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Section 1 - Types of nutrition support

Routes of nutrition support

The nutritional needs of patients are met through a variety of delivery routes and with an array of nutritional formulation components and administration equipment.

Enteral nutrition (EN)

Long-term nutrition:
  • Gastrostomy
  • Jejunostomy
Short-term nutrition:
  • Nasogastric feeding
  • Nasoduodenal feeding
  • Nasojejunal feeding

Parenteral nutrition (PN)

  • Peripheral Parenteral Nutrition (PPN)
  • Total Parenteral Nutrition (TPN)

Routes of nutritional support

In many patients, either the enteral route, the parenteral route, or a combination of both routes (combination feeding) should be used to meet nutritional needs.


Enteral nutrition

The gastrointestinal tract is always the preferred route of support, i.e., "If the gut works, use it". Most would agree that EN is safer, more cost effective, and more physiologic that PN. Improvements over the past few years have greatly expanded choices in enteral formulas, equipment, and techniques.

Potential benefits of enteral nutrition over PN include:

  1. Physiologic
    • Nutrients are metabolized and utilized more effectively via the enteral than the parenteral route.
    • The gut and liver process enteral nutrients before their release into systemic circulation.
    • The gut and liver help maintain the homeostasis of the amino acid pool as well as the skeletal muscle tissue.
  2. Immunologic
    • Gut integrity is maintained by enteral nutrients through the prevention of bacterial translocation from the gut, sytemic sepsis, and potential increased risk of multiple organ failure.
    • Lack of GI stimulation may promote bacterial translocation from the gut without concurrent enteral nutrition.
    • Provision of early enteral nutrition may minimize risk of gut related sepsis.
  3. Safety (avoid complications related to intravenous access):
    • Catheter sepsis
    • Pneumothorax
    • Catheter embolism
    • Arterial laceration
  4. Cost
    • Cost of EN formula is less than PN.
    • Cost of equipment and personnel for preparation and administration is less.

However, there are contraindications to enteral nutrition support:

  • Expected need less than 5-10 days
  • Severe acute pancreatitis
  • High-output proximal fistulas
  • Inability to gain access
  • Intractable vomitting or diarrhea

Formula selection

Selection of an enteral formula must be patient specific. The functioning and capacity of the GI tract, underlying disease states and patient tolerance must be assessed to determine which formula should be selected. Many formulas are very similar in composition, varying only slightly in nutrient content. It is important to be familar with the properties of commonly used enteral formulas.


Parenteral nutrition

Parenteral nutrition is the provision of nutrients intravenously. It is used in patients who cannot meet their nutritional goals by the oral or enteral route. When the gut is not working, PN is also used for long-term nutrition support in the home setting. The principle forms of PN are peripheral and central (TPN).

PN should only be initiated in patients who are hemodynamically stable and who are able to tolerate the fluid volume, protein, carbohydrate, and lipid doses necessary to provide adequate nutrients.

Conditions warranting cautious use of PN:

  • Azotemia
  • Congestive heart failure
  • Diabetes Mellitus
  • Electrolyte disorders
  • Pulmonary disease

Central PN (TPN) is a concentrated formula which is hyperosmolar and must be delivered into a central vein. TPN provides:

  • Carbohydrates in the form of glucose.
  • Protein in the form of amino acids.
  • Lipids in the form of triglycerides.
  • Electrolytes.
  • Vitamins and trace minerals.

Peripheral PN has similar nutrient components as TPN but in a lower concentration so it may be delivered by peripheral vein. Large fluid volumes must be administered to provide comparable nutrients. PPN is typically used for short periods (up to two weeks) because of limited tolerance.


Combination Feeding

Combination feeding can be used as a bridge between parenteral and enteral (or oral) nutrition in patients whose clinical status does not warrant full enteral nutrition, but whose nutritional status is best managed with some form of enteral nutrition. Thus, patients following a combination feeding regimen receive parenteral and enteral nutrition simultaneously. Even a small amount of enteral nutrition will preserve the entero-hepatic circulation and barrier function of the GI tract.


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Section 1 - Types of nutrition support

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