Osmolarity of ReSoMal in mmol/ litre:
The core concept here is understanding the composition of ReSoMal. Osmolarity refers to the concentration of solutes in a solution, which is crucial for osmosis and fluid balance. ReSoMal is used for treating dehydration, especially in cases like diarrhea. The World Health Organization (WHO) has specific guidelines for ORS formulations.
Now, the correct answer is likely 245 mmol/L. I recall that the standard ORS solution has an osmolarity of around 311 mmol/L, but ReSoMal is a modified version with a lower osmolarity. Lower osmolarity solutions are better absorbed in the intestines, reducing the risk of further dehydration. The formula for ReSoMal includes sodium, potassium, chloride, citrate, and glucose. The exact concentrations of these components add up to 245 mmol/L.
Looking at the wrong options, if someone thought it was 311, that's the old ORS value. Another common mistake might be 75, which is way too low. Or maybe 45, which is even lower. Each of these incorrect options would be based on confusion with other solutions or incorrect calculations.
The clinical pearl here is to remember that newer ORS solutions have lower osmolarity for better absorption. The WHO recommends 245 mmol/L for ReSoMal, so that's a key point for exams. Students should note the difference between old and new ORS formulations to avoid confusion.
**Core Concept**
Osmolarity measures the concentration of solute particles in a solution, critical for fluid balance in oral rehydration therapy. ReSoMal (ReSoMal) is a modified oral rehydration solution with lower osmolarity than traditional formulations to enhance intestinal absorption and reduce osmotic diarrhea risk.
**Why the Correct Answer is Right**
ReSoMal has an osmolarity of **245 mmol/L**, calculated by summing ions and glucose: 75 mmol/L Na⁺, 20 mmol/L K⁺, 65 mmol/L Cl⁻, 10 mmol/L citrate, and 75 mmol/L glucose. This low osmolarity (≤250 mmol/L) improves absorption via the sodium-glucose cotransport system (SGLT1) in the small intestine compared to older high-osmolar solutions (311 mmol/L).
**Why Each Wrong Option is Incorrect**
**Option A:** 311 mmol/L refers to the **old WHO ORS** formulation, which caused increased stool output due to high osmolarity.
**Option B:** 75 mmol/L is the **Na⁺ concentration** in ReSoMal, not total osmolarity.
**Option C:** 45 mmol/L is the **K⁺ concentration** in some ORS variants, not ReSoMal’s total osmolarity.
**Clinical Pearl / High-Yield Fact**
Never confuse ReSoMal (245 mmol/L) with older ORS (311 mmol/L).