## **Core Concept**
The low osmolar Oral Rehydration Solution (ORS) is a type of solution used to treat dehydration caused by diarrhea. Its composition is crucial for effective rehydration and electrolyte replenishment. The World Health Organization (WHO) and UNICEF have recommended the composition of low osmolar ORS.

## **Why the Correct Answer is Right**
The correct concentration of sodium in low osmolar ORS, as recommended by the WHO and UNICEF, is 75 mmol/L. This reduced osmolarity solution has been shown to be more effective and safer than the original formula, with fewer stool outputs and less vomiting. The sodium concentration in low osmolar ORS is designed to facilitate sodium-glucose cotransport in the intestine, enhancing water absorption.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 50 mmol/L - This is lower than the recommended concentration for low osmolar ORS and might not effectively replenish sodium losses.
- **Option B:** 90 mmol/L - This concentration is higher than recommended for low osmolar ORS and could contribute to hypernatremia or increased osmolarity.
- **Option D:** 110 mmol/L - This is significantly higher than the recommended concentration and would be considered hypertonic, potentially leading to adverse effects.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the low osmolar ORS contains 75 mmol/L of sodium and 75 mmol/L of glucose, which facilitates the absorption of sodium and water in the gut through the sodium-glucose cotransporter. This makes it a critical tool in managing dehydration, especially in pediatric patients.

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