小兒科雜記Pediatrics topic 1: Unconjugated hyperbilirubinemia in the newborn

Unconjugated hyperbilirubinemia in the newborn

0. Metabolism process review
-- Heme-->[heme oxygenase]-->biliverdin-->[biliverdin reductase]-->bilirubin-->[UGT1A1]-->conjugated bilirubin-->[beta-glucuronidase]-->unconjugated bilirubin

1. Total bilirubin:
-- usually > 1mg/dL
               # hematocrit 50~60% (more RBC)
               # shorter life span of RBC (85 days)
               # deficient UGT1A1

               # increased enterohepatic circulation

-- can reach 10~14 mg/dL @ 3~5 days old (East-Asians) 
-- resolves within the first one to two weeks after birth
-- >25 mg/dL:  bilirubin-induced neurologic dysfunction (BIND)--> kernicterus


2. Neonatal hyperbilirubinemia (>35 wks)
-- check hour-specific Bhutani nomogram: >95th percentile
-- severe if
             # appear at first 24 hrs
             #  >95th percentile
             # 0.2 mg/dL ↑ per hour
             # after 2 weeks
             # conjugated >1 mg/dL or >20 percent

3. Breast milk jaundice
-- >5 mg/dL for several weeks (max. 12 wks)
-- etiology: some unknown factor in milk promoting enterohepatic circulation

4. Breast feeding failure jaundice
-- combined with low output (urine+stool), hypovolemia, weight loss