Which IV solution is isotonic?

Rationale: A. 3% sodium chloride is hypertonic. It has a higher concentration of solutes than blood plasma and draws water out of cells into the bloodstream. It is used cautiously to treat severe hyponatremia and must be administered slowly under strict monitoring. B. 0.9% sodium chloride (normal saline) is correct. This solution is isotonic, meaning its solute concentration is similar to that of blood plasma. It expands the extracellular fluid volume without causing significant fluid shifts between compartments, making it suitable for fluid resuscitation, maintenance, and medication administration. C. DSW (5% dextrose in water) is initially isotonic in the bag, but once dextrose is metabolized in the body, it becomes effectively hypotonic, as water remains in the extracellular and intracellular spaces. It is used for hydration and as a source of calories, not primarily for expanding extracellular volume. D. 0.45% sodium chloride is hypotonic, with lower solute concentration than plasma. It causes water to move into cells, making it useful for cellular dehydration, but it is not isotonic.