[2][3] The person receives a nutritional mix according to a formula including glucose, salts, amino acids, lipids and vitamins and dietary minerals.

[5] Total parenteral nutrition (TPN) is provided when the gastrointestinal tract is nonfunctional because of an interruption in its continuity (it is blocked, or has a leak – a fistula) or because its absorptive capacity is impaired.

Parenteral nutrition is used to prevent malnutrition in patients who are unable to obtain adequate nutrients by oral or enteral routes.

[10] There are physical, physiological, or mental differences in the geriatric population that could potentially lead to poor nutrient intake that would require them to have nutrition therapy.

Additionally, older patients are observed to have greater cardiac and renal impairment, insulin resistance, and to have deficiencies in vitamins and crucial elements.

[13] It is uncertain whether home parenteral nutrition improves survival or quality of life in people with malignant bowel obstruction.

[14] Short-term PN may be used if a person's digestive system has shut down (for instance by peritonitis), and they are at a low enough weight to cause concerns about nutrition during an extended hospital stay.

Long-term PN is occasionally used to treat people suffering the extended consequences of an accident, surgery, or digestive disorder.

Many teens find it difficult to live with TPN due to issues regarding body image and not being able to participate in activities and events.

[19] Death can result from pulmonary embolism wherein a clot that starts on the IV line breaks off and travels to the lungs, blocking blood flow.

The brain uses signals from the mouth (taste and smell), the stomach and gastrointestinal tract (fullness) and blood (nutrient levels) to determine conscious feelings of hunger.

[25] In cases of TPN, the taste, smell and physical fullness requirements are not met, and so the patient experiences hunger, although the body is being fully nourished.

[26] Total parenteral nutrition increases the risk of acute cholecystitis[27] due to complete disuse of the gastrointestinal tract, which may result in bile stasis in the gallbladder.

[30] Such complications are suggested to be the main reason for mortality in people requiring long-term total parenteral nutrition, such as in short bowel syndrome.

[31] In newborn infants with short bowel syndrome with less than 10% of expected intestinal length, thereby being dependent upon total parenteral nutrition, five-year survival is approximately 20%.

Because all of the fetus' nourishment comes from the mother's blood stream, the doctor must properly calculate the dosage of nutrients to meet both recipients’ needs and have them in usable forms.

Incorrect dosage can lead to many adverse, hard-to-guess effects, such as death, and varying degrees of deformation or other developmental problems.

Prepared solutions generally consist of water and electrolytes; glucose, amino acids, and lipids; essential vitamins, minerals and trace elements are added or given separately.

Studies have shown differences in physical and chemical stabilities of these total parenteral nutrition solutions,[47][48][49] which greatly influences pharmaceutical manufacturing of these admixtures.

[medical citation needed] Lecithin can be biodegraded and metabolized, since it is an integral part of biological membranes, making it virtually non-toxic.

The emulsifier of choice for most fat emulsions used for parenteral nutrition is a highly purified egg lecithin,[50] due to its low toxicity and complete integration with cell membranes.

In situations where there is no suitable emulsifying agent for a person at risk of developing essential fatty acid deficiency, cooking oils may be spread upon large portions of available skin for supplementation by transdermal absorption.

[52] Developed in the 1960s by Dr. Stanley Dudrick, who as a surgical resident in the University of Pennsylvania, working in the basic science laboratory of Dr. Jonathan Rhoads, was the first to successfully nourish initially Beagle puppies and subsequently newborn babies with catastrophic gastrointestinal malignancies.

[54] In 2019 the UK experienced a severe shortage of TPN bags due to safety restrictions at the sole manufacturing site, operated by Calea.