What Are Isotonic Fluids And How Are They Used In IV Therapy For Dehydration?

As intravenous therapies become more popular, you may be wondering how the different IV fluids interact with your body. What are isotonic fluids, and how do they help dehydration? Keep reading for the information you need to determine if dehydration IV therapy is right for you.

Understanding tonicity

Tonicity refers to the volume behavior of cells in a solution. Cells are divided into two parts- intracellular and extracellular. The intracellular part refers to the inside of the cell, and the extracellular part refers to the outside of the cell. Both parts are made up of a solution, which may transfer fluid between them to reach their ideal state. This process is known as osmosis.

IV solutions are given to help body cells achieve their ideal state of tonicity, known as the isotonic state. This means that cells have the same concentration both inside and outside the cell, allowing fluids to flow into and out of the cell simultaneously. Depending on what health concern needs to be addressed, you may be given one of three solutions:

Isotonic fluids

Isotonic solutions are designed to increase extracellular fluid volume. They have the same concentration of electrolytes as blood plasma. Examples of common reasons extracellular fluid volume needs to be increased include blood loss, dehydration, and surgery.

Common isotonic IV solution formulas include:

• 5% Dextrose in 0.225% saline (D5W1/4NS)
• 5% Dextrose in water [(D5W) (Note: This may also function as a hypotonic solution in certain situations)]
• Lactated Ringer’s
• Normal Saline – 0.9% NaCl

Hypotonic fluids

Hypotonic fluids are designed to shift fluids intracellularly, or from the outside of the cell to the inside. Cells themselves need to be rehydrated, which can result in cell swelling. Hypotonic IV solutions have less solutes than blood plasma. Common reasons to administer hypotonic fluids include diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemia.

Common hypotonic IV solution formulas are:

• 0.45% Saline (1/2 NS)
• 0.225% Saline (1/4 NS)
• 0.33% Saline (1/3 NS)

These fluids should be avoided in certain health situations, as inappropriate use could result in depleting the fluids of the circulatory system. People with extensive burns, trauma, or who are at risk of increased cranial pressure should avoid hypotonic IV solutions.

Hypertonic fluids

Hypertonic fluids are designed to transfer fluid from inside the cell to outside, or extracellularly. This results in cell shrinkage. Hypertonic IV solutions have more solutes than blood plasma. These fluids are used very cautiously, typically in Intensive Care Units (ICUs) to address rapidly developing side effects of fluid overload known as pulmonary edema.

Examples of common hypertonic IV solution formulas include:

• 5% Dextrose in Lactated Ringer’s
• 5% Dextrose in 0.45% Saline
• 5% Dextrose in 0.9% Saline
• 10% Dextrose in Water (D10W)
• 3% Saline
• 5% Saline

Other ways IV fluids are classified

There are several other ways IV fluids can help address health concerns.

Nutrient solutions

These IV fluids typically contain ingredients that function as the carbohydrate component of the solution, as well as water. Water helps ensure the body is properly hydrated, while carbohydrates such as dextrose, glucose, and levulose provide calories to help boost energy. These solutions help prevent dehydration as well as ketosis.

Typically, the body burns glucose to create energy. If glucose levels are insufficient, the body will begin to burn fat instead, which can lead to health problems. Nutrient solutions ensure that the body has sufficient glucose to fuel metabolic processes. An example of a nutrient solution is 5% Dextrose in water (D5W).

Electrolyte solutions

Electrolyte IV fluids can vary in the amounts and types of electrolytes they contain to help restore electrolyte balance. Examples of electrolyte solutions include 0.9% saline and Lactated Ringer’s.

Alkalinizing solutions

Alkalinizing solutions are used to treat metabolic acidosis, a condition in which body fluids contain too much acid. Metabolic acidosis can result from your body creating too much acid, difficulty in getting rid of acid, or an inability to balance acids in body fluids. Alkalinizing solutions help balance acid levels in the body while ensuring you are properly hydrated. Lactated Ringer’s solution is also an alkalinizing solution.

Acidifying solutions

Acidifying solutions are administered to combat metabolic alkalosis, a condition in which blood becomes too alkaline, meaning it does not contain enough acids. Metabolic alkalosis occurs when the body produces too much bicarbonate, or too little acid. This can happen as a result of vomiting or dehydration, or due to the body retaining too many alkaline ions. Acidifying solutions help ensure bicarbonate levels in the body are restored. 0.9% saline is an acidifying solution.

Volume expanding solutions

Volume expanding solutions are designed to increase blood volume after significant loss of blood or plasma. They help treat conditions like shock, hemorrhage, sepsis, or severe dehydration by restoring vascular volume. This helps stabilize blood flow and ensures the circulatory system can provide sufficient oxygen to organs. Volume expanders include plasma, human albumin, and dextran.

Recognizing dehydration

Dehydration is what happens to the body when it loses more fluids than have been consumed. Examples of ways the body can lose fluids more rapidly include sweating, vomiting, or diarrhea. Dehydration has many negative impacts on the body, which can become very serious if left untreated. Symptoms of dehydration are as follows:

Mild to moderate dehydration:

• Dry mouth, dry skin, and thirst
• Reduced urination and tear production
• Fatigue and constipation
• Headache, dizziness, and lightheadedness

Severe dehydration

• Excessive thirst
• Low blood pressure
• Rapid heart rate
• Rapid breathing
• Dark urine
• Lack of sweat
• Sunken eyes
• Shriveled skin

If someone is showing symptoms of severe dehydration, you should get them medical attention right away. A person experiencing severe diarrhea or vomiting may not be able to drink fluids, which is one of the many advantages of intravenous rehydration.

Electrolytes and dehydration

Your body having enough water is not the only factor in dehydration. Electrolytes are minerals in the body that have an electric charge. They are essential to various body functions, including:

• Helping the body balance pH levels
• Helping the body balance water levels
• Proper function of the brain, heart, muscles, and nerves
• Moving nutrients into cells
• Moving waste out of cells

Types of dehydration

The electrolyte most involved with dehydration is sodium. Types of dehydration are broken down based on the ratio of salt to fluid.

• Isotonic dehydration occurs when the body loses equal amounts of salt and fluid from the body. The most common cause of isotonic dehydration is diarrhea.
• Hypotonic dehydration occurs when there is too little salt in the body. Some people are more prone to losing electrolytes like sodium when they sweat, putting them at a higher risk of hypotonic dehydration.
• Hypertonic dehydration, also known as hypernatremic dehydration, is an imbalance of salt and fluids in the body, meaning the body loses too much water and keeps too much salt in extracellular fluids. Children are at higher risk of this type of dehydration, which usually requires medical attention.

How are isotonic fluids used in IV therapy for dehydration?

Isotonic fluids are an appropriate solution for most common types of dehydration. They replenish both water and electrolytes to help achieve proper hydration levels. Isotonic IV solutions are packaged in bags. The bag of fluid is hung so that gravity can help the flow of liquid through the long, thin tube to which it is connected. At the end of the tube is a needle which is inserted into a blood vein. This setup allows fluid to be delivered directly to the bloodstream. Dehydration IV therapy sessions typically take 30-60 minutes to complete.

In addition to the benefits of isotonic fluids, you may have the option to add additional vitamins or nutrients that can benefit your health and general wellness. In emergency or hospital situations, it is unlikely that you would be able to request additions to prescribed IV fluids and medications.

However, if you are getting dehydration IV therapy regularly for preventative health or general wellness benefits, your provider may offer a variety of formulas designed to address various health concerns. Formulas can help boost energy, help fight signs of aging, and help you recover faster from workouts. There are also formulas that address other symptoms that often accompany dehydration, such as hangover and stomach flu formulas.

When selecting an isotonic fluid IV provider, you should make sure they are licensed and trained to administer intravenous therapy. Risk of side effects from IV therapy are significantly lessened when administered properly by a trained professional following appropriate hygiene protocols. Your provider should conduct a medical screening to make sure isotonic IV fluids are the right treatment for you.

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