Routes of Administration
Parenteral nutrition most often involves the sterile preparation and placement of an intravenous catheter into high-flow blood vessels (intravascular access) for the purposes of delivering the full nutritional needs of the patient. These catheters may be intended for short-term use (e.g., 7 to 10 days) or long-term use (months to years) for selected patients. The final formulation is made by the Pharmacy as an admixture of multiple commercial ingredients under strict sterile conditions and in conformance with the standards set forth by the United States Pharmacopeia under Chapter <797> entitled "Pharmaceutical Compounding - Sterile Preparations"
www.usp.org. The intravenous infusion contains the three basic macronutrients: 1) protein, in the form of crystalline amino acids; 2) carbohydrate as glucose; and, 3) fat as an emulsion of oil-in-water. In addition, the final admixture also contains common electrolytes (e.g., sodium, potassium, calcium, magnesium, phosphorus), trace minerals (e.g., copper, chromium, manganese, selenium, zinc), and multivitamins (e.g., fat-soluble: Vitamins A, D, E, K; and water soluble: e.g., B-vitamins, Vitamin C, folic acid). These specially-prepared formulations are made under the order of a physician prescription and conform with national and international standards for safe parenteral nutrition therapy.
www.espen.org Parenteral nutrition is the most invasive form of nutrition support, thus engendering high clinical risks, and requires expert medical oversight.
Enteral nutrition most often involves the placement of a catheter into the stomach or intestine via the nose or surgically via the abdomen (extravascular access) for the purposes of delivering the full nutritional needs of the patient. As with intravenous catheters, these catheters may also be intended for short-term use (e.g., 7 to 10 days) or long-term use (months to years) for selected patients. The final formulation is most often pre-made from a manufacturer (rather than by the Pharmacy) as complete formulas in a liquid, or powder that is mixed with water just before use. The three basic macronutrients are less chemically refined when compared to parenteral nutrition and often exist as complete 1) proteins from, for example, milk or soy; 2) carbohydrate as, for example, starch; and, 3) fat that can be, for example, from vegetable or fish or even in various mixtures of different oils. The final commercial product is a water-based dispersion of oil-in-water. These formulations are designed to conform with national and international standards for parenteral nutrition.