2-7

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2-7. NATURE OF SOLUTIONS

There are three movement directions possible following the introduction of injectable solutions into the body. These movement directions are governed by the nature of the solution with regard to body fluids. The fluids are called hypotonic, hypertonic, and isotonic.

a. Hypotonic Solutions. A hypotonic solution is one that has less tonicity than the fluid within the body's cells. This type of fluid is absorbed into the body's cells by moving across the cell's membrane and into the cell. If too much hypotonic solution is added, there is always the danger that the cells could burst or at least become irritated. Examples of hypotonic solutions are 0.45 percent sodium chloride solution and sterile water. This movement is shown in figure 2-4.

b. Hypertonic Solutions. A hypertonic solution is one that has greater tonicity than the fluid within the body's cells. When this type of fluid is injected, it causes the cells to lose fluid into the surrounding spaces. If too much hypertonic solution is injected, the cells will shrink and shrivel. The cells become irritated, and this will probably cause pain at the site of administration. Examples of hypertonic solutions are hyperalimentation solutions and 10 percent dextrose solution. This movement is shown in figure 2-5.

c. Isotonic Solutions. An isotonic solution has the same tonicity as that of body fluids. When this type of fluid is injected, fluids travel equally in both directions. Injection of an isotonic fluid causes no cell irritation to occur. Examples of isotonic fluids are 0.9 percent sodium chloride solution and lactated Ringer's solution. This movement is shown in figure 2-6.

Figure 2-6. Isotonic Solution

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