Neonatal jaundice

Question 1

Go through the normal progression of bilirubin concentrations in a healthy neonate. What percentage of neonates may become jaundiced?

Answer 1

At birth, neonates aren’t jaundiced as placenta has been able to filter bilirubin out. Usually have bilirubin concentration 30-40umol/L (adults have 20umol/L)

Bilirubin quickly increases after birth and peaks around 4 days, before liver enzymes are fully active and bilirubin starts to diminish. May not reach 20umol/L until a few weeks.

50% of neonates may become jaundiced

Question 2

Give 4 reasons why neonates have a greater propensity to become jaundiced than adults

Answer 2

RBCs only have a 60 day half life (= greater haemolysis)
Haem metabolism isn’t as quick (liver enzymes yet to be induced)
Neonates have a greater Hb concentration (which is why they look so red) = more Hb to metabolise

Question 3

What bilirubin concentration is required to see jaundice in a neonate?

Answer 3

> 100umol/L

Question 4

Name 2 reasons why neonatal jaundice may be an important clinical sign

Answer 4

Severe jaundice can cause kernicterus and cerebral damage

Severe jaundice can also reflect an underlying disease in haem metabolism or haemolysis

Question 5

Name 3 instances where you would worry about neonatal jaundice

Answer 5

Early jaundice - less than 24 hours and over 100 umol/L
If conjugated bilirubinaemia is severely high (physiological jaundice usually unconjugated)
If bilirubin stays high for too long (over 100 for over 2 weeks)

Question 6

What values make you worry about early jaundice in a neonate? Give 4 causes of early jaundice

Answer 6

Bilirubin > 100umol/L

Causes:
Red cell isoimmunisation (ABO, Rh, Kell etc)
Alpha thalassaemia
Funny shaped cells (sickle cell, hereditary spherocytosis)
Metabolic (G6PD deficiency)

Question 7

Name 3 blood group incompatibilities that cause severe haemolysis, not mild

Answer 7

D, Kell, c - ABO usually mild (as only a small percentage of antibodies switch to IgG and cross placenta)

Question 8

What test should you do if you suspect a blood group incompatibility causing early haemolysis?

Answer 8

Direct Coombs test to look for presence of autoantibodies

Question 9

Why does alpha but not beta thalassaemia major cause early haemolysis?

Answer 9

Neonatal Hb is in process of switching from A2G2 to A2B2 conformation. Alpha thalassaemia = unstable A2 = will get haemolysis from birth. Beta thalassaemia = unstable B2 = will only get clinically significant haemolysis after transition to adult haemoglobin

Question 10

Name 3 things that can trigger G6PD

Answer 10

Moth balls (napthalene), aspirin, anti-malarial drugs

Question 11

Name 3 causes of severely high conjugated bilirubin in a neonate

Answer 11

Feeding problems (means that less is excreted in bile)
Bowel obstruction (less excreted in bile)
Trauma during birth

Question 12

Name causes of prolonged raised bilirubin in a neonate (3 causes of unconjugated and 3 causes of conjugated bilirubin)

Answer 12

Unconjugated - breastmilk jaundice, congenital hypothyroidism, infection (usually UTI)
Conjugated - biliary atresia, metabolic (galactossaemia), genetic (alpha-1 anti-trypsin deficiency)

Question 13

How can you detect foetal haemolysis in utero? Name 2 management strategies

Answer 13

With MCA Doppler U/S, looking for increased peak systolic velocity (sign of anaemia). If severe, can manage with immediately delivery, or in utero transfusion (via umbilical vein or into peritoneum)

Question 14

What is the usual management of neonatal jaundice? Name 2 SE of the intervention

Answer 14

Phototherapy with visible blue light to photoisomerise the bilirubin. SE - diarrhoea (from excretion of soluble bilirubin), hypothermia (have to remove clothes for treatment)