Neonatal Jaundice

Question 1

Pathophys of neonatal jaundice?

Answer 1

• Yellow discolouration of skin due to raised serum bilirubin.
• Biirubin is a RBC breakdown product.
• Unconjugated bilirubin is produced in the bone marrow, toxic and must be secreted.
• Unconjugated biliribun - lipid soluble and blood insoluble, transported (bound to albumin) to liver to be conjugated, and excrete in urine and faeces.
• Free unconjugated bilirubin can cross blood-brain barrier in neonates (poorly developed barrier) and damage brain cells - Kernicterus.
• Age at onset gives good guide to likely cause of jaundice.

Question 2

Aetiology of neonatal jaundice <24 hours of age?

Answer 2

Always abnormal, usually the result of haemolysis - very serious as bilirubin is unconjugated + rises rapidly - worry about Kernicterus.

1) Rhesus haemolytic disease
2) ABO incompatibility
3) G6PD deficiency
4) Spherocytosis
5) Congenital infection

Question 3

Aetiology of Rhesus haemolytic disease (in <24 hours of age)

Answer 3

• Mother (with rhesus negative blood) creates antibodies against newborns blood (rhesus positive) resulting in haemolysis and jaundice.
• Those with severe rhesus disease have high risk of developing Kernicterus and subsequent brain damage.
• Introduction of the anti-D immunoglobulin against rhesus positive antigens has led to a dramatic reduction in haemolytic anaemia and kernicterus (anti-D neutralises babies blood cell antigens before they can be recognised by mother’s immune system hence no antibodies produced)

Question 4

ABO incompatibility aetiology (<24 hr)?

Answer 4

• Now MORE COMMON that Rhesus disease.
• Mother O - Baby A or B or mother A - baby B (or vice versa)
• Antibodies produced - haemolysis - jaundice (less severe than Rhesus)

Question 5

G6PD deficiency aetiology (<24hr)?

Answer 5

• G6PD is a crucial enzyme essential for normal lifespan of red blood cells, and deficiency = sudden destruction of RBC’s, causing haemolytic anaemia (hence jaundice)

Question 6

Spherocytosis aetiology?
Congenital infection aetiology?
How do these cause jaundice (in children <24 hours old)?

Answer 6

• Spherical RBC’s with reduced life = haemolysis = jaundice.

- Bilirubin conjugated and other signs; growth restriction, hepatosplenomegaly, thrombocytopenia purpura

Question 7

What causes jaundice between 2 days old and 2 weeks old?

Answer 7

• Most often physiological
  1) Physical jaundice of the newborn
  2) Breastmilk jaundice
  3) Infection
  4) Bruising and polycythaemia will exacerbate jaundice
  5) Rare disease - Criglet-Najjar syndrome (glucoronyl transferase deficiency - high levels of unconjugated bilirubin)

Question 8

Physiological jaundice of the newborn aetiology? (2days-2weeks)

Answer 8

• Increased RBC turnover as foetal haemoglobin has a shorter lifespan - 70 days.
• As baby transitions from foetal life - destroys more foetal haemoglobin = more haemolysis and jaundice.
• Decreased bilirubin conjugation due to hepatic immaturity.

Question 9

Breast milk jaundice aetiology? (2days-2weeks)

Answer 9

• Jaundice is more common and more prolonged in breastfed infants - believed to be due to a substance in breast milk that prevents bilirubin breakdown
• Results in unconjugated jaundice

Question 10

Infection causing jaundice aetiology? (2days-2weeks)

Answer 10

• Infected baby may develop unconjugated hyperbilirubinaemia from poor fluid intake, haemolysis, hepatic function and increase in the enterohepatic circulation.

Question 11

Jaundice at >2 weeks - persistent neonatal jaundice?

Answer 11

Unconjugated:

• Breast milk jaundice - most common cause, gradually disappears by 4-5 weeks of age.
• Infection - particularly of the urinary tract.
• Congenital hypothyroidism.- identified on Guthrie test.

Conjugated (dark urine+pale stools):

• Neonatal hepatitis syndrome
• Biliary atresia

Question 12

Severity of jaundice and rate of change?

Answer 12

• Blanch skin with finger
• Jaundice starts on the head and face and spreads down.
• Linear rate of rise until it reaches plateau - enables serial measurements to be plotted to anticipate need for treatment.

Question 13

Which children are susceptible to jaundice?

Answer 13

• Preterm infants most susceptible - intervention threshold is lower.
• Infants experiencing hypoxia, hypothermia, or any serious illness.
• Drugs that displace bilirubin from albumin (e.g. diazepam) are avoided in newborn infants

Question 14

Management of neonatal jaundice?

Answer 14

1) Phototherapy - Light from the blue-green band of the visible spectrum can convert unconjugated bilirubin into a harmless water-soluble pigment which is excreted in urine.
- Infant’s eyes should be covered for protection.
- Continuous phototherapy given if bilirubin is rising rapidly or is very high.

2) Exchange transfusion -
- Required if bilirubin levels have risen to dangerous levels.
- Blood is removed from the baby and replaced with donor blood.
- Twice the infant’s blood volume is exchanged
- Aim is to remove bilirubin as fast as possible.