Feeding the critically ill.
In the ICU, "feed early and full" is mostly wrong. Match feeding to the phase — start low, prefer the gut, and don't chase calories or high protein in week one.
Reviewed June 2026 · verify against current guidelines
Feed To The Phase
Match feeding to the phase.
| Acute, early (days 1-2) | Catabolic and inflamed; the body burns its own stores. Start low (~12 kcal/kg). Permissive underfeeding is fine. Do not overfeed |
|---|---|
| Acute, late (days 3-7) | Stability returns; advance toward target. 25-30 kcal/kg; protein 1.0-1.5 g/kg. Climb slowly |
| Recovery (anabolic) | Rebuilding muscle; requirements rise. Higher energy and protein, paired with rehab. Feed to rebuild |
Early is not full: Starting nutrition early is not the same as advancing to full calories fast.
Phase timing is approximate and overlaps. Reassess daily.
Most trials studied the acute phase; recovery-phase feeding is less well-studied.
Route & Timing
Gut first, but not in shock.
The order
- Oral first, then enteral, then parenteral. Default to the gut.
- Start enteral nutrition within about 48 h if hemodynamically stable.
- Hold enteral feeds in unresuscitated shock (bowel ischemia risk).
- Expecting extubation and eating within 48 h? No tube feeding needed.
Parenteral nutrition
| EN contraindicated | Early PN (36-48 h) is reasonable. Do not just delay. |
|---|---|
| EN insufficient | Do not add supplemental PN in week 1 to chase goals (EPaNIC). |
EN contraindications: shock, obstruction, ileus, major UGI bleed, gut ischemia, high-output fistula.
EN enteral nutritionPN parenteral nutritionUGI upper gastrointestinal
The Numbers
Start low, climb slow.
Calories (kcal/kg/day)
| Start | 12, then increase |
|---|---|
| Target | 25-30, reached over 3-7 days |
| Acute week | Hypocaloric is acceptable; do not overfeed |
Protein (g/kg/day)
| Dose | 1.0-1.5; lower end for most |
|---|---|
| Kidney injury | Reduce; high-dose may harm |
| High protein | ≥2.2 gave no benefit (EFFORT Protein, PRECISe) |
Dose by current or dry weight; obesity uses adjusted weight. Indirect calorimetry best guides targets when available. These are ICU acute-phase targets; ward and recovery needs run higher.
What The Trials Show
The evidence converges.
Landmark trials
| PermiT · EDEN · TARGET | 2012-2018. Permissive or trophic feeding matched full feeding. |
|---|---|
| NUTRIREA-3 | 2023. In shock, low calorie and protein was non-inferior. |
| EFFORT Protein · PRECISe | 2023-24. High-dose protein gave no benefit; possible harm in AKI. |
| EPaNIC | 2011. Early supplemental PN added to enteral feeds did not help. |
Across trials, more calories and more protein in the acute phase did not improve outcomes.
PN parenteral nutritionAKI acute kidney injury
Pitfalls
Stop doing these.
Common errors
- Counting only the tube feed: propofol (1.1 kcal/mL), dextrose, and citrate add calories too.
- Chasing gastric residual volumes (hold only if >500 mL).
- Stopping feeds for every transient blip; deficits add up.
- Using albumin or prealbumin as nutrition markers; they track inflammation.
- Routine vitamin or trace-element supplements without a known deficiency.
Do give thiamine in malnutrition or alcohol use, and watch for refeeding when feeding starts.
Sources
Verify against current guidelines and local protocol before acting.
- Singer P, et al. ESPEN guideline on clinical nutrition in the ICU. Clin Nutr 2019;38:48-79 (practical update 2023).
- Compher C, et al. ASPEN/SCCM guidelines for nutrition support of the critically ill. JPEN 2022 (updates McClave 2016).
- Casaer MP, et al. Early versus Late Parenteral Nutrition in Critically Ill Adults (EPaNIC). NEJM 2011;365:506-517.
- Reignier J, et al. Low versus standard calorie and protein feeding in ventilated shock (NUTRIREA-3). Lancet Respir Med 2023.
- Heyland DK, et al. Higher vs usual protein in the critically ill (EFFORT Protein). Lancet 2023;401:568-576.
- Arabi YM, et al. Permissive Underfeeding or Standard Enteral Feeding (PermiT). NEJM 2015;372:2398-2408.
- TARGET Investigators. Energy-Dense versus Routine Enteral Nutrition. NEJM 2018;379:1823-1834.
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