Updated August 30, 2021
Food provides the nutrition you need to grow, develop, and sustain life.
When you’re healthy, you can eat food through the mouth, which is then chewed, swallowed, and digested — supplying your body with the necessary nutrition.
But if you can’t take food by mouth or your digestive system isn’t functioning properly, you must receive your nutrients intravenously — or through the veins.
Nutrition provided through the veins is known as parenteral nutrition, often called total parenteral nutrition (TPN).
This article explains everything you need to know about parenteral nutrition, including what it is, why it’s needed, and its potential complications.
What is parenteral nutrition?
Parenteral nutrition supplies all or some of your daily nutrition needs through a vein, or intravenously.
It contains a mixture of lipids or fats, dextrose for carbohydrates, amino acids for protein, vitamins, minerals, and electrolytes.
Normally, your digestive system breaks down and absorbs nutrients from the food you eat. These nutrients are then carried by the blood to all parts of your body.
Parenteral nutrition bypasses your body’s digestive system and supplies nutrients directly through a tube called a catheter, which is placed within a large vein, usually the vena cava of the heart.
Parenteral nutrition is typically used for a short time and then discontinued once a person can eat normally. But it can provide adequate nutrition for as long as it’s needed.
People of all ages can receive parenteral nutrition — from infants to older adults.
Parenteral nutrition vs enteral nutrition
Parenteral and enteral nutrition are the same in that they provide your body with nutrition when you can’t meet your needs by mouth.
Where they differ though, is the route in which they supply the nutrients.
Enteral nutrition — commonly known as tube feeding — uses your digestive tract to supply nutrients, whereas parenteral nutrition uses your blood.
With enteral nutrition, a tube may be inserted in your nose and down to your stomach or small intestine.
In other instances, a tube may be surgically placed through your abdomen and into your stomach.
Enteral nutrition can be used if your digestive system is functioning properly.
If it’s not functioning properly, parenteral nutrition must be used to provide your body with nutrition.
Generally, enteral nutrition is preferred when possible because it’s less expensive and carries fewer risks for complications compared with parenteral nutrition (1).
When is parenteral nutrition needed?
There are several instances when you may need parenteral nutrition to provide nutrition that you otherwise couldn’t receive by mouth or with enteral nutrition.
Parenteral nutrition may be needed for (2):
- poor nutrient absorption
- prolonged bowel rest, usually longer than five days
- bowel obstruction, such as intestinal cancer
- severe cases of malnutrition or unintended weight loss
- gastrointestinal (GI) fistula — an abnormal opening in the digestive tract
- an interolance to enteral nutrition due to severe diarrhea or vomitting
Just as there are several instances when a person may need parenteral nutrition, there are also times when it should be avoided.
Parenteral nutrition should be avoided when (2):
- the digestive system is functioning
- nutrition needs can be met with oral or enteral nutrition within five days
- it does not align with a patient’s wishes or end-of-life medical prognoses like advanced dementia
Parenteral nutrition complications
With any invasive medical procedure comes risks, and parenteral nutrition is no exception.
Infection — occurring around the catheter access point to the vein — is the most significant complication of parenteral nutrition.
An infection in your bloodstream, known as sepsis, is very dangerous and can be fatal.
Other potential complications of parenteral nutrition include:
- blood clots
- fluid and electrolyte imbalances
- liver problems
- high blood sugar
- refeeding syndrome
Therefore, to prevent or treat these complications, the interdisciplinary team — consisting of the physician, dietitian, pharmacist, and nurse — should carefully manage your parenteral nutrition.
The bottom line
Parenteral nutrition supplies nutrition through your vein, or intravenously.
It’s often the only feasible option for providing your body with nutrition if you don’t have a functioning GI tract, need bowel rest, or can’t meet your nutritional needs orally or with enteral nutrition.
There are many complications associated with parenteral nutrition, but these can be avoided with the ongoing support of the interdisciplinary team who are trained in nutrition support, like registered dietitians.