Enteral Versus Parenteral Nutrition
Differentiating Two Types of Clinical Nutrition Support
The choice of nutrition support and route of administration depends on the patient’s clinical state. It is widely accepted that “if the gut works, use it.” Importantly, supplemental or total parenteral nutrition is indicated when nutritional requirements cannot be met via oral or enteral feeding or if oral or enteral feeding are contraindicated.
Enteral and Parenteral Nutrition Defined
Enteral nutrition (EN) includes oral nutritional supplements (ONS) and enteral tube feeding via nasogastric, nasoenteral or percutaneous tubes.1 EN provides nutrients and energy to the mucosal cells, stimulating epithelial cell metabolism, bile flow and pancreatic secretions as well as the release of enterotrophic gastrointestinal (GI) hormones, and increasing mucosal blood flow.2 Whereas parenteral nutrition (PN) provides nutrients, via an intravenous infusion, directly into the systemic circulation, bypassing the gastrointestinal (GI) tract.
Indications for EN or PN
The Society of Critical Care Medicine (SCCM), the European Society for Clinical Nutrition and Metabolism (ESPEN) and the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) recommend that if there is evidence of protein calorie malnutrition on admission and EN is not feasible, it is appropriate to initiate PN as soon as possible.3
In order to prevent under-nutrition and related adverse effects, all intensive care unit (ICU) patients who are not expected to be on a full oral diet should first receive clinical nutrition, preferably EN within 24 to 48 hours of admission. However, EN alone is often insufficient in providing the required amount of energy and protein.4 This may result in nutritional deficits known to worsen clinical outcomes.5 Patients receiving less than their targeted enteral feeding after two to three days should be considered for supplemental PN to fill the caloric gap.4,6
If EN is contraindicated, PN should be used within 24 to 48 hours.1
To read more about how to determine the correct choice of nutrition support, click here.
What Nutrients Are Provided by PN?
Clinical nutritional therapy provided through PN includes water and essential nutrients such as amino acids, carbohydrates, fats and micronutrients.
These nutrients are infused in their essential form:
- Carbohydrates: Infused as glucose with the goal to provide rapidly available energy.
- Proteins: Present as amino acids that will be used by the body as primary constituents of muscles, as well as playing a role in biochemical reactions and immune response.
- Fats: Represented by lipid emulsions containing triglycerides. They serve as a compact way to store energy because of their high energy and low water content. They also supply essential fatty acids and constitute an important part of the structure of the cells.
All three macronutrients in the right amounts make for balanced and adequate nutrition support that can positively affect clinical outcomes such as infection rates, length of hospital stay or mortality.
Nutritional support is not restricted to the exclusive administration of EN or PN, but PN and EN may complement each other, e.g. with the use of PN plus minimal “trophic” enteral feeding or EN plus supplemental PN.
- 1. a. b. Kreymann KG, Berger MM, Deutz NE et al. ESPEN Guidelines on Enteral Nutrition: Intensive care. Clinical Nutrition 2006;25(2):210–223.
- 2. Druml W. Clinical strategies for prevention of bacterial translocation. In: Herbert MK, editor. Problems of the gastrointestinal tract in anesthesia. Springer Verlag 1999:118-126.
- 3. Gramlich L, Kichian K, Pinilla J et al. Does enteral nutrition compared to parenteral nutrition result in better outcomes in critically ill adult patients? A systematic review of the literature. Nutrition 2004;20:843-848.
- 4. a. b. Heidegger CP, Berger MM, Graf S et al. Optimisation of energy provision with supplemental parenteral nutrition in critically ill patients: a randomised controlled clinical trial. Lancet 2013;381(9864):385-393.
- 5. Thibault R, Heidegger CP, Berger MM et al. Parenteral nutrition in the intensive care unit: cautious use improves outcome. Swiss Med Wkly 2014;144:w13997.
- 6. Singer P, Berger MM, Van den Berghe G et al. ESPEN Guidelines on Parenteral Nutrition: intensive care. Clin Nutr 2009;28(4):387-400.
- 7. National Collaborating Centre for Acute Care (UK). Nutrition Support for Adults Oral Nutrition Support, Enteral Tube Feeding and Parenteral Nutrition. NICE Clinical Guidelines, No. 32 London 2006.
- 8. Rothaermel S, Bischoff SC, Bockenheimer-Lucius G et al. Ethical and legal points of view in parenteral nutrition - guidelines on parenteral nutrition chapter 12. Ger Med Sci 2009;7:Doc16.