Hyperbilirubinemia Flashcards
What is hyperbilirubinemia?
Elevated total serum bilirubin level
What is considered hazardous hyperbilirubinemia?
TSB > 30 mg/dL
What is bilirubin?
A byproduct of RBC destruction which releases heme-containing proteins
What is jaundice?
Yellow color caused by the deposit of bilirubin in the skin
What is acute bilirubin encephalopathy?
Bilirubin toxicity with symptoms correlated to elevated levels of unconjugated bilirubin
What are the phases of acute bilirubin encephalopathy?
Phase 1: lethargy, hypotonia
Phase 2: fever, retrocollis, hypertonia, opisthotonos, high pitched cry
Phase 3: shrill cry, hearing and visual impairment, athetosis, apnea, seizures, coma, death
What is kernicterus?
Irreversible, chronic sequelae of bilirubin toxicity; yellow staining of brain tissue caused by transfer of free bilirubin into brain cells
What is unconjugated bilirubin?
Indirect bilirubin, fat soluble, produced by RBC destruction
What is conjugated bilirubin?
Direct bilirubin, transformed by liver to water soluble form
What is free bilirubin?
Indirect bilirubin which is not bound to albumin
What is the normal bilirubin production in neonates?
8 – 10 mg/kg/day
How does bilirubin bind to albumin?
Bilirubin binds reversibly to albumin; each albumin molecule can bind ~2 molecules of bilirubin
What factors affect bilirubin binding?
- Amount of serum bilirubin
- Albumin levels
- Competition for binding sites
- Drugs such as salicylates, sulfa products
- Acidosis and hypoxemia
What causes kernicterus?
Transfer of free (unbound and unconjugated) bilirubin into brain cells
What is the role of hepatic ligandin?
Transports unconjugated (indirect) bilirubin into the hepatocyte
What is the enzyme responsible for conjugating bilirubin?
Uridine diphosphogluconurate glucuronosyltransferase (UGT)
What is enterohepatic recirculation?
Process where conjugated bilirubin can be broken down into unconjugated bilirubin in the intestine and reabsorbed
What are some causes of hyperbilirubinemia?
- Increased RBC volume
- Increased hematocrit
- Increased RBC destruction
- Infection (bacterial or viral)
- Red cell membrane defects
- RBC enzyme defects (e.g., G6PD deficiency)
- Delayed meconium passage
- Delayed feeding
What is G6PD deficiency?
One of the most important causes of hazardous hyperbilirubinemia; identifying infants is challenging
What is breast milk jaundice?
Hyperbilirubinemia that persists despite adequate intake and weight gain; can last up to 3 months
What are the risk factors for developing significant hyperbilirubinemia?
- Lower gestational age
- Jaundice in the first 24 h after birth
- Family history of phototherapy or exchange transfusion
- Exclusive breastfeeding with suboptimal intake
What characterizes physiologic (non-pathologic) jaundice?
Develops at > 24 hours of age; total bilirubin is < 12 mg%; peaks at day 3-4 (term) or 5-6 (preterm)
What defines pathologic or hazardous jaundice?
Appears at < 24 hours of age (term) or < 48 hours (preterm); persists beyond normal time frame; rate of rise > 0.2-0.3 mg% per hour
What is RhoGAM?
Anti-D human gamma globulin given to mothers to prevent production of anti-Rh(D) antibodies
