The Metabolic Characteristics of Bilirubin in Newborns Wu jinlin Department 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 consequences  Can cause serious consequences [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 protein UDPGT β-glucuronidase Albumin shunt bilirubin 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 pressure 1. Increased bilirubin production PO 2 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 erythrocyte 1. 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 A B A B B B B B B B 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  UDPGT reaches the adult’s values 1 week after birth  Y carrier protein increases 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

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