Page 61 - 16Neonatal Jaundice_compressed

Neonatal jaundice

completely understood and the condition appears to be generally harmless. However, prolonged
jaundice can be a clue to serious underlying liver disease and should be assessed carefully.

Causes of pathological jaundice
Jaundice may also have other, non-physiological, causes, including blood group incompatibility
(most commonly Rhesus or ABO incompatibility), other causes of haemolysis, sepsis, bruising
and metabolic disorders. Gilbert syndrome and Crigler–Najjar syndrome are rare causes of
neonatal jaundice and are caused by liver enzyme problems. Deficiency of a particular enzyme,
glucose-6-phosphate dehydrogenase (G6PD), can cause severe neonatal jaundice. G6PD
deficiency is more common in certain ethnic groups and is familial. Congenital obstruction and
malformations of the biliary system, such as biliary atresia, cause an obstructive jaundice with
conjugated hyperbilirubinaemia. This condition needs specialist investigation and early surgical
treatment, preferably before 8 weeks of life.

Bilirubin encephalopathy and kernicterus
In young babies, unconjugated bilirubin can penetrate the membrane that lies between the
brain and the blood (the blood–brain barrier). Unconjugated bilirubin is potentially toxic to
neural tissue (brain and spinal cord). Entry of unconjugated bilirubin into the brain can cause
both short-term and long-term neurological dysfunction. Acute features include lethargy,
irritability, abnormal muscle tone and posture, temporary cessation of breathing (apnoea) and
convulsions. This presentation is known as acute bilirubin encephalopathy. Bilirubin is
deposited particularly in a part of the brain known as the globus pallidus, part of the ‘deep grey
matter’ of the brain. On pathological examination of the brain, this produces yellow staining;
this staining is referred to as kernicterus. The term kernicterus is also used to denote the clinical
features of acute or chronic bilirubin encephalopathy. Features of the latter include athetoid
cerebral palsy, hearing loss, and visual and dental problems. The exact level of bilirubin that is
likely to cause neurotoxicity in any individual baby varies, and depends on the interplay of
multiple factors which include acidosis, gestational and postnatal age, rate of rise of serum
bilirubin, serum albumin concentration, and concurrent illness (including infection).
Although neonatal jaundice is very common, kernicterus is very rare. There is a poor correlation
between levels of circulating bilirubin and the occurrence of bilirubin encephalopathy. There
seems to be tremendous variability in susceptibility towards bilirubin encephalopathy among
newborns for a variety of unexplained reasons. However, there are certain factors that probably
influence the passage of bilirubin into the brain and hence increase the risk of acute bilirubin
encephalopathy. These include preterm birth, sepsis, hypoxia, seizures, acidosis and
hypoalbuminaemia. The rate of rise of the level of bilirubin is probably important, hence the
increased risk of kernicterus in babies with haemolytic disease such as G6PD deficiency, ABO
or Rhesus haemolytic disease.
Kernicterus in healthy term babies with none of the above factors is virtually unknown below a
serum bilirubin concentration of 450 micromoles of bilirubin per litre (micromol/litre), but the
incidence increases above this threshold level and the risk of kernicterus is greatly increased in term
babies with bilirubin levels above 515 micromol/litre. Kernicterus is also known to occur at lower
levels of bilirubin in preterm and in term babies who have any of the factors described above.

Treatment of jaundice
Levels of bilirubin can be controlled by placing the baby under a lamp emitting light in the blue
spectrum, which is known as phototherapy. Light energy of the appropriate wavelength converts the
bilirubin in the skin to a harmless form that can be excreted in the urine. Phototherapy has proved to
be a safe and effective treatment for jaundice in newborn babies, reducing the need to perform an
exchange transfusion of blood (the only other means of removing bilirubin from the body).
Clinical recognition and assessment of jaundice can be difficult. This is particularly so in babies
with darker skin. Once jaundice is recognised, there is uncertainty about when to treat. Currently,
there is widespread variation in the use of phototherapy, exchange transfusion and other
treatments when using charts, but there is already a degree of consistency in the NHS about
treatment thresholds when healthcare professionals base their decisions on a formula that uses

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