An isotonic solution is made up of two or more substances and has the same concentration as the blood or cells in the body. An isotonic solution has a solvent inside as well as a solute. Isotonic solutions also have the same salt concentrations as the blood cells that surround them.
In an isotonic solution, cells won't gain or lose water. Saline solution, for example, is made with 0.9 percent NaCl and is isotonic with blood. For patients who are suffering from dehydration, this can be used to help hydrate them. It may also be used if they are unable to take in foods or drinks.
The tonicity or concentration of solutions is important to those in the medical field, because the tonicity of a solution directly affects the body's living cells. If in a higher concentration solution, cells will actually burst to allow water to move into a solution with a lower concentration.
If a living cell is moved into a solution with a lower concentration, also known as a hypertonic solution, then the cell shrinks as the water molecule leaves the cell. This can result in death. For instance, the ocean is a hypertonic solution and can result in a person's severe hydration, according to Innovateus.net.