Does this baby need phototherapy?

Phototherapy and exchange transfusion nomograms Posted by Ahmad Azizov on July 18, 2020

Does this baby need phototherapy?

Babies can have high levels of bilirubin just after birth. Some of this excess bilirubin is due to physiological jaundice and does not require active treatment. The main causes of physiological jaundice include higher red cell turn over (due to fetal hemoglobin to adult hemoglobin conversion) and low levels of bilirubin-conjugating enzyme uridine diphosphoglucuronyltransferase. Bilirubin levels can exceed these physiological levels in conditions such as prematurity, gestational diabetes in mom, G6PD deficiency in baby, blood incompatibility with mom and baby, and many others. Untreated hyperbilirubinemia can lead to the development of kernicterus in babies which is characterized by mild to severe brain damage and even death. Younger babies are at a greater risk for developing kernicterus due to their still-developing blood-brain barrier

Picture 1. Hyperintense basal ganglia lesions on MRI

Babies who have high bilirubin levels at birth and whose bilirubin keeps trending up, kernicterus becomes a serious concern. To lower the levels of bilirubin and prevent kernicterus phototherapy was developed. With the help of visible spectrum blue light (frequency of 460-490 nm) bilirubin can be converted into compounds that are soluble in the infant's urine and stool without having to be conjugated by the liver. Graph 1 below was developed to risk stratify babies with jaundice and provide phototherapy to babies who are at the highest rate to develop kernicterus. 

Graph 1. If the baby's serum bilirubin falls above the curve for his/her given risk factors and gestational age, then phototherapy is initiated. 

Babies who are premature (<38 weeks) and have one of the risk factors from Table 1, are at a higher risk to develop kernicterus and therefore require a lower threshold (gray curve) to initiate phototherapy. Conversely, a baby who is born after 38 weeks with no maternal or baby risk factors can tolerate a higher rate of bilirubin and therefore does not need to be put on phototherapy as early (blue curve). 

Table 1. Factors that increase the baby's chances for developing kernicterus (and therefore lower the curve for photo-therapy initiation)
Risk factors Explanation
G6PD deficiency  Red blood cell abnormality that leads to increased hemolysis and hyperbilirubinemia 
Previous sibling requiring phototherapy  
Asian race   
Positive Coombs/DAT test  This test is done on the umbilical cord blood. Mother's antibodies can attack the baby's red blood cells for a number of reasons. ABO or Rh incompatibility or antibodies in the mother's blood are common causes leading to hemolysis in the baby with a positive Coombs or DAT test. 
Cephalohaematoma or significant bruising Can be caused by vacuum delivery or head injury during the cardinal movements of labor 
Asphyxia   
Sepsis   
Acidosis   
Albumin < 30g/L   
Temperature instability   
Gestational diabetes in mother  
Significant lethargy   

While phototherapy has been initiated, it is essential to investigate the baby for the risk factors from table 1

Direct/conjugated bilirubin

Due to the aforementioned reasons (increased red cell breakdown and premature liver), most of the bilirubin causing jaundice in infants is unconjugated/indirect bilirubin. However, if physicians are unable to find the cause of jaundice in an infant with hyperbilirubinemia, sometimes direct bilirubin is ordered in addition to total serum bilirubin. Unlike unconjugated hyperbilirubinemia, conjugated bilirubinemia is always pathological. Conditions such as biliary atresia result in increased conjugated bilirubin levels because even though the liver can conjugate the amount of bilirubin produced, it is unable to excrete the conjugated bilirubin due to an obstruction.  

Picture 2. Biliary atresia can result in conjugated hyperbilirubinemia 

95% of infants with biliary atresia will require surgical treatment. One important way to differentiate biliary atresia from other causes of neonatal jaundice is by looking at urine and still colors. Biliary atresia patients will have a pale stool and dark urine as conjugated bilirubin is forced to be excreted through the kidneys, instead of bile. There can also be failure to thrive as the baby is unable to absorb fat and fat-soluble vitamins without sufficient bile flow. Vitamin K (fat-soluble vitamin) deficiency can lead to bleeding disorders. Unlike other forms of jaundice, biliary atresia almost never leads to kernicterus, because conjugated bilirubin cannot cross the blood-brain barrier.   

What if phototherapy is not working?

Unfortunately, phototherapy may not always put a baby with hyperbilirubinemia under their respective curves (in the low-risk zone). In these instances, there are a number of other interventions that can be tried. 

  • IV Immune Globulin (IVIG)
    • Made out of a mixture of antibodies derived from blood plasma 
    • Given to babies who have failed to recover from hyperbilirubinemia despite being on phototherapy 
  • Exchange transfusion 
    • This therapy replaces the newborn's blood with a donor's blood and therefore gets rid of the excess bilirubin
    • Similar to phototherapy there is a different monogram (Graph 2for exchange transfusion that risk stratifies infants with hyperbilirubinemia and decides who requires this procedure to prevent kernicterus 
    • Same risk factors from table 1, determine which threshold level will be used to determine the need for exchange transfusion

Graph 2. If the baby's serum bilirubin falls above the curve for his/her given risk factors and gestational age, then exchange transfusion is initiated. 

Examples 

Picture 3. Baby receiving phototherapy for neonatal jaundice

Example 1:

  • A baby boy born at 38 weeks and 5 days to a caucasian mother with type O+ blood type has a 24-hour total bilirubin level of 170μmol/L. The mother has no serum antibodies. DAT test is negative. The baby's blood type is A+ and had a sibling who required phototherapy previously. Labour itself had no complications. Does this baby require phototherapy?

Solution 

  • This is a baby who is born after 38 weeks and who has at least 2 risk factors (previous sibling requiring phototherapy and ABO blood incompatibility) and who has 24-hour bilirubin of 170μmol/L. This means the phototherapy threshold curve we will be using is the medium-risk curve. (Note that the number of risk factors does not lower the threshold. One or more risk factors will lower the threshold by a maximum of 1 risk level). 170μmol/L puts this baby above the medium-risk curve and therefore this baby should be started on phototherapy. If this boy had no risk factors, our decision would be based on the low-risk curve and phototherapy would not be needed. (Also note that DAT/Coombs test is only done if the mother has type O blood with a baby that has A or B type blood or if the mother has positive serum antibodies)

Example 2:

  • A baby girl born at 36 weeks and 3 days to an Asian mother with type A+ blood has a 72-hour total bilirubin level of 200μmol/L. The mother has no serum antibodies. The baby's blood type is O+ and has no other risk factors. Labour was uneventful. Does this baby require phototherapy?

Solution 

  • Looking at all the three thresholds, total bilirubin of 200μmol/L at 72 hours is below all the 3 risk levels and will therefore not require phototherapy at this time. The curve to follow in the future for this baby would be the medium risk curve, because 1. This baby was born prematurely (<38 weeks) and 2. There are no other risk factors. 

Example 3:

  • A baby boy born at 39 weeks and 4 days to an African American mother with A- blood type has a 48-hour total bilirubin of 250μmol/L. The mother has anti-D serum antibodies. DAT test is negative. The baby's blood type is AB- and has no other risk factors. Labour was uneventful. Does this baby require phototherapy? 

Solution 

  • This is a male baby who is born after 38 weeks. You might be tempted to say that his risk level is medium, because of the ABO incompatibility (after all AB- blood cannot be transfused into an individual with A- blood). However, in this case, there is no ABO incompatibility. ABO incompatibility only occurs in mothers who have O+ or O- blood type with a baby with non O blood type. Because of this, the curve that should be used is the low-risk threshold. This baby does not require phototherapy at this time. (Note that if any antibodies are detected prenatally, then a DAT test must always be done regardless of mother’s and baby’s blood types)

All information provided on this website is for educational purposes and does not constitute any medical advice. Please speak to you doctor before changing your diet, activity or medications. 


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