A patient is admitted to the emergency room with severe dehydration. To rapidly restore blood volume, an intravenous (IV) solution is administered. Which of the following types of solutions would be most effective in increasing the patient's intracellular fluid volume?
- AHypertonic solution
- BColloid solution
- CIsotonic solution
- DHypotonic solution
Show answer & explanationAnswer & explanation
Correct answer: D. Hypotonic solution
To increase intracellular fluid volume, water needs to move from the extracellular space into the cells. This occurs when the extracellular fluid is hypotonic relative to the intracellular fluid. A hypotonic solution has a lower solute concentration than the cells, causing water to move by osmosis into the cells, increasing their volume. While the primary goal in severe dehydration is often to restore overall blood volume with isotonic solutions, specifically increasing *intracellular* fluid requires a hypotonic solution.
Why the other options are wrong
- A. A hypertonic solution has a higher solute concentration than the cells; it would draw water out of the cells, decreasing intracellular fluid volume.
- B. A colloid solution (e.g., albumin) increases plasma volume by increasing oncotic pressure, keeping fluid in the vascular space, but it does not primarily shift fluid into cells to increase intracellular volume.
- C. An isotonic solution has the same solute concentration as the cells; it would expand the extracellular fluid volume but would not cause a net shift of water into the cells to increase intracellular volume.
Hypotonic Solution
A solution with a lower solute concentration than the intracellular fluid, causing water to move into cells by osmosis, leading to cell swelling.
- Lower solute concentration.
- Water moves into cells.
- Increases intracellular fluid volume.
- Can cause cell lysis if severe.
Memory trick: Hypo-Go: 'H'ypotonic makes cells 'H'uge; 'H'yper makes cells 'H'ard.