Jaundice treatment and congenital screening

Phototherapy, Exchange Transfusion & Kernicterus

Mechanism & Principles of Phototherapy

Phototherapy utilizes blue-green light in the 460 to 490 nm wavelength spectrum. Light penetrates neonatal skin and converts lipid-soluble unconjugated bilirubin ($4Z,15Z$-bilirubin) into two water-soluble isomers via non-enzymatic photochemical reactions:

1. Structural photoisomerization: Produces lumirubin, an irreversible structural isomer that is rapidly cleared in bile and urine without requiring glucuronic acid conjugation (the primary pathway of bilirubin excretion under phototherapy).
2. Configurational photoisomerization: Produces reversible $4Z,15E$-isomers excreted in bile.

• Treatment Thresholds: Plotted on gestational-age and postnatal-hour-specific normograms (e.g., Australian state-based neonatal guidelines such as NSW Health / Safer Care Victoria charts). Thresholds are lower in the presence of risk factors: haemolytic disease, sepsis, acidosis, asphyxia, or serum albumin $< 30\text{ g/L}$.
• Clinical Monitoring: Shield the infant's eyes with opaque eye patches to prevent retinal photochemical damage. Monitor temperature and hydration (insensible water loss increases by 20% to 30%). Serum bilirubin must be measured directly from blood draws; visual inspection and transcutaneous bilirubinometry are invalid once phototherapy is initiated.
• Bronze Baby Syndrome: An asymptomatic grayish-brown discolouration of the skin and urine occurring when phototherapy is inadvertently administered to infants with conjugated hyperbilirubinaemia, caused by photo-oxidation of retained copper porphyrins.

Exchange Transfusion

• Indication: Used when intensive phototherapy fails to arrest a rapid rise in bilirubin (bilirubin rising $> 8.5\text{ to }10\text{ umol/L/hour}$ despite intensive double phototherapy), when total serum bilirubin reaches the designated exchange transfusion line on gestational-age nomograms, or when clinical signs of acute bilirubin encephalopathy develop.
• Technique: Double-volume exchange transfusion ($2 \times 80\text{ mL/kg} = 160\text{ mL/kg}$ for term infants) removes antibody-coated neonatal red blood cells and unbound free serum bilirubin, replacing them with irradiated, crossmatched fresh packed red cells and thawed fresh frozen plasma via an umbilical venous or arterial catheter in aliquots of $5\text{ to }10\text{ mL/kg}$.

Kernicterus & Bilirubin-Induced Neurologic Dysfunction (BIND)

Lipid-soluble unconjugated free bilirubin (unbound to albumin) readily crosses the immature, permeable neonatal blood-brain barrier. Bilirubin is selectively cytotoxic to neuronal mitochondria, causing necrosis and gliosis in the globus pallidus, subthalamic nuclei, hippocampus, oculomotor nuclei, and brainstem auditory nuclei.

• Acute Bilirubin Encephalopathy (ABE):
  • Phase 1 (Early): Lethargy, hypotonia, poor sucking reflex, high-pitched cry.
  • Phase 2 (Intermediate): Stupor, irritability, hypertonia with backward arching of the neck (retrocollis) and trunk (opisthotonos), bulging fontanelle, fever.
  • Phase 3 (Advanced): Deep stupor or coma, persistent retrocollis/opisthotonos, bicycling limb movements, apnoea, intractable seizures, death.
• Chronic Post-Kernicteric Bilirubin Encephalopathy (Kernicterus):
  • Choreoathetoid Cerebral Palsy: Prominent involuntary movements, dystonia, and spasticity.
  • Sensorineural Hearing Impairment: Bilateral high-frequency auditory neuropathy spectrum disorder due to auditory brainstem nucleus injury.
  • Impairment of Upward Gaze: Parinaud-like supranuclear vertical gaze palsy.
  • Dental Enamel Hypoplasia: Greenish staining and pitting of primary dentition.

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Congenital Screening Programs

Australian Newborn Bloodspot Screening (Guthrie Test)

Performed between 48 and 72 hours of life by collecting capillary blood via heel prick onto specialized Guthrie filter paper cards. Testing is delayed until 48 hours to ensure adequate enteral protein intake for metabolic metabolite accumulation (reducing false negatives):

• Congenital Hypothyroidism: Assayed via thyroid-stimulating hormone (TSH). Early levothyroxine replacement within the first 2 weeks prevents permanent severe intellectual disability (severe consequences of untreated congenital hypothyroidism).
• Cystic Fibrosis: Assayed via immunoreactive trypsinogen (IRT). Elevated IRT triggers reflex second-tier cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis (identifying $\Delta F508$ and common mutations). Infants with two mutations or high IRT undergo definitive sweat chloride testing.
• Phenylketonuria (PKU): Autosomal recessive phenylalanine hydroxylase deficiency resulting in hyperphenylalaninaemia. Early dietary phenylalanine restriction prevents neurotoxicity and severe intellectual disability.
• Congenital Adrenal Hyperplasia (CAH): 21-hydroxylase deficiency screened via 17-hydroxyprogesterone (17-OHP), preventing fatal salt-wasting adrenal crisis and shock.
• Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) & Organic Acidaemias: Fatty acid oxidation defects screened via tandem mass spectrometry, preventing hypoketotic hypoglycaemic encephalopathy and sudden infant death.

Red Reflex Examination (Bruckner Test)

Performed prior to hospital discharge and at every routine health check (6 weeks, 6 months) using a direct ophthalmoscope set to zero dioptres viewed at an arm's length ($0.5\text{ to }1.0\text{ metre}$) in a darkened room.

• Normal Finding: Symmetrical, equal, bright orange-red pupillary reflection transmitted from both fundi.
• Leukocoria (White Pupillary Reflex): An abnormal, dull, asymmetrical, or white reflex.
• Critical Differentials:
  1. Congenital Cataract: Opacity of the lens (idiopathic, familial, or TORCH infection—particularly congenital rubella syndrome). Requires urgent referral to a paediatric ophthalmologist for surgical lensectomy before 6 to 8 weeks of life to prevent irreversible stimulus-deprivation amblyopia.
  2. Retinoblastoma: The most common primary intraocular malignancy of childhood (caused by somatic or germline mutations in the $RB1$ tumour suppressor gene on chromosome 13q14). Emergency paediatric ophthalmology and oncological referral is required to prevent local extraocular spread, metastasis, and death.
  3. Other causes: Retinopathy of prematurity (ROP), Persistent fetal vasculature (PFV), Coats disease, Toxocariasis.

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Clinical comparison: Differential Diagnosis and Management of Neonatal Jaundice

• Haemolytic jaundice: Intensive phototherapy and exchange thresholds follow the age/gestation/risk nomogram. IVIG is reserved for selected immune-haemolysis cases after specialist review, not routine jaundice treatment. Use total bilirubin for treatment thresholds without subtracting the direct fraction.
• G6PD Deficiency: Age of Onset: Days 1 to 4; Bilirubin Type: Unconjugated; Stool & Urine Colour: Normal yellow stool; clear urine; Key Diagnostic Investigations: G6PD enzyme assay (after haemolysis settles), Heinz bodies on blood film; Primary Management Strategy: Phototherapy, exchange transfusion; avoid oxidative medications, fava beans, mothballs
• Physiological Jaundice: Age of Onset: Days 2 to 4; Bilirubin Type: Unconjugated; Stool & Urine Colour: Normal yellow stool; clear urine; Key Diagnostic Investigations: Total serum bilirubin plotted on postnatal age-specific normogram; Primary Management Strategy: Observation, maintain adequate enteral feeding, phototherapy if crossing threshold
• Congenital Hypothyroidism: Age of Onset: Days 7 to 28; Bilirubin Type: Unconjugated or mixed; Stool & Urine Colour: Normal or pale stool; normal urine; Key Diagnostic Investigations: Serum TSH and free T4, newborn bloodspot card review; Primary Management Strategy: Daily oral levothyroxine ($10\text{ to }15\text{ mcg/kg/day}$) within first 2 weeks of life
• Neonatal Sepsis / UTI: Age of Onset: Any age (1 to 28d); Bilirubin Type: Unconjugated or mixed; Stool & Urine Colour: Variable stool; dark urine if cholestatic; Key Diagnostic Investigations: Full blood count, CRP, blood culture, urine microscopy and culture, LP; Primary Management Strategy: Intravenous ampicillin (or benzylpenicillin) plus gentamicin; supportive fluid resuscitation

Routine well-baby review

A well-baby check combines feeding and family assessment with examination and prevention. Review birth history, growth plotted over time, wet nappies, feeding technique, jaundice and parent concerns. Examine heart and femoral pulses, eyes including the red reflex, hips and neurological tone, and confirm newborn hearing and bloodspot-screen follow-up. A normal screening result does not override a new symptom or poor weight gain. Check immunisations, safe sleep, caregiver mental health and available practical support. Explain safety-net signs such as poor feeding, fewer wet nappies, fever in a young infant, cyanosis or breathing difficulty. Arrange review of any abnormality rather than recording “well” without a follow-up owner. Queensland routine newborn assessment resources describe the examination framework.

Primary references (checked 7 October 2026): ANZCOR newborn ventilation.