Parenteral nutrition (PN), or intravenous feeding, is the feeding of nutritional products to a person intravenously, bypassing the usual process of eating and digestion. The products are made by pharmaceutical compounding entities or standard pharmaceutical companies. The person receives a nutritional mix according to a formula including glucose, salts, amino acids, lipids, vitamins, and dietary minerals. It is called total parenteral nutrition (TPN) or total nutrient admixture (TNA) when no significant nutrition is obtained by other routes, and partial parenteral nutrition (PPN) when nutrition is also partially enteric. It is called peripheral parenteral nutrition (PPN) when administered through vein access in a limb rather than through a central vein as in central venous nutrition (CVN).
Medical uses 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. It has been used for comatose patients, although enteral feeding is usually preferable, and less prone to complications. Parenteral nutrition is used to prevent malnutrition in patients who are unable to obtain adequate nutrients by oral or enteral routes. The Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition recommends waiting until the seventh day of hospital care to administer parenteral nutrition.
Absolute indications for TPN Diseases that would require the use of TPN include:
Short bowel syndrome Small bowel obstruction Active gastrointestinal bleeding Pseudo-obstruction with complete intolerance to food High-output (defined as > 500ml/day) enteric-cutaneous fistulas (unless a feeding tube can be passed distal to the fistula) Premature birth (unable to take oral feeds)
Gastrointestinal disorders TPN may be the only feasible option for providing nutrition to patients who do not have a functioning gastrointestinal tract or who have disorders requiring complete bowel rest, including bowel obstruction, short bowel syndrome, gastroschisis, gastroparesis, prolonged diarrhea regardless of its cause, very severe Crohn's disease or ulcerative colitis, and certain pediatric GI disorders including congenital GI anomalies and necrotizing enterocolitis.
In the geriatric population 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. Geriatric patients are more inclined to have delayed muscle restoration compared to the younger population. Additionally, older patients are observed to have greater cardiac and renal impairment, insulin resistance, and to have deficiencies in vitamins and crucial elements. Patients who require nutrition therapy but have contraindications for or cannot tolerate enteral nutrition are appropriate candidates for parenteral nutrition. In the geriatric population, it is indicated if oral or enteral nutrition is impossible for 3 days or when oral or enteral nutrition is likely insufficient for more than 7 to 10 days. While there are no complications of parenteral nutrition specific to the geriatric population, complications are more prevalent in this population due to increased comorbidities.
In cancer Patients who are diagnosed with cancer, whether as outpatient undergoing treatment or hospitalized, are at a greater risk of malnutrition and cachexia. Cancer-related malnutrition can be attributed to the decrease in food intake, increase in the need for energy, and the alteration of metabolism. Patients should be assessed early on in their cancer treatment for any nutritional risk, such as by taking routine weights and BMI. Parenteral nutrition is indicated in cancer patients when it is not possible to access the digestive tract or if the tract is ineffective. In advanced cancer patients, the use of PN should be discussed in context of the risks and benefits, such as if the approximate survival rate is longer than 3 months and if PN would be expected to greatly improve the patients' quality of life. It is uncertain whether home parenteral nutrition improves survival or quality of life in people with malignant bowel obstruction.
Duration 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. PN has extended the life of children born with nonexistent or severely deformed organs.
Living with TPN Approximately 40,000 people use TPN at home in the United States, and because TPN requires 10–16 hours to be administered, daily life can be affected. Although daily lifestyle can be changed, most patients agree that these changes are better than staying at the hospital. Many different types of pumps exist to limit the time the patient is "hooked up". Usually a backpack pump is used, allowing for mobility. The time required to be connected to the IV is dependent on the situation of each patient; some require once a day, or five days a week. It is important for patients to avoid as much TPN-related change as possible in their lifestyles. This allows for the best possible mental health situation; constantly being held down can lead to resentment and depression. Physical activity is also highly encouraged, but patients must avoid contact sports (equipment damage) and swimming (infection). 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.
Complications TPN fully bypasses the GI tract and normal methods of nutrient absorption. Possible complications, which may be significant, are listed below. Other than those listed below, common complications of TPN include hypophosphatemia, hypokalemia, hyperglycemia, hypercapnia, decreased copper and zinc levels, elevated prothrombin time (if associated with liver injury), hyperchloremic metabolic acidosis and decreased gastrointestinal motility.
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