Treatment of Jaundice ✅ Flashcards
What does the type of treatment for jaundice depend on?
- Bilirubin level
- Rate of rise of bilirubin
- Gestational age
- If other risk factors are present
What are current treatment thresholds for jaundice in neonates based on?
Consensus guidelines (NICE and AAP) - not evidence based
Is the albumin-bilirubin ratio used when determining treatment for neonates?
No
Why is the albumin-bilirubin ratio not used when determining treatment for neonates?
Most laboratories overestimate albumin, especially at low concentrations
Is management of jaundice based on total or conjugated bilirubin levels?
Total
Why is management of jaundice based on total bilirubin level?
There are rare cases of kernicterus with high conjugated bilirubin levels, and a theoretical risk that conjugated bilirubin can elevate free bilirubin levels
In theory, how can conjugated bilirubin cause an increase in free bilirubin?
By displacing unconjugated bilirubin from the binding sites
How does phototherapy work?
Through geometric photoisomerisation of unconjugated bilirubin
What is the normal bilirubin isomer?
4Z, 15Z
What wavelength of light is used in phototherapy?
460 +/- 10nm
What happens to bilirubin when it absorbs light of the specific wavelength used in phototherapy?
The light is absorbed and the bilirubin undergoes Z to E isomerisation
How does the E isomer of bilirubin differ from the Z isomer?
The E-isomer is more polar and water-soluble than the Z-isomer
What is the result of the E-isomer of bilirubin being more polar and water-soluble?
It can be excreted without conjugation
Other than the E-isomer of bilirubin, what else is produced when the Z-isomer absorbs light in phototherapy?
A small amount of structural isomer (lumirubin)
How is lumirubin formed in phototherapy?
Photo-oxidation
What does the effectiveness of phototherapy depend on?
- Wavelength
- Irradiance (dose of light)
- Exposed body surface area
- Distance from light source
- Duration of treatment
What irradiance is optimal in phototherapy for jaundice?
30-40mwatts/cm^2/nm
What colour of light is most effective in phototherapy for jaundice?
Blue or blue-green light
What is the wavelength of blue/blue-green light?
230-490nm
How is intensive phototherapy achieved?
- Using more than 1 light source
- Bulbs held at close distance
- Well-exposed body
How do the measures used to provide intensive phototherapy maximise the effectiveness?
By increasing irradiance
Why is insensible water loss during phototherapy now less of an issue than previously?
Increased used of LED lights that have a lower heat output
What medications can be used in the treatment of jaundice?
- Phenobarbitone
- Metalloporphyrins
- IV immunoglobulin
How does phenobarbitone work in jaundice?
- Induces hepatic UGT enzyme and hence the conjugation of bilirubin
- May also increase hepatic uptake of bilirubin
What is the limitation of the use of phenobarbitone in jaundice?
Acts very slowly, doesn’t lower serum bilirubin levels fast enough to be clinically helpful
Which metalloporphyrins may help in jaundice?
Tin and zinc
How do tin and zin protoporphyrins work in jaundice?
They inhibit haem oxygenate
Why does the inhibition of haem oxygenase help in bilirubin?
It is the rate limiting step in the production of bilirubin for haem
Are metalloporphyrins used clinically?
Their use is under investigation, and currently not recommended
Which patients with jaundice might benefit from IVIG?
Neonates with rhesus or ABO immune haemolytic disease
What is the benefit of IVIG for jaundice in neonates with rhesus or ABO haemolytic diease?
- Reduces bilirubin levels
- Reduces need for exchange transfusion
When is IVIG recommended in jaundice caused by rhesus or ABO haemolytic disease?
As an adjunct to intensive phototherapy if serum bilirubin continues to increase more than 8.5µmol/L/hour
What is the mechanism of action of IVIG in jaundice caused by rhesus or ABO immune haemolytic disease?
Non-specific blockage of Fc receptors, which reduces red blood cell breakdown
Why does the specific blockade of Fc receptors reduce RBC breakdown in rhesus or ABO haemolytic disease?
In isoimmune haemolysis, RBC are destroyed by an antibody-dependent cytotoxic mechanism mediated by Fc receptor-bearing cells of the neonatal reticuloendothelial system
Can maternal IVIG administration reduce fetal haemolysis in rhesus or ABO immune haemolytic disease?
Yes
When is exchange transfusion used?
Severe hyperbilirubinaemia
What is the purpose of exchange transfusion in severe hyperbilirubinaemia?
- Prevent kernicterus
- Remove haemolytic antibodies
- Correct anaemia
What does exchange transfusion involve?
Removing aliquots of neonatal blood and replacing it with donor blood
How much is the serum bilirubin reduced by following a double volume exchange transfusion?
50%
What has happened to the need for exchange transfusion?
It has been markedly reduced
Why has the need for exchange transfusion been markedly reduced?
- Prevention and prenatal treatment of Rhesus disease
- Early treatment of jaundice with phototherapy
What is the morbidity when exchange transfusion is required for jaundice?
5%
What is the mortality when exchange transfusion is required for jaundice?
0.3%
What causes morbidity and mortality in exchange transfusion?
- Biochemical and haematological disturbances
- Vascular accidents
- Cardiac complications
- Sepsis
