Which intravenous fluid is classified as an isotonic solution?

Choice A reason: Dextrose 2.5% in water is a hypotonic solution once the dextrose is metabolized. Hypotonic fluids cause water to shift into cells, which can lead to cellular swelling. This fluid is not isotonic and is therefore incorrect. Choice B reason: 0.45% sodium chloride, also known as half-normal saline, is a hypotonic solution. It provides free water and promotes fluid movement into cells, making it inappropriate to classify as isotonic. Choice C reason: 0.9% sodium chloride, also called normal saline, has an osmolality similar to that of plasma. It does not cause significant fluid shifts between compartments and is classified as an isotonic solution. It is commonly used for fluid resuscitation and maintenance of intravascular volume. Choice D reason: Dextrose 10% in water is a hypertonic solution. It draws water out of cells into the intravascular space and increases serum osmolality. Because of this effect, it is not isotonic and is an incorrect choice.