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. The rule of thumb is, “if the gut works, use it.” However, supplemental or total parenteral nutrition is indicated when nutritional requirements cannot be met adequately via oral or enteral feeding or if oral or enteral feeding are contraindicated.
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 However, EN alone is often insufficient in providing the required amount of energy and protein.3 This may result in nutritional deficits known to worsen clinical outcomes.4 In these cases, parenteral nutrition can help to fill the caloric gap.3
Parenteral nutrition (PN) is the intravenous infusion of nutrients directly into the systemic circulation, bypassing the gastrointestinal (GI) tract.5
When EN is Contraindicated
If EN is contraindicated or a limited tolerance for EN over a prolonged period does not allow sufficient intake to cover the patient’s full nutritional needs, PN is indispensable to supplement or replace enteral tube feeding to avoid disease-related malnutrition.6,7
Which Nutrients Are Provided by PN?
PN provides water and essential nutrients such as amino acids, carbohydrates, lipids and micronutrients.
These nutrients are infused in their essential form:
- Carbohydrates: infused as glucose to provide rapidly available energy.
- Amino acids: used by the body as primary constituents of muscle proteins, play a role in biochemical reactions and immune response.
- Lipids: represented by lipid emulsions containing triglycerides; serving as a compact way to store energy because of their high energy and low water content; supply essential fatty acids and constitute an important part of the structure of the cells.
All three macronutrients in the right amounts provide balanced and adequate nutrition support to 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. In fact, PN and EN complement each other, e.g. with the use of PN plus minimal enteral feeding or EN plus supplemental PN.
- 1. 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. 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.
- 4. 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.
- 5. 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.
- 6. 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.
- 7. Austrian Society of Clinical Nutrition (AKE). Recommendations for enteral and parenteral nutrition in adults. Vienna 2008.