Introduction to Parenteral Nutrition (PN)

Malnutrition is associated with increased morbidity, mortality and treatment costs1-4

Malnutrition has repeatedly been shown to be detrimental to recovery from disease, trauma and surgery.1 Higher treatment costs in malnourished patients have also been demonstrated.2 In critically ill patients, malnutrition results in an increased number of ventilator dependent days and length of ICU stay.3 Furthermore, malnutrition has been associated with increased mortality in hospital patients.4

More than one in four patients who are admitted to hospital are malnourished5


The National Collaborating Centre for Acute Care (now part of the National Clinical Guideline Centre, NCGC), in their 2006 publication commissioned by NICE ‘Nutrition support for adults: oral nutrition support, enteral tube feeding and parenteral nutrition’ reports "malnutrition is common - many people who are unwell in hospital or the community are likely to eat and drink less than they need." 6

Two nutrition screening surveys undertaken by BAPEN (British Association for Parenteral and Enteral Nutrition) showed 28% of patients who were admitted to hospital were malnourished.5 Nutritional status may be worsened during a hospital stay due to acute illness or major surgery.6

All inpatients should be screened for nutritional status on admission to hospital and at weekly intervals during their stay6

For patients who are unable or unlikely to meet most of their nutritional requirements for long periods of time the need for nutritional support is apparent. In other patients however, the picture might not be as clear and the decision to commence nutritional support can be more difficult.

Formal nutritional assessment is the first step in identifying if your patient may require nutritional support. NICE recommends all inpatients be screened on admission to hospital and at weekly intervals during their stay.6

The goals of formal nutritional assessment are to:7

  • Identify patients who are malnourished or at risk of malnutrition.
  • Collect the informations necessary to create a nutritional care plan.
  • Monitor the adequacy of nutritional therapy.

Methods of nutrition support

The overall aim of nutrition support is to ensure that total nutrient intake provides sufficient energy, protein, micronutrients and fluids to meet the patient’s needs. Nutrition support is delivered through the use of oral supplements, enteral tube feeding and/or parenteral nutrition.

The gastrointestinal tract is bypassed through the administration of nutrients directly into the circulatory system. PN may be used when oral or enteral feeding is contraindicated or insufficient to meet a patient’s requirements. PN is administered either via a central or a peripheral venous catheter.
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Who may need parenteral nutrition?

In patients with intestinal failure of severity sufficient to preclude enteral or oral feeding for long periods, PN is undoubtedly a lifesaver. In other patients (for example those receiving some enteral intake, or those who are adequately nourished and the anticipated duration of starvation or sub-target nutrient intake is unknown), the use of PN can be contentious and the decision to use PN requires careful consideration of the potential risks versus the benefits.

If nutrition support is indicated and the gastrointestinal tract is functioning adequately and is accessible, and enteral feed can be administered safely, then the enteral route should be utilised. If the use of EN has been actively excluded as being inappropriate, inaccessible or inadequate then PN may be indicated.

Conditions that may be associated with a requirement for PN

Intestinal failure due to:

  • Paralytic or mechanical ileus
  • Trauma
  • Radiation injury to small intestine
  • Inflammatory bowel disease in the acute phase causing malabsorption
  • Intestinal resection (short bowel syndrome)
  • Pancreatitis
  • High output fistula
  • Burn injury
  • GI cancer
  • Immaturity (premature babies)

Insufficient enteral/oral feeding


  • Malnutrition is associated with increased morbidity, mortality and treatment costs
  • More than one in four patients who are admitted to hospital are malnourished
  • Patients should be screened for nutritional status on admission to hospital and at weekly intervals during their stay
  • Nutritional support can be provided by oral supplements, EN and/or PN
  • PN provides some or all of a patient’s nutritional requirements directly into a vein
  • If nutritional support is indicated, PN should only be considered if EN is inaccessible, inappropriate or inadequate
  • A range of conditions can be associated with the need for PN, hence PN may be required anywhere in the hospital


  1. Norman K, Pichard C, Lochs H, Pirlich M. Prognostic impact of disease-related malnutrition. Clin Nutr. 2008 Feb; 27(1):5-15. Epub 2007 Dec 3.
  2. Wischmeyer PE. Malnutrition in the acutely ill patient: is it more than just protein and energy? S Afr J Clin Nutr. 2011; 24(3): S1-S7.
  3. Macdonald K, Page K, Brown L, Bryden D. Parenteral nutrition in critical care. Contin Educ Anaesth Crit Care Pain [internet]. 2012 Nov 21 [cited 2016 Feb 1]. Available from doi:10.1093/bjaceaccp/mks056.
  4. Cederholm T, Jägrén C, Hellström K. Outcome of protein-energy malnutrition in elderly medical patients. Am J Med. 1995 Jan; 98(1): 67-74.
  5. Brotherton A, Simmonds N, Stroud M. Malnutrition Matters Meeting Quality Standards in Nutritional Care. Redditch: BAPEN; 2010.
  6. National Collaborating Centre for Acute Care (UK). Nutrition Support for Adults: Oral Nutrition Support, Enteral Tube Feeding and Parenteral Nutrition. London: National Collaborating Centre for Acute Care (UK); 2006 Feb. (NICE Clinical Guidelines, No. 32.) Available from
  7. ASPEN Board of Directors and the Clinical Guidelines Task Force. Guidelines for the use of parenteral and enteral nutrition in adult and pediatric patients. JPEN J Parenter Enteral Nutr. 2002 Jan-Feb; 26 (1 Suppl): 1SA-138SA. Erratum in: JPEN J Parenter Enteral Nutr 2002 Mar-Apr; 26(2): 144.