ESPEN Guidelines for ICU Nutrition (2023 Practical Guideline)

1. Nutritional Assessment

• Perform a nutritional risk screen on all ICU patients at admission (e.g., NRS-2002 or NUTRIC score).
• Assess body weight, BMI, and prior dietary intake.
• Indirect calorimetry (IC) is the preferred method to measure energy expenditure when available.
• If IC is unavailable, use VO2 from pulmonary artery catheter or VCO2 from ventilator (VCO2 × 8.19) as the next-best option.
• Predictive equations (e.g., Penn State, Mifflin-St Jeor) are less accurate but acceptable as a last resort.

2. Timing of Nutrition

3. Route of Nutrition

• EN should be the first-line route in all patients without contraindications.
• EN reduces ICU infections compared to PN (RR 0.64, 95% CI 0.48-0.87), though this difference diminishes when similar calories are given.
• Gastric EN is the default; switch to post-pyloric EN if gastric intolerance persists despite prokinetics.
• Gastric residual volume (GRV) cut-off: do not interrupt EN if GRV < 500 mL (some protocols use 250 mL).
• Head of bed elevation to 30-45° should be maintained.

• Use PN as supplement only when EN is insufficient or contraindicated.
• Avoid early PN (before day 3-7) to prevent overfeeding complications.
• Use a central venous catheter for PN with osmolarity > 850 mOsm/L; peripheral PN acceptable for lower-osmolarity formulas.

4. Energy Targets

• Avoid overfeeding at all times - it is associated with hyperglycemia, fatty liver, increased CO2 production, and prolonged ventilation.
• In obese patients (BMI > 30): use hypocaloric, high-protein feeding; target 11-14 kcal/kg actual body weight/day or 22-25 kcal/kg ideal body weight.

5. Protein Targets

• Standard: 1.3 g/kg/day (actual body weight), progressed gradually after the acute phase
• ESPEN range: 1.2-1.5 g/kg/day in most critically ill patients
• Higher protein (up to 2.0 g/kg/day) considered in burns, trauma, and prolonged ICU stay (chronic critical illness)
• Obese patients: 1.3 g/kg/day ideal body weight (some guidelines suggest up to 2.0 g/kg IBW)
• CRRT/renal replacement: up to 1.5-1.7 g/kg/day due to losses

A 2024 systematic review (PMID 38777455) found that guideline-recommended protein intakes did not consistently reduce mortality - optimal protein dosing in the ICU remains an area of active study.

6. Carbohydrates and Lipids

• Maximum glucose infusion rate: 5 mg/kg/min
• Target blood glucose: 140-180 mg/dL (7.8-10 mmol/L)
• Avoid both hypoglycemia and tight glucose control (target < 110 mg/dL increases mortality risk)

• Should comprise 30-50% of non-protein calories
• Use lipid emulsions containing mixed oils (including olive oil or fish oil/omega-3) rather than pure soybean oil
• Limit soybean oil-based lipid emulsions to reduce pro-inflammatory omega-6 load
• Maximum lipid infusion rate: 1.5 g/kg/day
• Fish oil-enriched formulas may benefit post-surgical and septic patients

7. Micronutrients and Immunonutrition

• Supplement all ICU patients receiving PN with standard micronutrient doses (vitamins + trace elements daily)
• High-dose antioxidant supplementation (selenium, vitamins C, E) is not recommended as routine
• Monitor zinc, selenium, copper, and vitamins in patients on prolonged nutrition support

8. Special Conditions

Renal Failure / CRRT

• Continue EN; do not restrict protein excessively.
• Protein: up to 1.5-1.7 g/kg/day on CRRT.
• Adjust electrolyte content (reduce phosphate, potassium if needed).

Liver Failure

• EN preferred; initiate early.
• Branched-chain amino acid (BCAA) enriched formulas may help in hepatic encephalopathy.
• Avoid excessive protein restriction - most patients tolerate standard protein targets.

Pancreatitis

• In mild-moderate pancreatitis: oral/EN feeding within 24-48 h.
• In severe pancreatitis: early EN (nasogastric or nasojejunal) recommended over PN.

Burns

• Very high energy (up to 35 kcal/kg/day) and protein (1.5-2.0 g/kg/day) requirements.
• Enteral glutamine as above.

Abdominal Surgery / Post-op

• Early EN (within 24 h) after surgery if no anastomotic concern.
• Immune-enhancing formulas (arginine, omega-3, nucleotides) peri-operatively in high-risk surgery patients (Grade A in ESPEN surgical guidelines).

Obesity (BMI > 30)

• Hypocaloric, high-protein strategy.
• Target: 11-14 kcal/kg actual BW, protein 1.3 g/kg IBW.

9. Monitoring and Reassessment

• Reassess nutritional tolerance and adequacy daily.
• Monitor gastric residual volumes, abdominal distension, and bowel function.
• Track weight trends (fluid shifts confound this in the ICU).
• Use indirect calorimetry to reassess EE at key transitions (phase change, clinical deterioration).
• Monitor blood glucose every 1-4 hours during insulin infusion.
• Weekly assessment of micronutrient status in prolonged ICU stays.

10. Refeeding Syndrome Prevention

• Identify high-risk patients: prolonged starvation, severe malnutrition, chronic alcoholism, BMI < 16, negligible intake for > 10 days.
• Start nutrition slowly in at-risk patients.
• Monitor and replace phosphate, magnesium, potassium, and thiamine before and during refeeding.
• Thiamine 100-300 mg IV before starting feeding in at-risk patients.

Key Differences from 2019 Guideline

• Stronger emphasis on progressive caloric delivery in the early phase (avoid full feeding in first 48-72 h).
• Clearer cut-off of 48 h for initiating early EN and for contraindications.
• Further clarification that delay of PN beyond day 3 (if EN not tolerated) may confer additional benefit.
• IV glutamine contraindication in multi-organ failure reinforced.
• Flow charts added for practical bedside use.

Supplement: The 2022 ESPEN micronutrient guideline (PMID 35365361) and the 2024 short micronutrient guide (PMID 38350290) provide detailed dosing for trace elements and vitamins - relevant for prolonged ICU nutrition support. For patients with AKI/CKD, the 2024 ESPEN kidney disease guideline (PMID 39178492) applies.