Intravenous (IV) fluids are used to treat electrolyte imbalances, replace fluid losses, and treat infection. Fluids will most commonly be packaged in plastic bags, available in sizes ranging from 25 mL to 1,000 mL. For substances that are unstable in plastic bags, glass bottles will be used. Since a glass bottle cannot collapse, there must be a mechanism that allows air to enter the bottle. This is usually accomplished by incorporating a vent into the drip chamber of the tubing.
IV fluids can be categorized as either hypotonic, isotonic or hypertonic solutions. The type of solution administered is often dependent on the serum electrolyte results for a particular patient, and his / her fluid balance.
Hypotonic solutions (less than 250 mEq/L) contain less sodium chloride content than the cells of the body. This causes free water to move out of the vasculature and into the intracellular space through osmosis. Hypotonic solutions are used to treat gastric fluid loss and dehydration from excessive diuresis. Examples include half normal saline or 0.45% sodium chloride (0.45% NS) and one third normal saline or 0.33% sodium chloride (0.33% NS). These solutions do not provide any calories or additional electrolytes.
Isotonic solutions (about 300 nEq/L) have an electrolyte content that is approximately equal to that of the body’s cells. Since the electrolytes are balanced, there is negligible osmolar pressure, and fluids tend to increase intravascular volume. Therefore, this solution is often used to replace extracellular fluid losses. Normal saline (0.9% NS) or 0.9% sodium chloride solution and lactated Ringer’s (LR) solution are examples of isotonic fluids. Isotonic solutions generally do not provide calories or free water.
Hypertonic solutions (375 mEq/L or greater) have an electrolyte content that is greater than the cells of the body. These are the most dangerous as increased osmotic pressure will cause fluid to move into the vascular space. This can result in increased volume of fluids in the vasculature, leading to pulmonary edema, especially for a patient who has renal or cardiac disease. Hypertonic solutions are used to treat patients experiencing severe hyponatremia. Solutions of 10% dextrose in water (D10W) and 5% dextrose in 0.9% sodium chloride (D5NS) are examples of hypertonic fluids. Depending on the type of solute, these solutions may provide calories, free water, and some electrolytes to patients.
Hypertonic solutions may also be extremely irritating to the patient’s veins. Therefore, some must only be infused through a central venous line. Before initiating a hypertonic solution, be sure to check your facility’s policy to determine the appropriate intravenous route.
It is common for vitamins and additional electrolytes to be infused along with an IV solution. To avoid contamination and human errors, most IV fluids are manufactured with the additives already included. However, if an IV solution with the prescribed additives is not available, they should be added in the pharmacy department under a laminar flow hood.
Be aware that the names of IV solutions are often abbreviated or shortened. Therefore, it is important for you to become familiar with each of the different solutions you will be using. If you are uncertain about the nomenclature of contents of the solution you will be administering, consult an intravenous therapy drug guide or a pharmacist before initiating the infusion.
The Centers for Disease Control and Prevention (CDC) allows lipid containing-solutions to hang for no more than 24 hours. Lipid-only emulsions can hang for only 12 hours. Blood and blood products must be replaced after four hours.
Note that there are no specific guidelines for other parenteral infusions. However, for infection-control prevention, most facility policies will not allow any other fluid to hang for more than 24 hours at room temperature, and only if there is no suspicion of contamination. You should be familiar with your facility’s guidelines.