Which statement about IV solutions is correct?

• A. Hypertonic solutions have osmolality similar to body fluids.
• B. Hypotonic solutions have osmolality higher than body fluids.
• C. Isotonic solutions have osmolality similar to body fluids.
• D. Hypertonic solutions have no effect on cell size.

Answer: (C)

Osmolality and water movement across cell membranes determine how IV fluids affect cell size. Isotonic solutions have osmolality similar to extracellular fluid (body fluids), so there’s no net water shift in or out of cells when these fluids are given; the cells stay about the same size. Hypertonic solutions have a higher osmolality than body fluids, which draws water out of cells into the extracellular space, causing cells to shrink. Hypotonic solutions have a lower osmolality, so water moves into cells and they can swell. Therefore, the statement that isotonic solutions have osmolality similar to body fluids is correct because it explains why they don’t change cell size, while the other options describe conditions that do alter cell size.