Which of the following is an example of an isotonic IV fluid?

Isotonic IV fluids are solutions that have an osmolarity similar to that of blood plasma, allowing them to maintain fluid balance without shifting fluid into or out of the cells. Normal saline, which is a 0.9% sodium chloride solution, is a classic example of an isotonic fluid. It is used for hydration and to help maintain electrolyte balance in patients, making it effective for various medical situations, such as fluid resuscitation and dilution of medications.

The reason normal saline is isotonic is that its osmolarity is approximately equal to that of plasma, preventing cellular swelling or shrinkage when administered. It helps to expand the extracellular fluid volume, which is crucial for patients who need fluid replenishment.

Other fluids listed have different osmolarities. Half normal saline is hypotonic and can cause cells to swell as water moves into them, and 3% saline is hypertonic, drawing water out of cells and into the bloodstream, which can lead to cellular dehydration. Dextrose 10% in water is also considered hypertonic once metabolized, as it can lead to an increased osmolarity in the serum. Therefore, normal saline stands out as the only isotonic fluid among the options provided.