15.3 Intravenous Solutions
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When clients experience deficient fluid volume, intravenous (IV) fluids are often prescribed. IV fluid restores fluid to the intravascular compartment, and some IV fluids are also used to facilitate the movement of fluid between compartments due to osmosis. There are three types of IV fluids: isotonic, hypotonic, and hypertonic.
Isotonic Solutions
Isotonic solutions are IV fluids that have a similar concentration of dissolved particles as blood. An example of an isotonic IV solution is 0.9% Normal Saline (0.9% NaCl). Because the concentration of the IV fluid is similar to the blood, the fluid stays in the intravascular space and osmosis does not cause fluid movement between compartments. See Figure 15.8[1] for an illustration of isotonic IV solution administration with no osmotic movement of fluid with cells. Isotonic solutions are used for clients with fluid volume deficit (also called hypovolemia) to raise their blood pressure. However, infusion of too much isotonic fluid can cause excessive fluid volume (also referred to as hypervolemia).
Hypotonic Solutions
Hypotonic solutions have a lower concentration of dissolved solutes than blood. An example of a hypotonic IV solution is 0.45% sodium chloride (0.45% NaCl). When hypotonic IV solutions are infused, it results in a decreased concentration of dissolved solutes in the blood as compared to the intracellular space. This imbalance causes osmotic movement of water from the intravascular compartment into the intracellular space. For this reason, hypotonic fluids are used to treat cellular dehydration. See Figure 15.9[2] for an illustration of the osmotic movement of fluid into a cell when a hypotonic IV solution is administered, causing lower concentration of solutes (pink molecules) in the bloodstream compared to within the cell.
However, if too much fluid moves out of the intravascular compartment into cells, cerebral edema can occur. It is also possible to cause worsening hypovolemia and hypotension if too much fluid moves out of the intravascular space and into the cells. Therefore, client status should be monitored carefully when hypotonic solutions are infused.
Hypertonic Solutions
Hypertonic solutions have a higher concentration of dissolved particles than blood. An example of hypertonic IV solution is 3% sodium chloride (3% NaCl). When infused, hypertonic fluids cause an increased concentration of dissolved solutes in the intravascular space compared to the cells. This causes the osmotic movement of water out of the cells and into the intravascular space to dilute the solutes in the blood. See Figure 15.10[3] for an illustration of osmotic movement of fluid out of a cell when hypertonic IV fluid is administered due to a higher concentration of solutes (pink molecules) in the bloodstream compared to the cell.
When administering hypertonic fluids, it is essential to monitor for signs of hypervolemia such as breathing difficultie