How to know if bilirubin is damaging the brain?
At what level of bilirubin will brain damage occur in my baby?

This is hard to know for the individual case. It depends on how much albumin is in the blood to bind the bilirubin and keep it in the blood and out of the brain. It depends on how mature or healthy the baby is. It depends on what is the cause of hyperbilirubinemia. Finally, there could theoretically be genetic differences in the ability of some baby's brains to resist exposure to bilirubin.

What we can say is that ABE begins to occur when the baby shows signs and symptoms of AB as outlined above. However when that occurs in most babies depends on a number of factors including just stational age parenthesis prematurely or term, cause of the hyperbilirubinemia, other conditions such as acidosis Dash high levels of acid in the blood, for hemolysis. There are some causes of hyperbilirubinemia such as Rh disease or severe G6PD deficiency that cause blood to rapidly hemolyze that present more risk at any given level of bilirubin in the blood. Hemolysis means the red blood cells are breaking down and releasing hemoglobin, which is being converted to bilirubin. If this is happening rapidly, it is harder for the baby's bodies to get rid bilirubin quickly enough, and is therefore it can be more dangerous to the brain.

That all being said, there are guidelines available from the American Academy of Pediatrics that have been adopted pretty much worldwide. These are guidelines for when treatment is indicated for hyperbilirubinemia. There are guidelines for using phototherapy to gradually reduce the level of bilirubin by converting toxic unconjugated bilirubin (UCB) to a form of bilirubin that can be eliminated by the kidneys. There are also guidelines for doing a double volume exchange transfusion, a more drastic treatment to rapidly reduce the bilirubin level in the blood and also to remove antibodies against red blood cells, such as in Rh disease or ABO.  Note that a double volume exchange transfusion, often just called an exchange transfusion, is not to be confused with a simple blood transfusion.  These AAP guidelines are meant to be well below levels where the bilirubin will escape from the blood and cause brain damage. Thus, most clinicians most experienced clinicians, pediatricians and neonatologists have set levels where they feel that if the bilirubin doesn’t go higher there will be no brain damage. These guidelines were published in 2004 and can be seen below. Note that that the two treatment guidelines, phototherapy and exchange transfusion, are given for three different risk groups that are defined, since there is more risk for a premature baby or a baby who is sick or has risk factors than a healthy full-term baby. The Guidelines are currently being revised by the AAP.

The Jaundiced Baby with a high Bilirubin and NO Signs of ABE (Acute Kernicterus)

For babies who are term (37 to 42 weeks gestation) or near-term (premature but ≥ 35 weeks gestation) and without any other known risk factors, the bilirubin should be plotted on a nomogram (graph) such as the hour-specific “Bhutani nomogram” to see what percentile it is in (Figure 1). This nomogram predicts the likelihood that the baby’s bilirubin will reach a level of 17 mg/dL, a level that should be treated according to the AAP 2004 Guidelines.

If the percentile is high on the nomogram above, then recommendations for treatment are founnd  in the AAP 2004 Guidelines to determine if the baby needs treatment with either phototherapy or exchange transfusion. The AAP Guidelines tell when to treat a term or near-term baby with phototherapy (Figure 2) or with an exchange transfusion (Figure 3), taking into consideration whether the child is premature and has other risk factors.

The cause of the jaundice should be determined.  Measures to increase feeding and hydration, e.g. lactation counseling and increased breast-feeding and/or temporary supplementation should be considered. Home phototherapy with a phototherapy blanket ("biliblanket") might be prescribed, but levels must be closely followed since the amount of phototherapy delivered by home systems is relatively small. Even though a baby may not show signs of acute kernicterus the child may still be in danger. It is essential that all jaundiced children have their bilirubin levels tested and plotted against the Bilirubin Nomogram (see figure above) to assess the current risk level. However, note that there are some conditions for which the nomogram does not apply, for example prematurity more than 4 weeks early (less than 36 weeks gestation), hemolysis including G6PD deficiency, Rh disease, hereditary conditions especially of red blood cells (e.g., spherocytosis, elliptocytosis) and other conditions.

The age of the child (in hours after birth) directly affects the level of risk, so a bilirubin level may be considered “at risk” at an early time but “safe” at a later time. The bilirubin should be plotted on a nomogram such as the Bilirubin Nomogram (see Figure 1) to see what at-risk percentile the child is currently at. This percentile gives the risk that the bilirubin will rise to a level that should be treated, generally 17 mg/dL (or 290 µM). Note also that there are intenet apps that you can use that you enter information and will give you the risk zone (low, low intermediate, high intermediate and high). I like the one called BiliTool (www.bilitool.org) that is based on the nomogram in the 2004 AAP Guideline pictured above.

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Figure 1. Nomogram for designation of risk of reaching a level of 17 mg/dL, near the level that the AAP recommends treating low-risk babies with phototherapy (see Figure 2).

Treatment Guidelines for Newborns with Hyperbilirubinemia

In most circumstances, treatment guidelines based on current recommendations should be followed according to the current AAP guidelines for starting phototherapy or, in more extreme cases, a "double volume blood exchange transfusion".

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The charts here (Figures 2 and 3) from the 2004 American Academy of Pediatrics (AAP) Guidelines, give recommendations for treatment of jaundiced newborn babies more than 35 weeks gestational age with phototherapy (Figure 2) or double volume exchange transfusion (Figure 3) for hyperbilirubinemia.

 

Phototherapy is used to prevent bilirubin from going higher and gradually lower bilirubin but converting the structure of toxic unconjugated bilirubin to a compound that can be excreted by the kidneys. 

A double volume exchange transfusion is a more extreme and immediate form of treatment that lowers bilirubin levels quickly in case are antibodies destroying the baby's red blood cell tool quickly, such as in Rh disease or ABO blood group incompatibility. 

Note that 40 weeks is normal gestation, so this means that these charts are meant for babies not more than 5 weeks premature, that is or not less than 35 weeks gestational age. Also, the different lines are used for different categories of babies based on other risk factors described in the text underneath the graphs.

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Figure 2. Guidelines for phototherapy  in infants 35 or more weeks’ gestation.

Figure 3. Guidelines for exchange transfusion in infants 35 or more weeks’ gestation.

Some Final Thoughts about Treatment of Hyperbilirubinemia

The cause of the jaundice should be determined if possible in order to prevent further elevation of bilirubin. Because bilirubin leaves the body through normal elimination of waste in urine and stool, measures to increase feeding and hydration, e.g. lactation counseling and increased breast-feeding and/or temporary supplementation should be considered. Expert neonatologists say that the most common cause of bilirubin levels rising high enough after discharge from the hospital to require readmission is inadequate feeding. Home phototherapy with a phototherapy blanket ("biliblanket") may be prescribed, but bilirubin levels must be closely followed since the amount of phototherapy delivered by home systems is relatively small. Putting the baby in the sunlight is not recommended because the dose of phototherapy is small, and there is the added risk of sunburn.

For babies who are term (37 to 42 weeks gestation) or near-term (premature but ≥ 35 weeks gestation) and without any other know risk factors, the bilirubin should be plotted on a nomogram (graph) such as the hour-specific “Bilirubin nomogram” to see what percentile it is in (Figure 1). This nomogram predicts the likelihood that the baby’s bilirubin will reach a level of 17 mg/dL, a level that should be treated according to the American Academy of Pediatrics AAP 2004 Guidelines.

 

If the percentile is high on the nomogram above, then recommendations for treatment are founnd with the AAP 2004 Guidelines to determine if the baby needs treatment with either phototherapy (Figure 2) or double volume blood exchange transfusion (Figure 3). The AAP Guidelines tell when to treat a term or near-term baby with phototherapy or an exchange transfusion taking into consideration whether the child is premature and has other risk factors.