Neonatal Hyperbilirubinemia

Question 1

When testing for jaundice, for lab tests you must order

Answer 1

BOTH Direct and Total Bilirubin

Question 2

Total bilirubin includes

Answer 2

Includes Direct and indirect

= TSB (total serum bilirubin)
TcB (total capillary bilirubin)

Question 3

Heme is converted to

Answer 3

biliverdin via heme oxygenate
(Fe2+ and CO are byproducts)

THEN, biliverdin is converted to bilirubin via biliverdin reductase

Question 4

Bilirubin is formed from _______ and is bound to _________

Answer 4

heme catabolism

albumin

Question 5

Bilirubin can cross BBB in

Answer 5

its free state

Question 6

In hepatocytes bilirubin binds to

Answer 6

Z-protein and Ligandin

Question 7

Bilirubin is conjugated with _________ by __________ to make it more water soluble

Answer 7

with glucuronic acid by the enzyme uridine diphosphate glucuronyl transferase

Question 8

Unconjugated bili crosses ________

Answer 8

placenta in fetus – conjugated by maternal liver

Question 9

Most conjugated bili is dumped in to

Answer 9

the gut – excreted by GI tract

some is excreted into the urine

Question 10

__________ further metabolizes conjugated bili

Answer 10

Bacteria flora

Question 11

__________ hydrolyzes bili back into unconjugated form

Answer 11

Beta-glucuronidase (intestinal enzyme)

Question 12

Neonates have excessive _______ and low ________

Answer 12

Beta-glucuronidase and low intestinal flora

Question 13

Risk factors for the development of hyperbilirubinemia in infants of 35 or more weeks gestation

Answer 13

• Elevated predischarge TSB or TcB levels
• jaundice observed in the first 24 hrs or prior to discharge
• Blood group incompatibility with positive direct antiglobulin test, other known hemodynamic disease (G6PD deficiency, hereditary spherocytosis)
• decreasing gestational age
• previous sibling with jaundice or who received phototherapy
• vacuum extraction during deliver, cephalhematoma or significant bruising
• Exclusive breastfeeding, particularly if nursing isn’t going well and weight loss is excessive
• East Asian race
• Macrosomic infant or diabetic mom
• Maternal age over 25
• Male gender

Question 14

Physiologic Jaundice

Answer 14

• Unconjugated hyperbilirubinemia that occurs after the first postnatal day and can last up to 1 week
• Term infants peak in the first 3 to 5 postnatal days.
• Preterm infants peak at 5-7 days.
• If > than 15 at any time no longer physiologic

Question 15

During physiologic jaundice, bilirubin production is increased as a result of

Answer 15

elevated hematocrit and red blood cell volume per body weight and a shorter life span of the red blood cells.

-Infants also have immature hepatic glucuronyl transferase (UDP-GT)

Question 16

Pathogenesis of jaundice associated with breast feeding

Answer 16

• increased enterohepatic circulation of bilirubin
• decreased caloric intake
• less cumulative stool output and stools contain less bilirubin (compared to formula fed infants)
• increased intestinal fat absorption
• less formation of urobilin in GI tract
• increased activity of beta glucuronidase in breast milk
• decreased bilirubin conjugation (mutations of the UGT1A1 gene, Gilbert’s syndrome–prolonged breast milk syndrome)