Nutritional Status Assessment of the Critically Ill Patient


Published: 13 October 2021

Malnutrition, including erosion of lean body mass and depletion of essential nutrients, is very common in critically ill patients as their nutrition status declines (Ziegler 2009).

Malnutrition is associated with impaired immunologic function, and malnourished patients have poorer outcomes after medical treatment or surgery (Leonard 2009).

Early nutritional support should, therefore, be assessed as soon as possible, preferably upon admission, with ongoing monitoring for all critically ill patients to ensure individual needs are identified and catered for to improve outcomes (Singer & Webb 2005).

The Importance of Assessing Nutritional Status

The aim of assessing a patient’s nutritional status is to:

  • Evaluate pre-existing hydration and nutritional conditions
  • Identify any hydration and nutrition-related complications that could affect the outcome
  • Determine the patient’s nutritional requirements
  • Maintain the optimum level of intake and promote adequate utilisation of hydration and food to promote growth, healing and recovery.

(Cresci 2005)

Factors That Affect Nutritional Status in Critically Ill Patients

The most common factors that can affect nutritional status in critically ill patients include:

  • Being unable to drink and eat
  • Vomiting and diarrhoea
  • Constipation
  • Glucose intolerance
  • Renal dysfunction
  • Pain
  • Physical disability
  • Restricted fluid intake
  • Reduced gut motility
  • Fasting before procedures/investigations.

(Jevon 2012)

Assessing a Critically Ill Patient’s Nutritional Status

All patients should undergo nutritional screening on admission to hospital or healthcare settings (NICE 2017). You should follow your local policies and protocols to identify patients at risk of malnutrition and dehydration.

Steps for appropriate management include:

1. Screening:

The screening process categorises patients into groups and those who are ‘at risk’.

A nutritional care plan should be developed, and referral for nutritional support made to an expert/dietitian for more detailed assessment (Kondrup et al. 2003a).

One screening tool used is the malnutrition universal screening tool (MUST) (Russell and Elia 2011), which is used in hospitals, communities and other healthcare settings. It’s used to identify adults who are malnourished, at risk of malnutrition or obese, and it includes management guidelines that can be used to develop a care plan (Malnutrition Advisory Group 2004).

2. Assessment:

A full examination of nutritional, metabolic and functional variables should be conducted, and consideration paid to patient history, current medications, laboratory results, the patient’s ability to swallow and bowel function.

The assessment should provide information leading to an appropriate care plan (Mallet 2013).

3. Monitoring and Outcome:

The effectiveness of the nutritional intervention should regularly be monitored, leading to adjustments in treatment as necessary throughout the patient’s stay.

4. Communication:

Screening and assessment results and the developed nutritional care plan should be communicated to other health professionals when the patient is transferred somewhere else.

Modes of Feeding in Critically Ill Patients

Oral nutrition is generally considered the first line method, but patients who cannot tolerate oral feeding can be fed enterally or parenterally. The route used will depend on:

  • Whether the patient has a functioning GI tract system
  • Which route is appropriate based on the patient’s condition
  • How long feeding will be required.

(Mallet 2013)

Nurse inspecting an enteral feeding pump bag

Enteral Feeding

Enteral feeding involves administering liquid feed via a tube placed in the patient’s stomach, duodenum or jejunum and is the route of choice for critically ill patients where oral feeding is not possible. This method is used if a patient has a functional and accessible GI tract (NICE 2017).

Routes of Enteral Feeding

  • Nasogastric: A tube through the nose into the stomach
  • Nasoduodenal: a tube through the nose into the duodenum
  • Nasojejunal: a tube through the nose into the jejunum
  • Percutaneous endoscopic gastrostomy (PEG): PEG tubes should be considered when enteral feeding is necessary for four weeks or more.

(Marshall & Boyle 2007; NICE 2017)

Best Practice for Enteral Feeding

  • Adhere to best practice feeding protocols
  • Always confirm the tube position before the commencement of feed
  • Always flush the tubes before and after administration of medications
  • Regularly monitor the tube position during feeding
  • Monitor the patient’s vital signs, particularly the airway
  • Keep the head of the bed elevated to 30-45 degrees while administrating feed to reduce the risk of aspiration
  • Increase feed to meet nutritional requirements following local guidelines
  • Ensure feed is in date and administered following the manufacturer’s recommendations
  • Monitor the absorption of feed and follow the prescribed feeding regime
  • Maintain fluid balance
  • Monitor bowel function
  • Monitor the patient’s blood chemistry.

(Jevon 2012)

Parenteral Nutrition

Parenteral nutrition involves the intravenous infusion of nutrients. It’s administrated via a single dedicated lumen either peripherally, via a PICC line, or centrally, via a central venous access device.

This route is used when oral and/or enteral nutrition is unable to fully meet the patient’s nutritional requirements, or when enteral nutrition is contraindicated (Ziegler 2009).

Best Practice for Parenteral Feeding

  • Only use when the enteral route is not possible
  • Administer feed following local protocols, policies and procedures
  • Ensure recent baseline biochemistry has been collected prior to commencing the feed as reviewed by the treating medical team
  • Document the patient’s weight
  • Maintain an accurate fluid balance chart
  • Ensure the access line has been inserted and confirmation has been determined and confirmed by a trained nurse or medical staff
  • Collect all equipment required for the procedure
  • Remove the feed from the medication refrigerator
  • Check the feed prescription order against the prepared order with a registered nurse or doctor
  • Check the patient’s identification at the bedside with a second registered nurse or doctor
  • Confirm the patient, prescription order and ensure there is a light-sensitive cover present
  • Do not use a feed bag if there are signs of contamination
  • Ensure that the entire infusion line is dedicated to the parenteral nutrition
  • Ensure that feed and tubing are regularly changed and clearly labelled at all times
  • Never add anything to a bag of TPN
  • Monitor the patient’s blood chemistry as per local policy
  • Monitor blood glucose levels regularly as per local policy
  • Avoid disconnecting the circuit
  • Monitor the patient for complications, particularly infection around the access line device
  • Regularly flush the line when not in use to maintain patency
  • Ensure the patient has been reviewed by a dietician whilst on parenteral nutrition.

(Jevon 2012; ACT Health 2021; The Royal Hospital for Women 2018)


Nutritional status should be assessed and regularly monitored in all critically ill patients. The method of nutritional support should also be closely monitored, in particular, the patient’s tolerance of it.

Additional Resources

  • ACT Health 2021, Administration of Total Parenteral Nutrition (TPN) – Adults, ACT Government, viewed 13 October 2021, [download link]
  • Cresci, G A 2005, Nutrition Support for the Critically Ill Patient, Boca Raton: Taylor & Francis.
  • Jevon, P, Ewens, B & Pooni, J S 2012, Monitoring the Critically Ill Patient, 3rd edn, John Wiley & Sons Ltd. Chichester.
  • Kondrup, J, Allison, S P, Alia, M, Vellas, B & Plauth, M 2003, ‘ESPEN Guidelines For Nutrition Screening’, Clinical Nutrition, vol. 22, no. 4, pp. 415-21, viewed 20 June 2018,
  • Kondrup, J, Rasmussen, H H, Hamberg, O, Stangam Z & Ad Hoc ESPEN Working Group 2003b, ‘Nutritional Risk Screening (NRS 2002): A New Method Based on an Analysis of Controlled Clinical Trials’, Clinical Nutrition, vol. 22, no. 3, pp. 321-36, viewed 20 June 2018,
  • Leonard, R 2009, ‘Enteral and Parenteral nutrition’, in: Bersten, AD & Sons, N (eds), Oh’s Critical Care Manual, 6th edn, Philadelphia, PA: Butterworth Heinemann Elsevier.
  • Mallet, J, Albarran, J & Richardson, R 2013, Critical Care Manual of Clinical Procedures and Competencies, Oxford: Wiley-Blackwell.
  • Malnutrition Advisory Group 2004, Malnutrition Universal Screening Tool, Redditch: BAPEN.
  • Marshall, A & Boyle, M 2007, ‘Support of Metabolic Function’, in: Elliot, R, Aitken, L M & Chaboyer, W (eds), ACCCN’s Critical Care Nursing, Marrickville, NSW: Mosby Elsevier.
  • National Institute for Health and Care Excellence 2017, Nutrition Support for Adults: Oral Nutrition Support, Enteral Tube Feeding and Parenteral Nutrition, NICE, viewed 20 June 2018,
  • The Royal Hospital for Women 2018, Parenteral Nutrition In Newborns, South Eastern Sydney Local Health District, viewed 13 October 2021,
  • Russell, C A & Elia, M 2011, Nutrition Screening Survey in the UK and Republic of Ireland in 2010, Redditch: BAPEN.
  • Scott, A, Skerrat, S & Adam, S 1998, Nutrition for the Critically ill: A Practical Handbook, London: Arnold.
  • Singer, M & Webb, A 2005, Oxford Handbook of Critical Care, 2nd edn, Oxford: Oxford University Press.
  • Ziegler, T R 2009, ‘Parenteral Nutrition in the Critically Ill Patient’, New England Journal of Medicine, vol. 361, pp. 1088-97.


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Lydia Nabwami is registered nurse who has worked in various healthcare settings including cardiac ward, cardiac critical care unit (ITU), general ITU, A&E department, nursing homes and community nursing. She uses her experience as a RN to write well-researched content that helps to attract and motivate audiences. Lydia is also a freelance writer for hire with specialisation in health writing and has helped numerous companies with their content needs. Her work has appeared on sites such as Caring Village, Reachout, Lisa Nelson RD and more. When she isn’t writing, you can find her listening to motivational speeches, keeping active or playing with her two daughters. Contact Lydia or visit her website at for more information on her services.