Neonatal Jaundice - Associates in Newborn Medicine

neonatology
neonatal jaundice
Table 8. Laboratory Tests for the Jaundiced Infant
When there is a finding of:
Jaundice in first 24 h
Jaundice that appears excessive for the infant’s age
An infant receiving phototherapy or having a TSB that is
above the 75th percentile or rising rapidly (ie, crossing
percentiles) and unexplained by history or findings on
physical examination
A TSB approaching exchange level or not responding to
phototherapy
An elevated direct (or conjugated) bilirubin level
Jaundice present at or beyond age 3 wk or the infant
is sick
Obtain:
Total serum bilirubin (TSB)
TSB
Blood type; also, perform a Coombs test, if not obtained with
cord blood
Complete blood count, smear, and reticulocyte count
Direct (or conjugated) bilirubin
(Repeat TSB in 4 to 24 hours, depending on infant’s age and
TSB level)
Consider the possibility of glucose-6-phosphate
dehydrogenase (G-6PD) deficiency, particularly in African-
American infants
Reticulocyte count, G-6PD test, albumin
Urinalysis and urine culture; evaluate for sepsis if indicated
by history and physical examination
Total and direct bilirubin concentration; if direct bilirubin is
elevated, evaluate for causes of cholestasis
(Also check results of newborn thyroid and galactosemia
screen and evaluate infant for signs or symptoms of
hypothyroidism)
Reprinted with permission from Maisels MJ. Jaundice in a newborn. How to head off an urgent situation. Contemp Pediatr. 2005;22:41–54. Adapted with
permission from Pediatrics. 2004;14:297–316.
other risk factors) always should be one above which a
TSB value always will be obtained. In our nursery, we
routinely evaluate infants via a TcB measurement and
obtain a TSB whenever the TcB is above the 75th percentile
(Fig. 2) (or the 95th percentile in Fig. 1-E).
Treatment
Hyperbilirubinemia can be treated via: 1) exchange
transfusion to remove bilirubin mechanically; 2) phototherapy
to convert bilirubin to products that can bypass
the liver’s conjugating system and be excreted in the bile
or in the urine without further metabolism; and 3) pharmacologic
agents to interfere with heme degradation and
bilirubin production, accelerate the normal metabolic
pathways for bilirubin appearance, or inhibit the enterohepatic
circulation of bilirubin. Guidelines for the use of
phototherapy and exchange transfusion in term and
near-term infants are provided in Figs. 3 and 4 and Table
9.
Phototherapy
Phototherapy works by infusing discrete photons of energy
similar to the molecules of a drug. These photons
are absorbed by bilirubin molecules in the skin and
subcutaneous tissue, just as drug molecules bind to a
receptor. The bilirubin then undergoes photochemical
reactions to form excretable isomers and breakdown
products that can bypass the liver’s conjugating system
and be excreted without further metabolism. Some
photo products also are excreted in the urine.
Phototherapy displays a clear dose-response effect,
and a number of variables influence how light works to
lower the TSB level. (In the online edition of this article,
Table 1-E shows the radiometric units used to measure
the dose of phototherapy and Tables 2-E and 3-E show
the factors that affect the dose and efficacy of phototherapy,
including type of light source, the infant’s distance
from the light, and the surface area exposed.) Because of
the optical properties of bilirubin and skin, the most
effective lights are those that have wavelengths predominately
in the blue-green spectrum (425 to 490 nm). At
these wavelengths, light penetrates the skin well and is
absorbed maximally by bilirubin.
Using Phototherapy Effectively
Phototherapy was used initially in low-birthweight and
term infants primarily to prevent slowly rising bilirubin
concentrations from reaching levels that might require
exchange transfusion. Today, phototherapy often is used
in term and near-term infants who have left the hospital
and are readmitted on days 4 to 7 for treatment of TSB
concentrations of 20 mg/dL (342 mcmol/L) or more.
Such infants require a full therapeutic dose of phototherapy
(now termed intensive phototherapy) to reduce the
450 Pediatrics in Review Vol.27 No.12 December 2006
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