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Parenteral nutrition (PN) is feeding a person intravenously, bypassing the usual process of eating and digestion. The person receives nutritional formulas containing salts, glucose, amino acids, lipids and added vitamins. It is called total parenteral nutrition (TPN) when no food is given by other routes.


General usage

Parenteral nutrition is provided when the gastrointestinal tract is nonfunctional because of an interruption in its continuity or because its absorptive capacity is impaired (Kozier et al., 2004). It has been used for comatose patients, although enteral feeding is usually preferable, and less prone to complications. Indications: TPN may be the only feasible option for patients who do not have a functioning GI tract or who have disorders requiring complete bowel rest, such as the following: Some stages of Crohn's disease or ulcerative colitis, bowel obstruction, certain pediatric GI disorders, e.g., congenital GI anomalies, prolonged diarrhea regardless of its cause, or short bowel syndrome due to surgery (The Merck Manual, 2008).

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. People have survived on total parenteral nutrition for more than 35 years, living fully productive lives.

The preferred method of delivering PN is with a medical infusion pump. A sterile bag of nutrient solution, between 500 mL and 4 L, is provided. The pump infuses a small amount (0.1 to 10 mL/hr) continuously in order to keep the vein open. Feeding schedules vary, but one common regimen ramps up the nutrition over one hour, levels off the rate for a few hours, and then ramps it down over a final hour, in order to simulate a normal metabolic response resembling meal time. This should be done over 12 to 24 hours rather than intermittently during the day.

Chronic PN is performed through a central intravenous catheter, usually through the subclavian or jugular vein with the tip of the catheter at the superior vena cava without entering the right atrium. Another common practice is to use a PICC line, which originates in the arm, and extends to one of the central veins, such as the subclavian with the tip in the superior vena cava. In infants, sometimes the umbilical vein is used.

Battery-powered ambulatory infusion pumps can be used with chronic PN patients. Usually the pump and a small (100 ml) bag of nutrient (to keep the vein open) are carried in a small bag around the waist or on the shoulder. Outpatient TPN practices are still being refined but have been used for years. Patients can receive the majority of their infusions while they sleep and instill heparin in their catheters when they are done to simulate a more "normal" life style off the pump.

Aside from their dependence on a pump, chronic PN patients can live quite normal lives. A non-profit organization, the Oley Foundation, provides free information and programs to better the quality of life for PN and tube fed patients.

In most US hospitals, clinical pharmacists evaluate the patient's individual data and decide what PN formula to use.


Micrograph of periportal fatty liver as may arise due to TPN. Trichrome stain.

The most common complication of PN use is bacterial infection, usually due to the increased infection risk from having an indwelling central venous catheter. In patients with frequent bacterial infections, fungal infections can also occur. Liver failure, often related to fatty liver, may sometimes occur. This condition is generally due to excess in glucose provided in PN solutions.

A recent small-scale study at Children's Hospital Boston on the cause of liver failure suggests it may be due to a large difference in omega-6 to omega-3 ratio. When treated with Omegaven, a different fatty acid infusion (which is approved for limited use in the U.S.), two patients were able to recover from their condition.[1]

Two related complications of PN are venous thrombosis and rarely priapism. Fat infusion during PN is assumed to contribute to both.[2]

Total parenteral nutrition increases the risk of acute cholecystitis due to complete unusage of gastrointestinal tract, which may result in bile stasis in the gallbladder.

In critical and/or perioperative care

Parenteral nutrition is indicated to prevent the adverse effects of malnutrition in patients who are unable to obtain adequate nutrients by oral or enteral routes. Other indications are short gut syndrome, high-output fistula, prolonged ileus, or bowel obstruction. However, the decision to initiate PN needs to be made on an individual patient basis, as different patients will have differing abilities to tolerate starvation.[3]

The nutrient solution consists of water and electrolytes; glucose, amino acids, and lipids; essential vitamins, minerals and trace elements are added or given separately. Previously lipid emulsions were given separately but it is becoming more common for a "three-in-one" solution of glucose, proteins, and lipids to be administered.[4][5]

Complications are either related to catheter insertion, or metabolic, including refeeding syndrome. Catheter complications include pneumothorax, accidental arterial puncture, and catheter-related sepsis. The complication rate at the time of insertion should be less than 5%.[6] Catheter-related infections may be minimised by appropriate choice of catheter and insertion technique.[7] Metabolic complications include the refeeding syndrome characterised by hypokalemia, hypophosphatemia and hypomagnesemia. Hyperglycemia is common at the start of therapy, but can be treated with insulin added to the TPN solution. Hypoglycaemia is likely to occur with abrupt cessation of TPN. Liver dysfunction can be limited to a reversible cholestatic jaundice and to fatty infiltration (demonstrated by elevated transaminases). Severe hepatic dysfunction is a rare complication.[8] Overall, patients receiving TPN have a higher rate of infectious complications. This can be related to hyperglycemia.[9]

See also


  1. ^ Gura KM, Duggan CP, Collier SB, et al. (July 2006). "Reversal of parenteral nutrition-associated liver disease in two infants with short bowel syndrome using parenteral fish oil: implications for future management". Pediatrics 118 (1): e197–201. doi:10.1542/peds.2005-2662. PMID 16818533.  
  2. ^ Hébuterne X, Frere AM, Bayle J, Rampal P (1992). "Priapism in a patient treated with total parenteral nutrition". JPEN J Parenter Enteral Nutr 16 (2): 171–4. doi:10.1177/0148607192016002171. PMID 1556816.  
  3. ^ American Gastroenterological Association medical position statement: parenteral nutrition
  4. ^ Didier ME, Fischer S, Maki DG (1998). "Total nutrient admixtures appear safer than lipid emulsion alone as regards microbial contamination: growth properties of microbial pathogens at room temperature". JPEN J Parenter Enteral Nutr 22 (5): 291–6. doi:10.1177/0148607198022005291. PMID 9739032.  
  5. ^ Rollins CJ, Elsberry VA, Pollack KA, Pollack PF, Udall JN (1990). "Three-in-one parenteral nutrition: a safe and economical method of nutritional support for infants". JPEN J Parenter Enteral Nutr 14 (3): 290–4. doi:10.1177/0148607190014003290. PMID 2112645.  
  6. ^ McGee DC, Gould MK (March 2003). "Preventing complications of central venous catheterization". N. Engl. J. Med. 348 (12): 1123–33. doi:10.1056/NEJMra011883. PMID 12646670.  
  7. ^ Horattas MC, Trupiano J, Hopkins S, Pasini D, Martino C, Murty A (February 2001). "Changing concepts in long-term central venous access: catheter selection and cost savings". Am J Infect Control 29 (1): 32–40. doi:10.1067/mic.2001.111536. PMID 11172316.  
  8. ^ G. Edward Morgan, Jr., Maged S. Mikhail, Michael J. MurrayClinical Anesthesiology, 4th Edition
  9. ^ McCowen K, Friel C, Sternberg J et al. Hypocaloric total parenteral nutrition: effectiveness in prevention of hyperglycemia and infectious complications--a randomised clinical trial. Crit Care Med 2000; 28: 3606-11

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