Transcutaneous Bilirubin

Monitoring

12

Aimee M. Barton

Melissa Scala

A. Background

1. Jaundice occurs in most newborn infants. A high level

of unconjugated bilirubin is potentially toxic to the nervous system, causing bilirubin encephalopathy and kernicterus (1).

2. 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) (2,3).

3. Visual assessment of jaundice, although clinically

important, may not be accurate (4,5).

4. Transcutaneous bilirubinometers measure the yellowness of reflected light from the skin and subcutaneous

tissues to provide an objective noninvasive measurement of the degree of neonatal jaundice and thereby

predict the approximate TSB.

5. Transcutaneous bilirubinometers are predominantly

used for screening for significant hyperbilirubinemia in

term and near-term newborn infants.

6. Two transcutaneous bilirubinometers are currently

used in the United States. Although these instruments use different technologies and algorithms,

their underlying principles of operation are similar.

Both bilirubinometers provide TCB measurements

that correlate well with TSB values at levels <15 mg/

dL, in term and late preterm newborn infants; but

wider variations have been noted at higher bilirubin

levels (6,7).

a. Konica Minolta/Air-Shields JM-103 Jaundice Meter

(Dräger Medical, Telford, Pennsylvania) (5,8) (Fig.

12.1)

b. BiliChek Noninvasive Bilirubin Analyzer

(Children’s Medical Ventures/Respironics, Norwell,

Massachusetts) (5,7) (Fig. 12.2).

c. Two other transcutaneous bilirubinometers, the

Bilitest BB77 (Bertochhi SRL Elettromedicali,

Cremona, Italy) and BiliMed (Medick SA, Paris,

France) are used in Europe, but are not approved

for use in the United States (9,10).

B. Indications

1. TCB may be obtained

a. 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 (Figs. 12.3 and 12.4) (2,3,11). The

American Academy of Pediatrics recommends routine predischarge bilirubin screening of all newborns.

b. For repeated noninvasive measurement of progression

of jaundice in term or near-term newborn infants.

c. When clinical jaundice is noted in the first 24 hours

of life

d. When jaundice appears excessive for the infant’s age

2. TSB (in addition to other studies to determine underlying pathology) should be obtained when (2,3)

a. Infant is receiving phototherapy or the TSB is rising

rapidly

b. TSB value approaching exchange transfusion levels

or not responding to phototherapy

c. Infant has an elevated direct bilirubin level

d. Jaundice is present at or beyond age 3 weeks

e. In sick or premature (<35 weeks’gestation) infants

C. Limitations

1. TCB measurement is a screening tool and should not

be used for treatment decisions, but rather to select

those infants who should undergo TSB measurement (1).

2. 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).

3. All TCB devices are not the same. Significant variations can occur among instruments (9). New instruments should be compared with hospital laboratory

measurements.

4. TCB measurements become less accurate if the infant

is being treated with phototherapy or has received an

80 Section II ■ Physiologic Monitoring

Fig. 12.1. Use of the Konica Minolta/Air-Shields JM-103 Jaundice

Meter on the sternum. (Photo provided by Dräger Medical.)

Fig. 12.2. Use of the BiliChek Noninvasive Bilirubin Analyzer

on the forehead. (Photo provided by Children’s Medical Ventures/

Respironics.)

Fig. 12.3. 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.)

exchange transfusion and should not be used within

24 hours of either of these therapies (2,5,12–14).

a. 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 (13,14). Correlation

coefficients have been found to decrease to as low as

0.33 in infants undergoing phototherapy for longer

than 48 hours (13).