What Is Total Parenteral Nutrition (TPN)? - Definition, Components & Complications

Instructor: Meghan Greenwood

Meghan has taught undergraduate and graduate level science courses and has a PhD in Immunology.

This lesson will describe what total parenteral nutrition is and why it is used. It will also list some of the common components of the formula as well as the complications that are associated with the procedure.

What is Total Parenteral Nutrition?

You just sat down at your favorite restaurant and ordered a chicken salad. The waiter sets it in front of you, and you automatically start to salivate. Mmmm, the first bite is delicious! However, eating is more than just delicious - it is necessary for living. When you eat, the food travels to your stomach where it is broken down into nutrients and waste. The waste continues to move through your digestive tract until it is passed in a bowel movement, whereas the nutrients are absorbed into your bloodstream. This type of nutrition fuels your body's cells, muscles, and organs to behave properly and perform their normal functions for sustaining life. The next time you eat a salad with chicken, think of how the vegetables and chicken are essentially supplying life support, enabling you to walk down the sidewalk or read a book.

What if you had a condition that blocked your ability to eat? Thankfully, healthcare providers can ensure that you get the balanced diet you need via intravenous nutrition. Total parenteral nutrition or TPN is the intravenous delivery of all of your daily nutritional requirements (in contrast, parenteral nutrition provides only some of your nutrition and is usually given as a supplement to normal eating). TPN is basically a liquid food mixture that, when given, bypasses the mouth, stomach, and digestive tract and goes directly into the bloodstream to rapidly reach the tissues and organs. It is typically given to patients who do not have a fully functioning digestive tract, such as those with bowel obstruction, specific stages of ulcerative colitis and Crohn's disease,, cancer patients, and pediatric gastrointestinal disorders.

The digestive system includes the mouth, stomach and intestines. TPN bypasses all of these tissues and directly delivers food to the bloodstream.
Digestive tract

TPN Components

TPN is typically made up of water, proteins, lipids, carbohydrates, electrolytes, and other vitamins and minerals. Proteins and carbohydrates are important for fueling muscles and providing energy, lipids provide fats, and the electrolytes and other elements maintain normal functions of almost every organ in your body while keeping you hydrated. Depending on your age and weight, the amount of each of the components within the TPN mixture will vary. For example, if you are overweight, you will need more carbohydrates in your TPN than a person who is of normal weight; or if your child is undergoing the procedure, he or she may receive less fluid but more protein than you would, to sustain high energy needs. Similarly, if a patient has an underlying kidney or heart problem, certain changes may be made to the mixture to reduce protein content or total fluid. Each TPN bag can be ordered for a patient as a standard, ready-to-use mixture or customized mixture for the individual recipient. Ready-to-use bags should be given to patients who are more stable, whereas customization can help improve the well-being of unstable or heavily restricted patients.

A typical TPN bag contains a mix of lipids (fat), amino acids (protein), and glucose (carbohydrates).
TPN IV bag

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