Enteral vs Parenteral Feeding on ICU

A 70-year-old man had been an inpatient on the intensive care unit for nearly 40 days after a complicated recovery following mitral valve replacement. He was being gradually weaned from the ventilator via tracheostomy but required no other invasive organ support. His intensive care unit stay had been complicated by recurrent respiratory sepsis treated with antibiotics and aggressive physiotherapy. Up until this point he had been fed by a nasogastric tube but began to exhibit signs suggestive of impaired absorption including large nasogastric aspirates and a requirement for higher levels of parenteral electrolyte administration.

Prokinetic treatment with metoclopramide 10mg TDS for 24 hours failed to improve the high aspirate levels which remained in excess of 300ml every four hours. Erythromycin 250mg BD was added with little improvement. Following discussion with gastroenterology colleagues an agreement to place a post-pyloric nasojejunal feeding tube was made; unfortunately this procedure was delayed by a further 48 hours as no endoscopist was free to attend. Parenteral feeding was initiated at this point in order to maintain calorific intake.

Compare enteral and parental nutrition.

Stephen Shepherd

Malnutrition is common in patients admitted to hospital and associated with an increased risk of death up to two years after assessment.(1) The prevalence on ITU has been estimated at up to 40% with the majority of critically ill patients requiring nutritional support.(2,3) General benefits of this include improved wound healing, improved gastrointestinal permeability, improved clinical outcomes and a reduced length of stay.(3) Traditional teaching holds that enteral feeding is superior to parenteral feeding due to a lower complication rate but neither form of support is without risk; traditionally held concerns regarding an increased risk of infection and hyperglycaemia may be of less concern with more modern parenteral nutrition whereas enteral feeding may be associated with high gastric residuals and increased risk of ventilator associated pneumonia.(4,5) A meta-analysis of enteral versus parenteral nutrition demonstrated in particular that parenteral nutrition had significant mortality and anti-infectious benefits over the late institution of enteral feeding.(5)

Early enteral feeding where successful appears to be the best option yet is not universally practiced.(3,6) The use of prokinetics is relatively widespread with evidence of reduced gastric residuals, although this effect is inconsistent(7) and there is no evidence of improved calorific intake.(8) Dopamine agonists do not appear superior to motilin analogues and vice versa.(8) Similarly, post-pyloric tube placement, although it reduces gastric residual volumes appears to offer no benefit in terms of target calorific rate or the volume of feed successfully administered.(9) Although widely used, the use of gastric residual volumes to determine ‘intolerance’ to feed promotes inappropriate cessation of nutrition and cannot be used to predict the risk of aspiration.(10) As yet, no trial has directly compared early administration of enteral or parenteral therapy and the ongoing CALORIES trial will examine this question in more detail.


Lessons Learnt
It appears that successful nutritional support must be administered early and that the parenteral nutrition should be considered more contemporaneously in those who do not meet nutritional goals. The utility of gastric residual volumes to determine the ‘efficacy’ of feeding is questionable, as is the use of prokinetics and post-pyloric feeding. In patients such as this, parenteral therapy may offer better outcome than traditional models of enteral feeding.



  1. Middleton MH, Nazarenko G, Nivison-Smith I, Smerdely P. Prevalence of malnutrition and 12-month incidence of mortality in two Sydney teaching hospitals. Intern Med J. 2001 Nov.;31(8):455–61.
  2. Cangelosi MJ, Auerbach HR, Cohen JT. A clinical and economic evaluation of enteral nutrition. Curr Med Res Opin. 2011 Feb.;27(2):413–22.
  3. Gramlich L, Kichian K, Pinilla J, Rodych NJ, Dhaliwal R, Heyland DK. Does enteral nutrition compared to parenteral nutrition result in better outcomes in critically ill adult patients? A systematic review of the literature. Nutrition [Internet]. 2004 Oct.;20(10):843–8. Available from: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=15474870&retmode=ref&cmd=prlinks
  4. Doig GS, Simpson F, Finfer S, Delaney A, Davies AR, Mitchell I, et al. Effect of evidence-based feeding guidelines on mortality of critically ill adults: a cluster randomized controlled trial. JAMA. 2008 Dec. 17;300(23):2731–41.
  5. Simpson F, Doig GS. Parenteral vs. enteral nutrition in the critically ill patient: a meta-analysis of trials using the intention to treat principle. Intensive Care Med. 2004 Dec. 9;31(1):12–23.
  6. Dhaliwal R, Heyland DK. Nutrition and infection in the intensive care unit: what does the evidence show? Curr Opin Crit Care. 2005 Oct.;11(5):461–7.
  7. DeLegge MH. Managing gastric residual volumes in the critically ill patient: an update. Current Opinion in Clinical Nutrition and Metabolic Care. 2011 Mar.;14(2):193–6.
  8. MacLaren R, Kiser TH, Fish DN, Wischmeyer PE. Erythromycin vs metoclopramide for facilitating gastric emptying and tolerance to intragastric nutrition in critically ill patients. Journal of Parenteral and Enteral Nutrition. 2008 Jul.;32(4):412–9.
  9. Davies AR, Froomes PRA, French CJ, Bellomo R, Gutteridge GA, Nyulasi I, et al. Randomized comparison of nasojejunal and nasogastric feeding in critically ill patients. Critical Care Medicine. 2002 Mar.;30(3):586–90.
  10. McClave SA, Snider HL. Clinical Use of Gastric Residual Volumes as a Monitor for Patients on Enteral Tube Feeding. Journal of Parenteral and Enteral Nutrition. 2002 Nov. 1;26(6 Suppl):S43–S50.

One thought on “Enteral vs Parenteral Feeding on ICU

  1. There have been a few important papers published since this 2013 review. These are covered by TBL @WICSBottomLine and include:

    CALORIES: Early nutritional support through the parenteral route is neither more harmful nor more beneficial than through the enteral route. Enteral feeding does increase episodes of vomiting and hypoglycaemia but with no evidence of harm or nosocomial infection. Daily calorific targets were rarely achieved in this study (< 40% in both groups). This reflects a possible deficiency in our feeding protocols and adherence within UK and highlights the need for this to be addressed.


    PermiT: This trial has not demonstrated a moderate survival benefit from permissive underfeeding with moderate caloric intake (around 50% of target calories) and maintenance of full protein requirement (1.2-1.5g per kg per day). A small survival benefit may exist but this study was not large enough to detect one. Permissive underfeeding with full protein requirement appears safe in critically ill patients.


    PYTHON: Allowing patients with severe pancreatitis three to four days to initiate oral intake appears to be safe and effective. This can reduce the discomfort, cost and complications associated with tube feeding in these patients. Although well-conducted this was a relatively small trial, and future data may change this picture



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