Parenteral nutrition (PN) is feeding a person intravenously, bypassing the usual process of eating and digestion. The person receives nutritional formulae that contain nutrients such as glucose, amino acids, lipids and added 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. It may be called peripheral parenteral nutrition (PPN) when administered through vein access in a limb, rather than through a central vein.
- 1 Mechanism
- 2 Indications
- 3 Duration
- 4 Complications
- 5 Solutions
- 6 Emulsifier
- 7 Total parenteral nutrition
- 8 Individual components
- 9 See also
- 10 References
- 11 External links
|This section does not cite any references or sources. (May 2013)|
A mechanical pump under computer control is used to dispense the TPN fluid. Pumps are available that allow TPN administration at home, usually with the preparation and attachment by a family member. These pumps operate on an external dispensing line, part of a single-use dispensing cassette. Connection of the dispensing line to the patient is via a valve on a semi-permanent attached venous port whose closure is displaced by a connection on the dispensing line. Preparation, attachment, and valve replacement require care in sanitation and sterile techniques at specific locations. The use of a rechargeable battery and a portable component pack allows a convenient household mobility for many patients during administration periods, these being typically from twelve to sixteen hours a day.
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.
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, prolonged diarrhea regardless of its cause, high-output fistula, very severe Crohn's disease or ulcerative colitis, and certain pediatric GI disorders including congenital GI anomalies and necrotizing enterocolitis.
Use in cancer
The benefit of TPN to cancer patients is largely debated, and studies to date have generally showed minimal long term benefit. There is no evidence to support the idea that intravenous nutrition 'feeds the cancer, not the patient'.
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.
TPN fully by-passes the GI tract and normal methods of nutrient absorption. Possible complications, which may be significant, are listed below.
TPN requires a chronic IV access for the solution to run through, and the most common complication is infection of this catheter. Infection is a common cause of death in these patients, with a mortality rate of approximately 15% per infection, and death usually results from septic shock.
Chronic IV access leaves a foreign body in the vascular system, and blood clots on this IV line are common. Death can result from pulmonary embolism wherein a clot that starts on the IV line but breaks off and goes into the lungs.
Patients under long-term TPN will typically receive a periodic heparin flush to dissolve such clots before they become dangerous.
Fatty liver and liver failure
Fatty liver is usually a more long term complication of TPN, though over a long enough course it is fairly common. The pathogenesis is due to using linoleic acid (an omega-6 fatty acid component of soybean oil) as a major source of calories. 
Total parenteral nutrition increases the risk of acute cholecystitis due to complete disuse of gastrointestinal tract, which may result in bile stasis in the gallbladder. Other potential hepatobiliary dysfunctions include steatosis, steatohepatitis, cholestasis, and cholelithiasis. Six percent of patients on TPN longer than 3 weeks and 100% of patients on TPN longer than 13 weeks develop biliary sludge. The formation of sludge is the result of stasis due to lack of enteric stimulation and is not due to changes in bile composition. Gallbladder sludge disappears after 4 weeks of normal oral diet. Administration of exogenous cholecystokinin (CCK) or stimulation of endogenous CCK by periodic pulse of large amounts of amino acids have been shown to help prevent sludge formation. These therapies are not routinely recommended. 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. In newborn infants with short bowel syndrome with less than 10% of expected intestinal length, thereby being dependent upon total parenteral nutrition, 5 year survival is approximately 20%.
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%. Catheter-related infections may be minimised by appropriate choice of catheter and insertion technique. 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. Overall, patients receiving TPN have a higher rate of infectious complications. This can be related to hyperglycemia.
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.
Only a limited number of emulsifiers are commonly regarded as safe to use for parenteral administration, of which the most important is lecithin.[medical citation needed] Lecithin can be biodegraded and metabolized, since it is an integral part of biological membranes, making it virtually non-toxic. Other emulsifiers can only be excreted via the kidneys, creating a toxic load. The emulsifier of choice for most fat emulsions used for parenteral nutrition is a highly purified egg lecithin, due to its low toxicity and complete integration with cell membranes. Use of egg-derived emulsifiers is not recommended for people with an egg allergy due to the risk of reaction. 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.
Total parenteral nutrition
Solutions for total parenteral nutrition may be customized to individual patient requirements, or standardized solutions may be used. The use of standardized parenteral nutrition solutions is cost effective and may provide better control of serum electrolytes. Ideally each patient is assessed individually before commencing on parenteral nutrition, and a team consisting of specialised doctors, nurses, clinical pharmacists and Registered Dietitians evaluate the patient's individual data and decide what PN formula to use and at what infusion rate.
For energy only, intravenous sugar solutions with dextrose or glucose are generally used. This is not considered to be parenteral nutrition as it does not prevent malnutrition when used on its own. Standardized solutions may also differ between developers. Following are some examples of what compositions they may have. The solution for normal patients may be given both centrally and peripherally.
|Examples of total parenteral nutrition solutions|
|Substance||Normal patient||High stress||Fluid-restricted|
|Amino acids||85 g||128 g||75 g|
|Dextrose||250 g||350 g||250 g|
|Lipids||100 g||100 g||50 g|
|Na+||150 mEq||155 mEq||80 mEq|
|K+||80 mEq||80 mEq||40 mEq|
|Ca2+||360 mg||360 mg||180 mg|
|Mg2+||240 mg||240 mg||120 mg|
|Acetate||72 mEq||226 mEq||134 mEq|
|Cl-||143 mEq||145 mEq||70 mEq|
|P||310 mg||465 mg||233 mg|
|MVI-12||10 mL||10 mL||10 mL|
|Trace elements||5 mL||5 mL||5 mL|
Individual nutrient components may be added to more precisely adjust the body contents of it. That individual nutrient may, if possible, be infused individually, or it may be injected into a bag of nutrient solution or intravenous fluids (volume expander solution) that is given to the patient.
Administration of individual components may be more hazardous than administration of pre-mixed solutions such as those used in total parenteral nutrition, because the latter are generally already balanced in regard to e.g. osmolarity and ability to infuse peripherally. For example, incorrect IV administration of concentrated potassium can be lethal, but this is not a danger if the potassium is mixed in TPN solution and diluted.
Vitamins may be added to a bulk premixed nutrient immediately before administration, typically in two doses, one fat soluble, the other water soluble, this since the additional vitamins can promote spoilage of stored product.
- Kozier, B., & Erb, G., & Berman, A.J., & Burke, K., & Bouchal, S. R., & Hirst, S. P.. (2004). Fundamentals of Nursing: The Nature of Nursing Practice in Canada. Canadian Edition. Prentice Hall Health: Toronto.
- American Gastroenterological Association medical position statement: parenteral nutrition
- The Merck Manual, 2008
- Heird, WC; Gomez, MR (June 1994). "Total parenteral nutrition in necrotizing enterocolitis.". Clinics in perinatology 21 (2): 389–409. PMID 8070233.
- Deshpande, KS (July 2003). "Total parenteral nutrition and infections associated with use of central venous catheters.". American journal of critical care : an official publication, American Association of Critical-Care Nurses 12 (4): 326–7, 380. PMID 12882062.
- Mollitt, DL; Golladay ES. (August 1983). "Complications of TPN catheter-induced vena caval thrombosis in children less than one year of age". Journal of pediatric surgery 18 (4): 462–7. doi:10.1016/S0022-3468(83)80201-2. PMID 6413671.
- Mailloux, RJ; DeLegge, MH; Kirby, DF (1993 Nov-Dec). "Pulmonary embolism as a complication of long-term total parenteral nutrition". JPEN. Journal of parenteral and enteral nutrition 17 (6): 578–82. doi:10.1177/0148607193017006578. PMID 8301814.
- Evaluation of OMEGAVEN 10%® (n-3 EFA Lipid Emulsion) in Home Parenteral Nutrition-associated Liver Disease (MEGANORM). Retrieved 15 April 2013.
- Piper, SN; Rohm KD (Dec 2009). "Hepatocellular integrity after parenteral nutrition: comparison of a fish-oil-containing lipid emulsion with an olive-soybean oil-based lipid emulsion". Eur J Anaesthesiol. 26 (12): 1076–82. doi:10.1097/EJA.0b013e32832e08e0. PMID 19916246.
- Tucker, RA; Jenkins, HL (1984). "Acalculous cholecystitis and fever related to total parenteral nutrition". Drug intelligence & clinical pharmacy 18 (11): 897–9. PMID 6437783.
- Wang, H; Khaoustov, VI; Krishnan, B; Cai, W; Stoll, B; Burrin, DG; Yoffe, B (October 2006). "Total parenteral nutrition induces liver steatosis and apoptosis in neonatal piglets". The Journal of nutrition 136 (10): 2547–52. PMID 16988124.
- Quigley EM, Marsh MN, Shaffer JL, Markin RS (January 1993). "Hepatobiliary complications of total parenteral nutrition". Gastroenterology 104 (1): 286–301. PMID 8419252.
- Vanderhoof JA, Langnas AN (1997). "Short-bowel syndrome in children and adults". Gastroenterology 113 (5): 1767–78. doi:10.1053/gast.1997.v113.pm9352883. PMID 9352883.
- Spencer AU, Neaga A, West B, et al. (September 2005). "Pediatric short bowel syndrome: redefining predictors of success". Ann. Surg. 242 (3): 403–9; discussion 409–12. doi:10.1097/01.sla.0000179647.24046.03. PMC 1357748. PMID 16135926. (mean follow-up time was 5.1 years)
- 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.
- 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.
- G. Edward Morgan, Jr., Maged S. Mikhail, Michael J. MurrayClinical Anesthesiology, 4th Edition
- McCowen, KC; Friel, C; Sternberg, J; Chan, S; Forse, RA; Burke, PA; Bistrian, BR (2000). "Hypocaloric total parenteral nutrition: effectiveness in prevention of hyperglycemia and infectious complications--a randomized clinical trial". Critical Care Medicine 28 (11): 3606–11. PMID 11098961.
- 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.
- 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.
- Lecithin - An Emulsifier for Parenteral Use: TORVS Research Team
- Lipid Emulsions as Drug Delivery Systems: Jack Stevens, Pam Mims and Neil Coles
- Hayes, EM; Cohen KR, Pinard BE,Lauletta J, Ruggiero R. (2000). "Standardized versusindividually customized parenteral nutrition solutions: a comparison ofserum electrolyte values". P&T 25 (2): 78–80, 83, 87.
- Intravenous Potassium Guidelines (ADULTS) From RNSH Pharmacy Department. Authorised by: Margaret Duguid. Last Modified: June 2006.
- American Society for Parenteral and Enteral Nutrition
- Oley Foundation for people who feed by tube or IV at home
- Calculating Parenteral Feedings at California State University, San Bernardino
- PINNT UK based support group for Patients on Intravenous and Nasogastric Nutrition Therapy
- Nieman, Liesje (Revised January 2008). "Parenteral Nutrition in the NICU". NutritionDimension.com. Retrieved 16 April 2013. "Course ID code: PNN07"