## **Core Concept**
The question revolves around the management of a child with severe dehydration due to diarrhea, focusing on the appropriate sodium concentration in the Oral Rehydration Solution (ORS). The child's condition indicates severe dehydration, characterized by a significant loss of fluids and electrolytes.

## **Why the Correct Answer is Right**
The World Health Organization (WHO) and UNICEF recommend a reduced osmolarity ORS for the treatment of diarrhea, which contains 75 mEq/L of sodium. This solution is designed to provide the necessary fluids and electrolytes for rehydration while minimizing stool output and the need for intravenous fluids. For a child weighing 10 kg with severe dehydration, the standard ORS with 75 mEq/L of sodium is appropriate. This concentration helps in correcting dehydration without causing an osmotic imbalance.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 50 mEq/L - This concentration of sodium is lower than the standard recommended by WHO and may not adequately correct the sodium deficit in a severely dehydrated child.
- **Option B:** 90 mEq/L - Although closer to the previously recommended concentration, it is higher than the currently advised 75 mEq/L for reduced osmolarity ORS.
- **Option D:** 120 mEq/L - This is significantly higher than the recommended concentration and could potentially lead to hypernatremia.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the reduced osmolarity ORS with 75 mEq/L of sodium is the current standard for treating dehydration caused by diarrhea in children. The solution's composition is crucial for effective rehydration and minimizing complications.

## **Correct Answer:** . 75 mEq/L