Neonatology Flashcards
What are the two most common causes of neonatal jaundice?
And explain the pathophysiology behind them.
- Phsyiological jaundice: Increased haematocrit and decreased RBC lifespan, immature glucoronyl transferase enzyme system (slow conjugation of bilirubin), increased enterohepatic circulation.
- Breast milk jaundice: due to lack of milk production and subsequent dehydration, leading to exaggerated physiological jaundice.
What are the causes of neonatal jaundice by age?
Describe the pathophysiology of jaundice?
- Jaundice is bilirubin that is deposited in the skin and mucous membranes.
- Bilirubin is the end product of haem breakdown.
- Lysis of red blood cells release haem from haemoglobin, haem is then converted to bilirubin and excreted.
What are the two forms of bilirubin and how do they move throughout the body?
- Unconjugated bilirubin reversibly bound to albumin
- Conjugated bilirubin readily excretable via the renal biliary systems.
When is jaundice pathological?
- Within the first 24 hours
- Conjugated hyperbilirubinaemia
Describe how you can estimate the amount of bilirubin causing neonatal jaundice?
What is the prevalence of neonatal jaundince in term and preterm infants?
- 65% of term newborns develop clinical jaundice in first week
- 80% of preterm infants
What investigations need to be ordered when working up a neonate for jaundice?
- FBC, film and reticulocytes
- Serum bilirubin levels
- Blood group
- Maternal blood group
- Direct coombs test
- Consider G6PD level
What factors increase the severity of physiological jaundice in neonates?
- Prematurity
- Sepsis
- Bruising
- Cephalohaematoma
- Polycythaemia
- Delayed passage fo neconium
- Breast feeding
- Genetics - certain ethnic groups, esp Chinese
What Ix need to be ordered in a neonate that has prolonged jaundice?
- Serum bilirubin level
- Conjugated fraction of bilirubin
- LFT
- Coags
- Abdo US _ gallbladder
- DISIDA/HIDA scan (with follow through)
- Hepatitis screen (TORCH)
- Liver biopsy (bile duct proliferation)
- TFT
- Metabolic screen (urine for reducing substances)
- PLUS usual tests:
- FBC, film, retics
- Blood group
- maternal blood group
- direct coombs test
What are the complications of neonatal jaundice?
Kernicterus: bilirubin encephalopathy
- Is a neurological syndrome resulting from neurotoxic effects of unconjugated bilirubin on basal ganglia and brainstem nuclei.
- Unconjugated bilirubin is lipophilic and can cross the blood-brain barrier
- Signs and symptoms of kernicterus (first 24 hours)
- Phase 1: Poor sucking, hypotonia and lethargy
- Phase 2: Hypertonia and opisthotonos (severe tetanus)
- Phase 3: Less hypertonia, high pitched cry, hearing and visual loss, poor feeding and athetosis (involuntary writhing movements)
- Long term: Choreoathetoid cerebral palsy, Sensorineural hearing loss, upward gaze palsy, intellectual delay.
What is the treatment for neonatal jaundice?
Depends on the cause and the level and type of bilirubin:
- Unconjugated:
- Ensure adequate fluid intake
- Phototherapy
- IV immunoglobulin
- Exchange transfusion
- Conjugated:
- Ensure adequate nutrition
- Treat underlying problem
HOw does phototherapy work?
- Phototherapy converts unconjugated bilirubin into an isomer that is soluble and can be excreted by the liver without conjugation.
- Many wavelengths from 420-600nm of light do this (blue, green and white)
- IT IS NOT UV light
- Blue light is the most effective
What are the factors that determine efficacy of phototherapy?
- Wavelength (type of light source)
- Distance to baby: maximise irradiance by minimising patient to light source distance.
- Skin area exposed: Maximise for intensive phototherapy with additional light source below infant
- Irradiance: the flux of energy per unit area
- Time: more time better
When do you start phototherapy?
- Decision is based on:
- Level of bilirubin
- RAte of rise of bilirubin
- Gestational age
- Chronological age
- Wellness of the baby
- There are charts to help with this so don’t need to know the specifics
What are the complications of phototherapy?
- Retinal degeneration
- Temperature instability
- Fluid balance - dehydration
- ↑ insensible and intestinal water losses
- Loose frequent stools
- Bronze-baby syndrome - retention of bile pigment photoproducts these are toxic metabolites.
How does exchange transfusion works for neonatal jaundice?
- Doubles volume - 160 mls/kg
- Removes 80% of RBCs
- Removes 50% of bilirubin
- Used:
- Group O (Kell-negative)
- RhD - idential with the baby
- <5 days old
- CMV negative (or at least WBC depleted)
- Irradiated (to prevent GVHD)
What are the complications of exchange transfusion?
- INfection
- Thromboembolic events
- Acid-base, electrolyte and glucose distrubances
- Coagulation and platelets disturbances
- Hypothermia
- Transfusion reaction
- Complcations from the line used