Which of the following solutions is considered hypotonic?

A hypotonic solution is one that has a lower concentration of solutes compared to the fluid inside the cells. When cells are exposed to a hypotonic solution, water moves into the cells to balance the solute concentration, which can lead to cell swelling or even lysis.

In the context of the answer provided, 0.33% NaCl is considered hypotonic because it contains a lower concentration of sodium chloride compared to the physiological concentration found in body fluids. The normal saline solution, which is 0.9% NaCl, is isotonic and would therefore have no significant effect on cell volume under normal circumstances. The 5% dextrose in normal saline starts as an isotonic solution but becomes hypotonic once the dextrose is metabolized in the body. Ringer's solution is also isotonic, composed of electrolytes that closely mimic plasma.

Understanding the effects of hypotonic solutions is crucial in IV therapy, especially when administering fluids to prevent cellular dehydration or when treating conditions that require precise fluid management.