neonatal jaundice Flashcards
what is jaundice?
-yellow discolouration of skin and sclera due to high levels of bilirubin
how does jaundice tend to appear on neonates?
cephalopods-caudal progression (face to feet)
True/ False Jaundice is physiologically normal in babies
True
how is bilirubin produced?
- from the breakdown of red blood cells and is produced from heme
- heme breakdown produces unconjugates bilirubin which mostly circulates bound to albumin
how does bilirubin travel in the body?
- unconjugated bilirubin circulates bound to albumin
- some bilirubin is free in plasma and can pass across the blood brain barrier
is unconjugated bilirubin water soluble or insoluble?
insoluble and so most be metabolised in the liver into conjugated bilirubin which is water soluble to be excreted from the gut
is conjugated bilirubin insoluble or soluble in water?
soluble and so unconjugated bilirubin which is insoluble must be metabolised into soluble conjugated bilirubin which can be excreted from the gut
what does liver metabolism rely on?
-bilirubin uptake via ligandin and then conjugation by uridine diphosphoglucuronyltransferase (UDPGT)
what are the levels like of ligandin and UDPGT in a newborn and what effect does this have?
ligandin=low
UDPGT=low
this means there is less uptake of bilirubin into the liver and so are inefficient at managing bilirubin
what is enterohepatic circulation?
-some newborns revert to unconjugated bilirubin and is recirculated into the blood stream
what enzyme abnormalities may affect bilirubin metabolism?
Gilberts disease
what causes Gilberts disease?
mutation in UGT1A1 gene
what effect does Gilberts disease have?
-reduces bilirubin uridine diphosphate glucuronosyltransferase (bilirubin-UGT) by around 30% and can make jaundice worse
What can high levels of unconjugated bilirubin cause?
-can cross the BBB and cause encephalopathy which can lead to Kernicterus (cerebal palsy related to bile)
when does physiological jaundice appear in neonates?
24-72 hours
when does early jaundice appear in neonates?
0-24 hours
when does late jaundice appear in neonates?
> 14 weeks in term and 21 days pre term
what are some causes of pathological jaundice?
- haemolysis
- sepsis
- metabolic disorders
- liver disease
what causes physiological jaundice in neonates?
- increased production of bilirubin
- foetal RBC have less of a lifespan than adults (2/3rds of an adult)
- babies born with high hematocrit (proportion of red blood cells in their blood)
- babies are often bruised
- decreased uptake and binding of bilirubin in liver cells leading to decreased conjugation (most important)
- increased enterohepatic circulation of bilirubin
is it normal for a baby to jaundice <24 hours of age?
no- it is almost always pathological
what causes early jaundice?
- usually due to haemolysis with excessive production of bilirubin
- can be sepsis or infection
Rarer causes:
- other blood grop incompatibilities
- red cell enzyme defects e.g. G6PD deficiency
- red cell membrane defecrs e.g. hereditary spherocytosis
- hepatitis
what can cause a baby to be born jaundiced?
- severe haemolysis
- hepatitis (unusual)
what may cause haemolysis?
- ABO incompatibility
- Rh immunisation
- sepsis
what is ABO incompatibility?
- a disease that causes haemolysis and so jaundice
- happens when the mothers blood type is O, and her baby’s blood type is A or B
when should hepatitis be considered as a reaon for causing early jaundice?
-if there is substantial elevation of conjugated bilirubin (>15% of the total)
what are investigations of early jaundice?
- total bilirubin concentration (SBR)
- maternal blood group and antibody titres (if Rh negative)
- baby’s blood, Direct Agglutination Test (detects antibodies on the baby’s red cells), the eulation test to detect anti-A or anti-B antibodies on baby’ red cells
- FBC, CRP
- if clinical concern measure conjugated bilirubin
what investigations should be done for suspected haemolysis?
- blood group incompatibility (most commonly Rhesus or ABO incompatibility)
- can occur in sepsis but it is rare
- can be due to Glucose 6 phosphate dehydrogenase deficiency
what tests must be done for suspected haemolysis?
Direct Agglutination test (DAT):
- Blood group incompatibilities (most commonly Rhesus or ABO incompatibility) can be identified with a positive DAT
- Sepsis would test negative on DAT
Check infants blood group for comparison with mothers
what test would be done to test for blood group incompatibility such as Rhesus or ABO incompatibility?
Direct Agglutination Test (DAT) and it would be positive
how does bilirubin cause encephalopathy?
it crosses the blood brain barrier (BBB) and affects the brain
how does bilirubin encephalopathy present in neonates?
- lethargy
- poor feeding
- temperature instability
- hypotonia
- arching of the head, neck and back
what may cause serum bilirubin to be too high causing jaundice?
- mild dehydration/insufficient milk supply
- breakdown of extravasated blood e.g. cephalohaematoma, bruising
- some ‘normal’ physiological
- haemolysis (continuing causes as discussed under too early)
- infection
- increased enterohepatic circulation (gut obstruction)
what is the major differential in diagnosis of ‘too long’ pathological jaundice?
-whether the elevated bilirubin is mostly unconjugated or whether the conjugated fraction is substantially increased (>15% of total)
what is the most common cause of unconjugated prolonged jaundice?
breast milk jaundice (cessation of breast feeding is not advised)
what are some causes of persistent unconjugated hyperbilirubinemia causing jaundice?
- breast milk jaundice (most common)
- poor milk intake
- haemolysis
- infection (especially UTI)
- hypothyroidism
True or false conjugated hyperbilirubinaemia can be normal
False- it is always abnormal
can be hepatitis or biliary atresia
what does conjugated hyperbulirubinaemia suggest?
always abnormal
could be biliary atresia or hepatitis
what is biliary atresia?
-a rare disorder causing obstructive jaundice which is fatal if left untreated
how do patients with biliary atresia present?
- usually have pale clay coloured wstool
- dark urine
- jaundiced
what is the treatment for biliary atresia?
-surgery with a Kasai portoenterostomy before 3 months of age
what is the success of the biliary atresia surgery directly related to?
-age of operation
<10 weeks= better chance of bile flow and reduced need for liver transplant
what is the most common causes of unconjugated hyperbilirubinaemia?
- hypothyroidism (most common)
- breast milk jaundice
what is done to detect hypothyroidism that causes unconjugated hyperbilirubinaemia early?
babies are screened for hypothyroidism
what is the treatment for jaundice?
- treat underlying cause if present
- adequate enteral feeding/hydration
- if breast feeding is not established then top up feeds with expresed breast milk is best
- sometimes supplementation with formula will be needed
- occasionally some tube feeding will be required and for seriously unwell babies intravenous fluids
- phototherapy (blue-green range light, make sure eye protection)
- rarely must do an exchange transfusion (usually required for babies with Haemolytic disease)
- IV immunoglobulin (used when bilirubin is increasing even in phototherapy)
what treatment is often required to treat jaundice in babies with haemolytic disease?
-exchange transfusion
what is normal weight loss in neonates?
up to 10%
