An e-learning resource for healthcare professionals
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.
Different hospitals and units have different arrangements for undertaking nutritional screening and assessment, and where the
responsibilities of the different professions lie. If you are not already familiar with your local policy you may like to familiarise yourself with this for your
working practice going forward.
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.
EN and PN are not mutually exclusive; supplemental parenteral nutrition (SPN) can be used when nutritional requirements cannot be met
through the enteral route alone.
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
Radiation injury to small intestine
Inflammatory bowel disease in the acute phase causing malabsorption
At the time of writing there is no universally agreed
definition as to what constitutes insufficient enteral feeding and how
this can be adequately measured objectively. The heterogeneity of
the patient population requiring nutritional support is such that it
may be reasonable to assume the criteria for ‘insufficient enteral/oral
feeding’ in one patient and how long this can be tolerated for may be
very different to the criteria in another patient. Your hospital or unit
may have its own in-house definition of what constitutes insufficient
(or inadequate) enteral or oral feeding which you may like to refer to.
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
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.
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.
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.
Cederholm T, Jägrén C, Hellström K. Outcome of protein-energy malnutrition in elderly medical patients. Am J Med. 1995 Jan; 98(1): 67-74.
Brotherton A, Simmonds N, Stroud M. Malnutrition Matters Meeting Quality Standards in Nutritional Care. Redditch: BAPEN; 2010.
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
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.