The Metabolic Characteristics of Bilirubin in Newborns

Wu jinlinDepartment of Pediatrics

West China Second University Hospital Sichuan University

Baby on Phototherapy

Introduction of Neonatal Jaundice

Jaundice is quite common in neonatal period

[1] 60% of term infants and 80% of preterm infants

[2] Visible jaundice from sclera, mucosa and skin

Introduction of Neonatal Jaundice Can cause serious consequencesconsequences

[1] Actue phase

respiratory failure

bilirubin encephalopathy

neonatal death

[2] lifelong neurologic sequelae— kernicterus

cerebral palsy

epilepsy

mental retardation

auditory and visual disfunctions

Why jaundice is so prevalent

in neonatal period ???

The Metabolic Characteristics of

Bilirubin in Newborns

Normal Bilirubin Metabolism

Y&Z proteinUDPGT

β-glucuronidase

Albumin

shunt bilirubi

n

Enterohepatic Circulation

What’s the distinct metabolic characteristics of bilirubin in

newborns comparing with our adults?

1. Increased bilirubin production in newborns

2. Insufficient binding between bilirubin and albumin

3. Deficient bilirubin conjugation in the hepatocyte

4. Increased enterohepatic circulation of bilirubin

Neonatal Bilirubin Metabolism

5. Others

(1) Increased oxygen partial pressure1. Increased bilirubin production

PO2

PO2

RBC

RBC

bilirubin

[1] Life span of RBC

Preterm: ﹤70 days

Term: 80 days

Adult: 120 days

[2] Turnover rate of neonatal hemoglobin:

2 times faster than that of adults

(2) Short survival of neonatal erythrocyte1. Increased bilirubin production

(3) Over production of shunt bilirubin 1. Increased bilirubin production

heme

bone marrow precusor

shunt bilirubin

1. Increased bilirubin production in newborns

2.Insufficient binding between bilirubin and albumin

3. Deficient bilirubin conjugation in the hepatocyte

4. Increased enterohepatic circulation of bilirubin

Neonatal Bilirubin Metabolism

5. Others

2. Insufficient Binding between Bilirubin and Albumin low content of serum albumin GA albumin

bilirubin-albumin complex

different degree of acidosis at birth binding affinity

B

A

A

A

AB

AB

B

BB B

BB

B

A

B B

B

serum

1. Increased bilirubin production in newborns

2. Insufficient binding between bilirubin and albumin

3.Deficient bilirubin conjugation in the hepatocyte

4. Increased enterohepatic circulation of bilirubin

Neonatal Bilirubin Metabolism

5. Others

3. Deficient Bilirubin Conjugation in the Hepatocyte

UDPGTreaches the adult’s values 1 week after birth

Y carrier proteinincreases rapidly 5~10 days later

conjugation of bilirubin with glucuronic acid

1. Increased bilirubin production in newborns

2. Insufficient binding between bilirubin and albumin

3. Deficient bilirubin conjugation in the hepatocyte

4.Increased enterohepatic circulation of bilirubin

Neonatal Bilirubin Metabolism

5. Others

4. Increased Enterohepatic Circulation of Bilirubin

intestinal flora is not fully developed

abundant β-glucuronidase delayed excretion of meconium

1. Increased bilirubin production in newborns

2. Insufficient binding between bilirubin and albumin

3. Deficient bilirubin conjugation in the hepatocyte

4. Increased enterohepatic circulation of bilirubin

Neonatal Bilirubin Metabolism

5.Others

5. Others

dehydration

acidosis

intracranial hemorrhage

……

cephalohematoma

hunger

hypoxia

Summary

[1] Jaundice is much more frequent in neonates

[2] Pathogenesis : over-production of bilirubin

immature liver function