Jaundice Flashcards
Why do neonates become jaundiced? What is the physiology?
Physiological jaundice
- Relatively high concentration of haemoglobin at birth, reduces over subsequent days
- Shorter lifespan of haemoglobin in neonates
- Therefore, increased red cell breakdown, meaning increased production of bilirubin
- Immature hepatic enzymes impairs bilirubin conjugation and excretion
- Increased reabsorption of bilirubin via enterohepatic circulation
Beware possible pathological causes of jaundice.
Describe bilirubin metabolism.
Bilirubin is product of haemoglobin breakdown.
Unconjugated bilirubin travels in blood as free unconjugated bilirubin, or bound to albumin.
In the liver it is conjugated with glucuronic acid by glucuronyl transferase. This makes it water soluble. It is secreted into gut via common bile duct.
In the gut it is metabolised to urobilinogen and some is reabsorbed via enterohepatic circulation. Urobilinogen is metabolised to stercobilin (excreted in faeces), and some is reabsorbed and excreted in urine as urobilinogen.
What is kernicterus? How does it present?
Kernicterus is a type of encephalopathy caused by a toxic build up of unconjugated bilirubin in the basal ganglia and brainstem nuclei. Free unconjugated bilirubin is able to cross the blood brain barrier.
presentation:
- irritability
- drowsiness
- poor feeding
- opisthonus
- seizures
- death
What are the possible causes of jaundice within the first 24 hours?
Always pathological:
- haemolytic disease of newborn (HDFN) due to Rhesus disease, anti-c, anti-K
- ABO or minor blood antigen incompatibility
- Sepsis
- G6PD deficiency
- Hereditary spherocytosis
- congenital infections (CMV, toxo, rubella and syphilis - cause hepatitis and conjugated hyperbilirubinemia)
- Hepatitis
NB If conjugated bilirubin >15% total bilirubin, likely hepatitis
What are the possible causes of jaundice after 24hours, in the first 2 weeks?
- Physiological
- Breast milk jaundice / dehydration
- Haemolytic causes
- Infections
- Bruising / birth trauma
- GI obstruction
- Metabolic disorders
- Liver enzyme defect (crigler-najjer syndrome - autosomal recessive, absence of enzyme needed for glucuronidation)
What are the possible causes of jaundice after 2 weeks?
Unconjugated:
- Dehydration
- breast milk jaundice
- hypothyroidism
- Infection (most commonly UTI)
Conjugated:
- Neonatal hepatitis (commonly viral)
- Biliary atresia
Investigations for jaundice?
- Careful regular physical examination for signs of jaundice within first 72 hours and at each visit
- Transcutaneous bilirubinography screening (if available)
- Serum total bilirubin (usually from heal prick)
- Conjugated bilirubin
- FBC, G&H
- DAT
- Elution testing for anti-A and anti-B Abs (more sensitive than direct combes)
- Consider blood film for haemolysis
- CRP (and septic screen if indicated)
- Maternal blood group and Abs titres - if not already known
If > 2weeks postpartum, consider adding:
- Check neonatal screening completed for hypothyroidism
- urine MC&S
Management of jaundice?
- Plot total serum bilirubin on a gestation specific chart to work out if baby meets threshold for phototherapy, or exchange transfusion
- Manage underlying cause of jaundice (i.e. treat infection etc)
- Ensure adequate hydration to minimise reabsorption via enterohepatic circulation (i.e. increase breast feeding to 8-12 x daily or top-up feed expressed/formula milk)
- Phototherapy
- exchange transfusion (for severe hyperbilirubinemia, anaemia and to remove antibodies from blood - most likely required for HDFN)
- IV immunoglobulin for haemolytic disease persisting despite exchange transfusion
What re the main risk factors for severe hyperbilirubinemia?
- jaundice within the first 24 hours
- blood group incompatibility; particularly Rhesus (Rh) incompatability
- previous sibling requiring phototherapy for haemolytic disease
- cephalhaematoma or significant bruising
- weight loss greater than 10 per cent of birthweight; may be associated with ineffective breastfeeding
- family history of red cell enzyme defects (such as G6PD deficiency) or red cell membrane defects (such as hereditary spherocytosis).
Why can breast milk cause jaundice?
- Not fully understood
- Breast milk high in unsaturated fatty acids and lipase, which may inhibit glucuronyl transferase action
What are the complications of phototherapy?
overheating water loss diarrhoea ileus (preterm infants) rash (no specific treatment required) retinal damage (theoretical) parental anxiety/separation 'bronzing' of infants with conjugated hyperbilirubinemia.
