What is a defining feature of isotonic solutions compared to blood plasma?

Isotonic solutions are characterized by having the same concentration of solutes as blood plasma. This is significant because maintaining isotonicity is essential for fluid balance in the body; it helps minimize the movement of water into or out of cells. When isotonic solutions are administered, they do not cause cells to shrink or swell, which can occur if a solution is either hypertonic (higher solute concentration) or hypotonic (lower solute concentration).

This characteristic is crucial in clinical settings, particularly in IV therapy, where isotonic solutions such as 0.9% saline or Lactated Ringer's solution are often used to replace fluids without causing imbalances in cellular hydration. The other choices either refer to concepts that would define hypertonic or hypotonic solutions or mention specific components that do not determine a solution's tonicity relative to plasma.