et al. Transcutaneous bilirubin measurements and serum total bilirubin levels in Indigenous African infants. Pediatrics. 2004;113:1636–1641.
  12. Ebbesen F, Rasmussen LM, Wimberley PD.A new transcutaneous bilirubinometer, BiliChek®, used in the neonatal intensive care unit and the maternity ward. Acta Paediatr. 2002; 91:203–211.