Phototherapy To Reduce Bilirubin Level In Neonate-Mechanism and Effects

Phototherapy To Reduce Bilirubin Level In Neonate-Mechanism and Effects:

The ancient people knew this effect. Even in the rural area of Pakistan and other countries, the mothers keep their baby in sun for several minutes because they know that this sun energy imparts some beneficial effects on their baby. Now we are going to learn how solar energy helps a neonate.

Every newborn baby has 11 million RBCs per millilitre (normal adult level is 5 million RBCs/mm cube) These RBCs also have a shorter lifespan. After birth, the neonate is exposed to environmental oxygen. So the extra RBCs undergo destruction and within few weeks RBCs level reduces to lower level. The increased destruction of RBCs leads to the excessive formation of bilirubin. Which imparts a yellow colour to the baby's skin which is known as neonatal jaundice. (read this article to have a clear idea about neonatal jaundice - Indirect hyperbilirubinemia in the neonate, causes, signs and symptoms and treatment)

•Clinical jaundice and indirect hyperbilirubinemia are reduced on exposure to high intensity of light in the visible spectrum. Bilirubin absorbs light maximally in the blue range (420–470nm). Nonetheless, broad-spectrum white, blue, special narrow-spectrum (super) blue, and less often, green lights have been effective in reducing bilirubin levels. Bilirubin in the skin absorbs light energy, which by photo-isomerization converts the toxic native unconjugated 4Z,15Z-bilirubin into the unconjugated configurational isomer 4Z,15E-bilirubin. The latter is the product of a reversible reaction and is excreted in bile without any need for conjugation. Phototherapy also converts native bilirubin, by an irreversible reaction, to the structural isomer lumirubin, which is excreted by the kidneys in the unconjugated state. Thus bilirubin level in the blood starts to decrease when a neonate is exposed to the sun. The ancient people knew this effect. Even in the rural area of Pakistan and other countries, the mothers keep their baby in sun for several minutes because they know that this sun energy imparts some beneficial effects on their baby.

Now you all have got the idea about those beneficial effects.

The use of phototherapy has decreased the need for exchange transfusion in term and preterm infants with hemolytic and nonhemolytic jaundice. When indications for exchange transfusion are present, phototherapy should not be used as a substitute. However, phototherapy may reduce the need for repeated exchange transfusions in infants with hemolysis.

Phototherapy is indicated only after the presence of pathologic hyperbilirubinemia has been established. The basic cause or causes of jaundice should be treated concomitantly. Prophylactic phototherapy in VLBW (very low birth weight) infants may prevent hyperbilirubinemia and may reduce the incidence of exchange transfusions. VLBW infants receiving phototherapy for 1–3 days have peak serum bilirubin concentrations about half those of untreated infants. In premature infants without significant hemolysis, serum bilirubin usually declines 1–3 mg/dL after 12–24hr of conventional phototherapy, and peak levels may be decreased by 3–6mg/dL. The therapeutic effect depends on the light energy emitted in the effective range of wavelengths, the distance between the lights and the infant, and the amount of skin exposed, as well as the rate of hemolysis and in vivo metabolism and excretion of bilirubin.
•The available commercial phototherapy units vary considerably in spectral output and the intensity of radiation emitted; therefore, the dose can be accurately measured only at the skin surface.

Does dark skin reduce the efficacy of phototherapy?

The answer is No, Dark skin does not reduce the efficacy of phototherapy.

When should exchange transfusions be given to a neonate with jaundice? Click here
What is the concomitant pharmacological Treatment of neonatal jaundice?