[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anaesthesia and ICU](https://durgical.com/en/anaesthesia/) › [Critical care (ICU)](https://durgical.com/en/anaesthesia/areas/critical-care/) › Nutrition in the ICU: enteral first

# Nutrition in the ICU: enteral first

- Concept

Seriously ill patients need food; the best route is a tube into the stomach, and a vein is used only when the gut cannot be used.

Updated Nov 13, 2026

## Key points

- Enteral first: start within 24 to 48 hours once resuscitated; it protects the gut barrier and causes fewer infections than PN.
- Contraindications to EN: bowel obstruction or ischaemia, uncontrolled shock with rising vasopressors, abdominal compartment syndrome, severe active GI bleeding, high-output fistula.
- Confirm a blindly placed feeding tube position, usually on X-ray, before the first feed.
- PN is for a gut that cannot be used or EN that falls short; well-nourished patients wait several days, malnourished ones start earlier.
- Refeeding syndrome: falling phosphate, potassium and magnesium with thiamine deficiency; start slowly, give thiamine first and monitor daily.

## What it is

Critical illness drives a catabolic state: muscle protein breaks down fast, and patients who stay in the ICU for days lose strength and function. Nutrition support aims to limit this loss without overfeeding. The first step is to screen nutritional risk at admission, using a validated tool and the patient's history (weight loss, intake before admission, frailty). Enteral nutrition (EN), through a tube into the stomach or small bowel, is the preferred route: it keeps the gut barrier and gut immunity working, is linked to fewer infections than parenteral feeding, and costs less. It is started early, usually within 24 to 48 hours, once the patient is resuscitated and not on rising vasopressor support, often at a low rate that is increased over several days. Gastric feeding is the first choice; post-pyloric feeding is used for intolerance or high aspiration risk. Parenteral nutrition (PN) delivers glucose, amino acids, lipids, electrolytes, vitamins and trace elements into a vein; it is used when the gut cannot be used or EN cannot meet needs, and in well-nourished patients it is usually delayed for several days, while severely malnourished patients start earlier. Both routes carry the risk of refeeding syndrome in malnourished patients, and both need close control of glucose and electrolytes.

## Key points

- Screen nutritional risk at admission and reassess as the stay lengthens.
- Avoid overfeeding in the first days, when the body still produces much of its own glucose; increase intake gradually.
- Protein needs are higher than in health; indirect calorimetry, when available, is the most accurate way to estimate energy needs.
- Keep the head of the bed raised and use prokinetics for intolerance; routine reliance on gastric residual volumes is no longer advised in many protocols.
- Control glucose with an insulin protocol aiming for a moderate range rather than tight control, which raises the risk of hypoglycaemia.
- PN needs a central line (or a peripheral line for low-osmolarity solutions) and strict asepsis.

## How it works

- Nutrients in the gut lumen feed the enterocytes, maintain tight junctions and gut-associated lymphoid tissue, and limit bacterial translocation.
- PN bypasses the gut: it reliably delivers nutrients but brings line infection, hyperglycaemia, liver dysfunction and fluid load.
- In refeeding, insulin release moves phosphate, potassium and magnesium into cells and consumes thiamine, so blood levels fall fast.

## Enteral and parenteral nutrition compared

| Aspect | Enteral | Parenteral |
| --- | --- | --- |
| Route | Nasogastric or post-pyloric tube, gastrostomy | Central or peripheral vein |
| When | First choice once resuscitated | Gut unusable or EN not meeting needs |
| Main risks | Aspiration, diarrhoea, tube misplacement, intolerance | Line infection, hyperglycaemia, liver dysfunction, overfeeding |
| Both | Refeeding syndrome, electrolyte disturbance | Refeeding syndrome, electrolyte disturbance |

## In practice

- Diarrhoea on EN: check for C. difficile and laxative or sorbitol-containing drugs before blaming the feed.
- Vomiting, distension or high aspirates: check for obstruction and abdominal pressure, slow the feed and add a prokinetic or move post-pyloric.
- A blindly placed tube can enter the airway: never feed before the position is confirmed.
- Patients at risk of refeeding (malnourished, alcohol use, long fasting) need slow increases, thiamine and electrolyte checks.
- Fever on PN: suspect a line infection and culture the line.

## Next step

- Write the feeding plan in the chart: route, target, rate of increase and the reason for any pause.
- Ask the nutrition team or dietitian to set energy and protein targets and review them as the patient changes.
- Monitor glucose, phosphate, potassium and magnesium daily for the first days, more often in patients at risk of refeeding.
- Call a senior if the abdomen becomes distended or painful, lactate rises or there is vomiting on feed, as these may signal bowel ischaemia.
- Plan for swallowing assessment, oral intake and rehabilitation after extubation; continue nutrition support after the ICU if needed.

## Test yourself

Think of the answer, then tap the question to see it.

## Why is enteral nutrition preferred over parenteral nutrition in the ICU?

It keeps the gut barrier and gut immunity working, is associated with fewer infections and is cheaper and simpler.

## What are three contraindications to starting enteral nutrition?

Bowel obstruction or ischaemia, uncontrolled shock with rising vasopressor needs, and abdominal compartment syndrome; also severe active GI bleeding or a high-output fistula.

## Which electrolytes fall in refeeding syndrome, and why?

Phosphate, potassium and magnesium: insulin released by feeding drives them into cells, and thiamine is used up, so blood levels fall quickly.

## What must be done before the first feed through a blindly placed nasogastric tube?

Confirm the tube position, usually with an X-ray, because it can be misplaced in the airway.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anaesthesia/nutrition-in-the-icu-enteral-first/)

## Elsewhere in DurgiPedia

- [Enteral feeding: checking the tube, feeding and care](https://durgical.com/en/nursing/enteral-feeding-checking-the-tube-feeding-and-care/)
- [Preparing parenteral medication: ampoules, vials and reconstitution](https://durgical.com/en/nursing/preparing-parenteral-medication-ampoules-vials-and-reconstitution/)
- [Nutrition screening and helping patients eat](https://durgical.com/en/nursing/nutrition-screening-and-helping-patients-eat/)
- [Capillary blood glucose testing](https://durgical.com/en/nursing/capillary-blood-glucose-testing/)
- [Severe acute malnutrition: marasmus and kwashiorkor](https://durgical.com/en/general-pathology/severe-acute-malnutrition-marasmus-and-kwashiorkor/)

## Connections

## Related 6

- [The ICU daily bundle (FAST HUGS and similar checklists)](https://durgical.com/en/anaesthesia/the-icu-daily-bundle/)
- [Stress-ulcer prophylaxis: who needs it](https://durgical.com/en/anaesthesia/stress-ulcer-prophylaxis-who-needs-it/)
- [Ventilator-associated pneumonia: the prevention bundle](https://durgical.com/en/anaesthesia/ventilator-associated-pneumonia-the-prevention-bundle/)
- [Central lines in the ICU: choice, checks and removal](https://durgical.com/en/anaesthesia/central-lines-in-the-icu-choice-checks-and-removal/)
- [Catheter-related bloodstream infection: prevention and response](https://durgical.com/en/anaesthesia/catheter-related-bloodstream-infection-prevention-and-response/)
- [Intra-abdominal hypertension and abdominal compartment syndrome](https://durgical.com/en/anaesthesia/intra-abdominal-hypertension-and-abdominal-compartment-syndrome/)

## Related conditions 5

- [Refeeding syndrome](https://durgical.com/en/conditions/refeeding-syndrome/)
- [Aspiration pneumonia and pneumonitis](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/)
- [Clostridioides difficile infection](https://durgical.com/en/conditions/clostridioides-difficile-infection/)
- [Wernicke encephalopathy (thiamine deficiency)](https://durgical.com/en/conditions/wernicke-encephalopathy/)
- [Malnutrition and unintentional weight loss in older adults](https://durgical.com/en/conditions/malnutrition-and-unintentional-weight-loss-in-older-adults/)

## In Pharmacology 4

- [Metoclopramide](https://durgical.com/en/pharmacology/metoclopramide/)
- [Erythromycin](https://durgical.com/en/pharmacology/erythromycin/)
- [Insulins](https://durgical.com/en/pharmacology/classes/insulins/)
- [Thiamine](https://durgical.com/en/pharmacology/thiamine/)

[← All of anaesthesia](https://durgical.com/en/anaesthesia/)

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: [Enteral Feeding](https://www.ncbi.nlm.nih.gov/books/NBK532876/) (StatPearls (NCBI Bookshelf), 2022); [Total Parenteral Nutrition](https://www.ncbi.nlm.nih.gov/books/NBK559036/) (StatPearls (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anaesthesia/nutrition-in-the-icu-enteral-first/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anaesthesia/nutrition-in-the-icu-enteral-first/