Makindo Medical Notes

🧾 About

• Kernicterus = bilirubin-induced neurological dysfunction due to severe unconjugated hyperbilirubinaemia.
• Occurs when TSB > 360 μmol/L in most term infants (lower thresholds in preterm/ill neonates).
• 50–60% of term newborns develop some jaundice in the first week; usually benign, but a minority progress to kernicterus if untreated.
• Peak bilirubin: day 3–5 in term infants (later in Asian neonates).

⚙️ Aetiology & Pathophysiology

• Unconjugated bilirubin crosses the immature blood–brain barrier if albumin binding is exceeded.
• Albumin normally buffers bilirubin (neuroprotection).
• Excess free bilirubin → deposits in basal ganglia (esp. globus pallidus) → neuronal necrosis/apoptosis.

🩺 Clinical Features

• Early: poor feeding, lethargy, hypotonia.
• Progression: irritability, hypertonia, opisthotonus (arching), high-pitched cry.
• Auditory damage: sensorineural hearing loss (due to cochlear nuclei involvement).
• Severe: seizures, encephalopathy, coma → death if untreated.

⚠️ Risk Factors for Neurotoxicity

• Bilirubin > albumin binding capacity.
• Albumin displacement by drugs (e.g. sulfonamides, ceftriaxone) or acidosis.
• Prematurity (immature BBB + low albumin).
• Sepsis, hypoxia, metabolic derangements.

🔍 Differentials

• Sepsis/Meningitis: lethargy, encephalopathy, poor feeding.
• Hypoxic-Ischaemic Encephalopathy (HIE): abnormal tone, seizures.
• Metabolic disorders: galactosaemia, hypothyroidism.
• Intracranial haemorrhage.
• TORCH infections: congenital causes of jaundice + neuro signs.

🧪 Investigations

• Bloods: FBC, U&E, LFTs, Coombs test, sepsis screen.
• Bilirubin levels:
  • < 323 μmol/L: usually safe in term infants.
  • > 360 μmol/L: requires urgent intervention (thresholds lower in preterm).
• MRI: Kernicterus shows T2 hyperintensity in globus pallidus.

💊 Management

• Emergency: Neonatal jaundice + encephalopathy = treat immediately.
• Phototherapy: Blue light converts unconjugated bilirubin to soluble isomers excreted without conjugation. Increase intensity if rising fast.
• Exchange transfusion: If phototherapy fails or bilirubin dangerously high. Involves replacing blood in aliquots with donor blood.
• Supportive: optimise hydration, correct acidosis, treat sepsis.

💡 Teaching Pearls

• OSCE buzzword: sleepy jaundiced baby with opisthotonus → think kernicterus.
• Preterm babies are at risk at lower bilirubin levels.
• Ceftriaxone is contraindicated in neonates due to bilirubin displacement.
• Phototherapy works by photoisomerisation of bilirubin, not by liver metabolism.

📚 References

• NICE NG98: Neonatal jaundice (2016).
• Rennie & Roberton’s Textbook of Neonatology, 5th Ed.
• Maisels MJ. Kernicterus and bilirubin encephalopathy. N Engl J Med. 2006.