The paediatrician had been advised phototherapy for the newborn with jaundice. Phototherapy is advised becaus… - RML Lucknow - 2021

RML Lucknow - 2021

Child Health Nursing (Pediatrics)

Easy

Appeared in: RML Lucknow - 2021

Explanation

Phototherapy works by using light energy to change the structure of bilirubin in the skin.
The primary mechanism is structural isomerization, which irreversibly converts toxic, unconjugated bilirubin into a water-soluble isomer called lumirubin.
Lumirubin is non-toxic and can be excreted directly in the urine and bile, bypassing the need for conjugation in the immature newborn liver.
This process is the most effective and rapid way that phototherapy lowers the total serum bilirubin (TSB) level.

Option A: Phototherapy has no direct effect on the newborn's immune system. Its purpose is solely to treat hyperbilirubinemia.
Option C: This describes the normal physiological process of bilirubin conjugation that occurs within the liver, mediated by the enzyme UDP-glucuronyl transferase. Phototherapy is used precisely because this liver pathway is immature in newborns and cannot handle the bilirubin load.
Option D: This statement is too vague. While a minor part of phototherapy involves photo-oxidation (a form of breakdown), the principal and most effective mechanism is the structural isomerization of bilirubin to lumirubin, not just general 'breakdown'.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanism of action of phototherapy in neonatal hyperbilirubinemia as background academic context rather than a clinical decision trigger.
Understanding the mechanism of phototherapy is crucial for nurses to educate parents and manage care effectively.
Nurses must ensure maximal skin exposure, protect the infant's eyes, monitor temperature, and maintain hydration to maximize efficacy and prevent complications.
A key safety measure is monitoring for side effects like skin rashes, loose stools, and dehydration.

How to Approach the Question

First, identify the core subject of the question, which is the mechanism of action for phototherapy in treating neonatal jaundice.
Recall the pathophysiology of neonatal jaundice (excess unconjugated bilirubin due to an immature liver) and how phototherapy intervenes.
Evaluate each option based on this knowledge.
Option A (immunity) is unrelated. Option C describes the liver's natural process, which phototherapy bypasses.
Compare Option B and D. Option B ('change bilirubin to lumirubin') describes the specific, primary chemical change. Option D ('helps in breakdown') is vague and describes a minor secondary process.
Select the most precise and accurate description of the primary mechanism, which is the conversion to lumirubin.

Concept Tested & Keywords

Concept Tested: Mechanism of action of phototherapy in neonatal hyperbilirubinemia.
Stem keywords: phototherapy, newborn, jaundice
Lead-in keywords: because

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