Neonatal Hyperbilirubinemia Flashcards Preview

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Flashcards in Neonatal Hyperbilirubinemia Deck (16)
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When testing for jaundice, for lab tests you must order

BOTH Direct and Total Bilirubin


Total bilirubin includes

Includes Direct and indirect

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


Heme is converted to

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

THEN, biliverdin is converted to bilirubin via biliverdin reductase


Bilirubin is formed from _______ and is bound to _________

heme catabolism



Bilirubin can cross BBB in

its free state


In hepatocytes bilirubin binds to

Z-protein and Ligandin


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

with glucuronic acid by the enzyme uridine diphosphate glucuronyl transferase


Unconjugated bili crosses ________

placenta in fetus – conjugated by maternal liver


Most conjugated bili is dumped in to

the gut – excreted by GI tract
(some is excreted into the urine)


__________ further metabolizes conjugated bili

Bacteria flora


__________ hydrolyzes bili back into unconjugated form

Beta-glucuronidase (intestinal enzyme)


Neonates have excessive _______ and low ________

Beta-glucuronidase and low intestinal flora


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

-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


Physiologic Jaundice

-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


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

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)


Pathogenesis of jaundice associated with breast feeding

-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)