ICU · GI/Nutrition
Nutrition in the ICU
Also known as Critical illness nutrition · Enteral nutrition (EN) · Parenteral nutrition (PN) · Early enteral nutrition · Refeeding syndrome · ESPEN guidelines
Nutrition is a critical component of ICU care. Early enteral nutrition is the default — the landmark trials initiated feeding within 24-36 hours — while early supplemental parenteral nutrition is harmful (EPaNIC: late PN meant fewer infections and shorter ventilation). NUTRIC score stratifies nutrition risk (high NUTRIC = patient who benefits most from adequate delivery). Energy: normocaloric 20-25 kcal/kg/day (NUTRIREA-2); permissive underfeeding (40-60% of calories with protein maintained) was as safe as full feeding (PermiT) and an extra ~600 kcal/day did not improve survival (TARGET). Protein: achieving at least 80% of the prescribed protein dose was associated with lower mortality (Nicolo). Refeeding syndrome: definitions vary but centre on electrolyte disturbances within 72 hours — check phosphate/Mg/K before feeding and watch daily; once it develops, protocolised caloric restriction is the supported management (Doig: 91% vs 78% alive at day 60). Glutamine: REDOX showed harm in multi-organ failure — not routinely recommended. Gastric residual volume: not monitoring GRV at all was non-inferior for VAP (REGANE).
Checked against its sources on 3 Sept 2026
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Red flags
- Refeeding syndrome: phosphate drops rapidly when feeding starts after starvation — check, replace, start slow
- Do NOT chase full calories early — calorie restraint is safe (PermiT, EDEN) and extra calories do not help (TARGET)
- Always give THIAMINE before starting feed in at-risk patients (alcoholics, malnourished)
- A gastric residual volume number decides nothing — REGANE: not monitoring GRV at all was non-inferior for VAP; judge intolerance on vomiting and regurgitation
- High NUTRIC = patient benefits most from adequate protein-calorie delivery; low NUTRIC = underfeeding tolerated
- REDOX: high-dose glutamine may HARM in multi-organ failure — do NOT routinely supplement
- Routine supplemental PN within the first week increases infection and prolongs ventilation (EPaNIC, PEPaNIC)
Meet the patient
A 49-year-old man with chronic alcohol dependence is admitted with aspiration pneumonia and sepsis, intubated and ventilated. He has eaten almost nothing for ten days; his BMI is 15.8, phosphate 0.55 mmol/L, magnesium 0.45 mmol/L, potassium 3.0 mmol/L. The registrar wants to hang full-strength feed at 50 mL/h to "meet his caloric target immediately". [13]
That one plan hides the two questions the whole topic turns on: when do I feed, and how fast? Get them right — early EN, restrained calories, electrolytes watched — and he comes through the week; get them wrong and he risks the precipitous electrolyte shifts of refeeding syndrome or the infections of premature PN. [2][4]
References16ShowHide
- [1]Singer P, Blaser AR, Berger MM, et al. ESPEN guideline on clinical nutrition in the intensive care unit Clin Nutr, 2019.PMID 30348463
- [2]Friedli N, Stanga Z, Sobotka L, et al. Revisiting the refeeding syndrome: Results of a systematic review Nutrition, 2017.PMID 28087222
- [3]Heyland DK, Dhaliwal R, Jiang X, et al. Identifying critically ill patients who benefit the most from nutrition therapy: the development and initial validation of a novel risk assessment tool Crit Care, 2011.PMID 22085763
- [4]Casaer MP, Mesotten D, Hermans G, et al. Early versus late parenteral nutrition in critically ill adults N Engl J Med, 2011.PMID 21714640
- [5]Arabi YM, Aldawood AS, Haddad SH, et al. Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults N Engl J Med, 2015.PMID 25992505
- [6]Harvey SE, Parrott F, Harrison DA, et al. Trial of the route of early nutritional support in critically ill adults N Engl J Med, 2014.PMID 25271389
- [7]Reignier J, Boisramé-Helms J, Brisard L, et al. Enteral versus parenteral early nutrition in ventilated adults with shock: a randomised, controlled, multicentre, open-label, parallel-group study (NUTRIREA-2) Lancet, 2018.PMID 29128300
- [8]Rice TW, Wheeler AP, Thompson BT, et al. Initial trophic vs full enteral feeding in patients with acute lung injury: the EDEN randomized trial JAMA, 2012.PMID 22307571
- [9]Heyland D, Muscedere J, Wischmeyer PE, et al. A randomized trial of glutamine and antioxidants in critically ill patients N Engl J Med, 2013.PMID 23594003
- [10]Chapman M, Peake SL, Bellomo R, et al. Energy-Dense versus Routine Enteral Nutrition in the Critically Ill N Engl J Med, 2018.PMID 30346225
- [11]Fivez T, Kerklaan D, Mesotten D, et al. Early versus Late Parenteral Nutrition in Critically Ill Children N Engl J Med, 2016.PMID 26975590
- [12]Reignier J, Mercier E, Le Gouge A, et al. Effect of not monitoring residual gastric volume on risk of ventilator-associated pneumonia in adults receiving mechanical ventilation and early enteral feeding: a randomized controlled trial JAMA, 2013.PMID 23321763
- [13]Doig GS, Simpson F, Heighes PT, et al. Restricted versus continued standard caloric intake during the management of refeeding syndrome in critically ill adults: a randomised, parallel-group, multicentre, single-blind controlled trial Lancet Respir Med, 2015.PMID 26597128
- [14]Nicolo M, Heyland DK, Chittams J, et al. Clinical Outcomes Related to Protein Delivery in a Critically Ill Population: A Multicenter, Multinational Observation Study JPEN J Parenter Enteral Nutr, 2016.PMID 25900319
- [15]Puthucheary ZA, Rawal J, McPhail M, et al. Acute skeletal muscle wasting in critical illness JAMA, 2013.PMID 24108501
- [16]Finfer S, Chittock DR, Su SY, et al. Intensive versus conventional glucose control in critically ill patients N Engl J Med, 2009.PMID 19318384