Pathophysiology–Pharmacology (Pathopharm) Practice Exam

A 0.45% sodium chloride solution is categorized as hypotonic because its concentration of solutes is lower than that of the body's cells. When such a solution is administered intravenously, it causes water to move from the bloodstream into the cells, as the cells will have a higher concentration of solutes compared to the surrounding fluid. This movement of water can help hydrate cells and may be used in various clinical situations where cells are dehydrated.

In contrast, isotonic solutions, like 0.9% sodium chloride, have a similar solute concentration to intracellular fluids and do not cause net movement of water into or out of the cells. Hypertonic solutions have a higher concentration of solutes than the cells, leading to water moving out of the cells, which can result in cell shrinkage. Colloids consist of larger molecules, such as proteins, that do not freely cross cell membranes and are used for expanding blood volume rather than addressing cellular dehydration.