What is the effect of administration of large doses of vitamin-K in a newborn?
First, I need to recall the core concept here. Vitamin K is crucial for blood clotting. Newborns are at risk of vitamin K deficiency because their gut flora isn't established yet, which is needed for K synthesis. So, they often get a prophylactic dose at birth.
Now, the question is about administering large doses. The correct answer is likely related to toxicity. But wait, vitamin K toxicity is rare. However, in newborns, high doses could cause hemolysis in those with G6PD deficiency. G6PD deficiency makes red blood cells vulnerable to oxidative stress, and vitamin K might trigger hemolysis in such cases.
So, the core concept is vitamin K's role in coagulation and its potential hemolytic effect in G6PD-deficient infants. The correct answer would be hemolysis in G6PD-deficient newborns. The other options might include things like thrombosis, jaundice, or no effect. But I need to think why each is wrong. For example, thrombosis is unlikely because vitamin K is an anticoagulant in reverse—it's actually used to reverse warfarin. Jaundice could be a distractor but isn't directly caused by vitamin K. No effect is incorrect because there is a documented risk in G6PD deficiency.
The clinical pearl here is that even though vitamin K is given routinely, G6PD status is important. The correct answer is the one mentioning hemolysis in G6PD-deficient infants. The options might be structured around these points. Now, I need to structure the explanation accordingly.
**Core Concept**
Vitamin-K administration in newborns is primarily to prevent vitamin-K deficiency bleeding (VKDB). However, large doses may cause hemolysis in infants with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to oxidative stress on red blood cells.
**Why the Correct Answer is Right**
Vitamin K is a fat-soluble vitamin essential for synthesizing clotting factors II, VII, IX, and X. In G6PD-deficient infants, vitamin K can induce oxidative damage to red blood cells, leading to acute hemolytic anemia. This is because G6PD deficiency impairs the pentose phosphate pathway, reducing glutathione levels and leaving red blood cells vulnerable to oxidative stress from high-dose vitamin K.
**Why Each Wrong Option is Incorrect**
**Option A:** *Thrombosis* – Incorrect. Vitamin K promotes clotting but does not cause thrombosis at prophylactic or therapeutic doses in newborns.
**Option B:** *Jaundice* – Incorrect. While hemolysis can cause jaundice, the primary risk of large vitamin K doses is direct hemolysis, not indirect hyperbilirubinemia.
**Option C:** *No adverse effect* – Incorrect. Large doses are not inert; they pose a hemolytic risk in G6PD-deficient infants.
**Clinical Pearl / High-Yield Fact**
Always screen for G6PD deficiency before administering high-dose vitamin K to newborns. Remember: **