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Dr. Jeff Hersh: Watch newborns for jaundice

Dr. Jeff Hersh

Q: My 2-day-old nephew's skin became yellow and they kept him in the hospital under lights in an incubator. What is this all about?

A: Jaundice is when someone's skin and the whites of their eyes (sclera) become yellow from a build-up of bilirubin in the blood.

When red blood cells break down, the body tries to recycle the iron from their hemoglobin, and bilirubin is a byproduct of this recycling effort.

Almost all bilirubin is bound to a protein (albumin) in the blood and is brought to the liver to be processed by an enzyme so the final byproducts can be excreted in bile and urine.

Bilirubin can build up either from increased production or decreased clearance. Both occur, to some extent, in all newborns, so essentially all develop a level above the normal adult level. Hence "physiologic" neonatal jaundice (a slight yellow pigmentation) is extremely common.

A newborn's red blood cells' lifetime is shorter than an adult's (85 vs. 120 days) and the concentration of red blood cells is higher (50 to 60 instead of 40 to 50), so red blood cell turnover (and, hence, bilirubin production) is higher.

If there is an immune response destroying the baby's red blood cells -- for example, due to blood type or Rh incompatibility -- abnormal red blood cell types (such as spherocytosis), certain enzyme problems (such as G6PD deficiency), or increased red blood cell destruction from infection or from hematomas (bruises from the birth process), bilirubin levels can become extremely high.

Neonatal decreased bilirubin breakdown occurs since a newborn's UGT level is only 1 percent of an adult level, which is not achieved until age 3 1/2 months.

There can also be inherited conditions -- such as Crigler-Najjar or Gilbert syndromes- - that decrease breakdown, as well as certain liver or gastrointestinal conditions.

Finally, other contributing factors (such as breast milk's lower beta-glucuronidase level, dehydration or thyroid dysfunction) can raise bilirubin levels.

Although elevated bilirubin is suspected based on physical exam (the yellow discoloration starts in the face/forehead, and then spreads to the torso and eventually the extremities) other tests (probes that can estimate the level through intact skin or a definitive blood test) may be needed to verify the specific level.

Factors that should raise the suspicion of very elevated bilirubin include jaundice within 24 hours or after two weeks of birth, rapidly rising bilirubin levels, a sibling having required treatment for elevated bilirubin, excessive bruising and/or premature birth. Some experts recommend a blood bilirubin test for all newborns. The bilirubin level needs to be interpreted in light of the baby's age in hours (since bilirubin levels typically rise for the first couple of days of life) and their risk factors.

If bilirubin levels are very elevated, other tests such as total blood count, evaluation for autoimmune blood destruction or G6PD enzyme deficiency, and even liver or thyroid tests may be indicated.

Slightly elevated bilirubin levels cause only yellow skin/sclera discoloration. However, since the small percentage of bilirubin not bound to albumin can cross the blood/brain barrier, very elevated bilirubin levels can lead to bilirubin-induced neurologic dysfunction. Symptoms of this can range from drowsiness to more pronounced neurological dysfunction, such as decreased ability to feed and even seizures.

The most concerning complication of increased bilirubin is permanent brain damage (kernicterus) possibly leading to hearing loss, eye or teeth problems, mental retardation and even cerebral palsy-like symptoms. Appropriate treatment and giving moms with Rh negative blood a shot of Rhogam (to prevent one type of immune reaction red blood cell destruction in subsequent pregnancies) has helped lead to a decline in the incidence of kernicterus to only 1 or 2 cases per 100,000 U.S. births.

Neonatal bilirubin levels high enough to require treatment (to prevent BIND/kernicterus) occur in about 5 percent of babies.

Phototherapy (shining light on the baby) can help convert bilirubin to the more soluble isomer lumirubin, hence increasing excretion in urine and bile. Furthermore, lumirubin cannot cross the blood/brain barrier, so the risk of BIND/kernicterus is immediately decreased. The specific wavelength and strength of the light used, as well the illuminated area of the baby's skin, will determine the effectiveness of phototherapy. Treated babies should be in just a diaper to increase skin coverage, have eye protection and be adequately hydrated.

Extremely elevated bilirubin not responding to phototherapy may require exchange transfusion (removing some of the bilirubin-laden blood and transfusing replacement blood). Possible complications of this therapy include a small risk of infection, lowering platelets, graft vs. host disease, electrolyte imbalances and others. Elevated bilirubin due to an immune reaction may be helped by immunoglobulin infusion.

All babies should be screened for elevated bilirubin with a physical exam and possibly a blood test while in the hospital. Once discharged they should have a follow-up visit with their health care provider within two days to be rechecked.

Massachusetts-based Dr. Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.