Early Nutrition
Initiate enteral nutrition within 24–48 hours of ICU admission in hemodynamically stable patients (ASPEN/SCCM 2016, ESPEN 2019).
Caloric Targets
Adults: 25–30 kcal/kg/day. Avoid overfeeding in acute phase. Use indirect calorimetry when available (Grade A).
Protein Priority
Protein: 1.2–2.0 g/kg/day. Higher ranges for burns, trauma, and multi-organ failure. Essential to mitigate muscle wasting.
Metabolic Phases in Critical Illness
Ebb Phase (0–24 hrs)
Hypometabolic state. ↓ Cardiac output, ↓ O₂ consumption, ↓ Core temperature. Focus on resuscitation, not nutrition. Hyperglycemia due to stress hormones (cortisol, catecholamines, glucagon).
Flow Phase – Acute Catabolic (Day 1–7)
Hypermetabolic, hypercatabolic. ↑ REE 20–60%. Massive protein catabolism (up to 250g muscle/day). Initiate trophic feeding → advance to target. Permissive underfeeding (70% of target) may be considered in obese patients.
Anabolic Recovery Phase (Day 7+)
Transition to anabolism. Full caloric targets. Increase protein to 1.5–2.5 g/kg/day. Rehabilitation nutrition: combine with early mobilization. Monitor refeeding syndrome risk.
Guiding Principles (ASPEN/ESPEN/SCCM)
EN preferred over PN (↓ infectious complications, ↓ mortality)
Gastric feeding as first-line; post-pyloric if high aspiration risk
Do NOT delay EN for absence of bowel sounds or flatus
Measure gastric residual volumes (GRV); do not hold feeds for GRV <500 mL
Supplemental PN only if EN fails to meet >60% target by Day 7
Glycemic control: target 140–180 mg/dL (avoid hypoglycemia)
Nutritional Risk Screening
| Tool | Population | Parameters | High Risk Score |
|---|---|---|---|
| NRS-2002 | Adults | BMI, weight loss, food intake, disease severity | ≥3 |
| NUTRIC Score | ICU Adults | Age, APACHE II, SOFA, comorbidities, days hospital→ICU, IL-6 | ≥5 (without IL-6) |
| STRONGkids | Pediatric | Subjective assessment, high-risk disease, intake/losses, weight loss | ≥4 |
| SGNA | Pediatric | History, physical exam, functional capacity | B or C |
Energy Requirement Estimation
Gold Standard: Indirect Calorimetry (IC)
Measures REE via VO₂ and VCO₂. Weir equation: REE = (3.941 × VO₂ + 1.106 × VCO₂) × 1440
RQ = VCO₂/VO₂ → Indicates substrate utilization (0.7=fat, 0.85=mixed, 1.0=carbs, >1.0=lipogenesis/overfeeding)
Predictive Equations (when IC unavailable)
Harris-Benedict (adjusted)
Males: 66.5 + (13.75×W) + (5.003×H) - (6.775×A)
Females: 655.1 + (9.563×W) + (1.850×H) - (4.676×A)
Apply stress factor: 1.2–1.5×
Penn State (ICU-validated)
REE = HBE(0.85) + VE(33) + Tmax(175) - 6433
Simple Rule of Thumb
25–30 kcal/kg/day (actual body weight, unless obese)
Obesity Adjustments (BMI ≥30)
Use 11–14 kcal/kg actual BW/day OR 22–25 kcal/kg ideal BW/day. Protein: ≥2.0 g/kg IBW/day. Hypocaloric, high-protein approach preferred.
Protein Requirements by Condition
| Clinical Condition | Protein (g/kg/day) | Notes |
|---|---|---|
| General ICU | 1.2–2.0 | Higher end for surgical/trauma |
| Burns (>20% TBSA) | 1.5–2.5 | Massive protein losses via wounds |
| Sepsis/MODS | 1.5–2.0 | Advance gradually after resuscitation |
| CRRT/Dialysis | 2.0–2.5 | Amino acid losses via effluent (10–15g/day) |
| AKI (no RRT) | 0.8–1.0 | Do not restrict protein to delay RRT |
| Hepatic Encephalopathy | 1.2–1.5 | Do NOT restrict protein; use BCAA if intolerant |
Enteral Nutrition Protocol
Initiation & Advancement
Start
- • Trophic feeding: 10–20 mL/hr (or 500 kcal/day)
- • Isotonic, polymeric formula as default
- • Start within 24–48h of admission
- • Head of bed elevation ≥30–45°
Advance
- • Increase by 10–25 mL/hr every 4–8 hours
- • Target: 80% of goal by 48–72 hours
- • Hold for hemodynamic instability (MAP <60, rising lactate, escalating vasopressors)
- • Resume at prior rate once stable
Formula Selection
| Formula Type | Indication | Examples |
|---|---|---|
| Standard Polymeric (1.0 kcal/mL) | Default for most ICU patients | Osmolite, Jevity, Nutrison |
| High-Protein (1.0–1.5 kcal/mL) | Surgical, trauma, burns | Promote, Fresubin HP |
| Calorie-Dense (1.5–2.0 kcal/mL) | Fluid restriction (CHF, renal, ARDS) | TwoCal, Nutrison Energy |
| Semi-Elemental/Peptide-Based | Malabsorption, short bowel, pancreatitis | Peptamen, Vital, Survimed |
| Diabetes-Specific | Persistent hyperglycemia | Glucerna, Diben |
| Immune-Modulating | Major elective surgery (perioperative) | Impact, Oxepa (arginine, omega-3, nucleotides) |
Managing EN Intolerance
High GRV (>500 mL)
→ Prokinetics: Metoclopramide 10mg IV q6h or Erythromycin 250mg IV q12h. Switch to post-pyloric if persistent.
Diarrhea
→ Rule out C. diff. Consider fiber-containing formula, reduce osmolality. Avoid holding feeds; switch to continuous infusion.
Vomiting/Regurgitation
→ HOB >45°, continuous infusion, post-pyloric tube, prokinetics. Hold if active aspiration.
Abdominal Distension
→ Measure abdominal girth. Rule out ileus, bowel obstruction, abdominal compartment syndrome. Reduce rate or hold.
Access Routes
Nasogastric (NG/OG)
- • First-line access
- • Verify placement: X-ray, pH <5
- • Bolus or continuous
- • Short-term (<4–6 weeks)
Nasojejunal (NJ) / Post-pyloric
- • High aspiration risk
- • Gastroparesis/GRV intolerance
- • Continuous infusion only
- • Endoscopic/fluoroscopic placement
PEG / Surgical Jejunostomy
- • Long-term (>4–6 weeks)
- • PEG: percutaneous endoscopic
- • Jejunostomy: post-gastric surgery
- • Lower risk of displacement
Parenteral Nutrition (PN)
Key Principle
PN is NOT first-line. Use only when EN is contraindicated, insufficient (<60% target by Day 7), or functionally impossible. Early PN (Day 1–3) in well-nourished patients increases infections (EPaNIC trial).
Indications for PN
PN Composition & Prescribing
| Component | Daily Requirement | Max Rate / Notes |
|---|---|---|
| Dextrose (D10–D70) | Provide 50–70% non-protein calories | Max GIR: 4–5 mg/kg/min (adults). Monitor glucose q4–6h initially |
| Amino Acids (AA) | 1.2–2.0 g/kg/day | Standard AA solutions. BCAA-enriched for hepatic encephalopathy |
| IV Lipid Emulsions (ILE) | 0.7–1.5 g/kg/day (provide 30–50% non-protein cal) | Max 1.5 g/kg/day. MCT/LCT or olive-oil based (SMOFlipid) preferred |
| Electrolytes | Na, K, Ca, Mg, PO₄ per labs | Watch PO₄ closely (refeeding). Ca:PO₄ ratio critical for stability |
| Trace Elements | Zn, Cu, Se, Mn, Cr | Reduce Mn in cholestasis; ↑ Zn in diarrhea/fistula/burns |
| Vitamins | MVI daily | Extra thiamine (B1) before dextrose in malnourished (prevent Wernicke's) |
PN Complications
CLABSI
Central line infection. Strict aseptic technique, dedicated PN lumen. Remove line if suspected.
Hyperglycemia
Limit dextrose GIR. Add insulin to PN bag or separate drip. Target 140–180 mg/dL.
Hypertriglyceridemia
Hold ILE if TG >400 mg/dL. Check weekly. Reduce lipid dose to 0.5g/kg/day.
PN-Associated Cholestasis
↑ Bilirubin, ↑ ALP. Cycle PN, reduce ILE, use fish-oil ILE (Omegaven). Start EN ASAP.
Refeeding Syndrome
↓PO₄, ↓K, ↓Mg. Start low, advance slowly. Pre-treat with thiamine 200–300mg IV.
Fluid Overload
Use concentrated formulas. Daily I/O balance. Limit total volume per fluid strategy.
Pediatric ICU Nutrition
📌 Key Guideline: ASPEN 2017 Pediatric Critical Care Nutrition
Children are NOT small adults. Higher metabolic rate per kg, limited glycogen/fat reserves, ongoing growth demands. Malnutrition prevalence in PICU: 24–50%.
Energy & Protein Requirements by Age
| Age Group | Energy (kcal/kg/day) | Protein (g/kg/day) | Fluid (mL/kg/day) |
|---|---|---|---|
| Preterm Neonate | 110–130 | 3.5–4.0 | 150–180 |
| Term Neonate (0–1 mo) | 90–120 | 2.5–3.0 | 120–150 |
| Infant (1–12 mo) | 70–100 | 2.0–3.0 | 100–120 |
| Toddler (1–3 yr) | 60–90 | 1.5–2.0 | Holliday-Segar |
| Child (3–10 yr) | 50–75 | 1.5–2.0 | Holliday-Segar |
| Adolescent (10–18 yr) | 30–55 | 1.5–2.0 | Holliday-Segar (max 2.4L) |
Pediatric Enteral Formulas
Infants (<1 year)
- • Breast milk (preferred) – add HMF for preterm
- • Standard infant formula (20 kcal/oz)
- • Concentrated to 24–30 kcal/oz if fluid-restricted
- • Extensively hydrolyzed (Alimentum, Nutramigen) for CMPA
- • Amino acid-based (EleCare, Neocate) for severe allergy
Children (1–13 years)
- • Pediatric polymeric (PediaSure 1.0, Nutren Junior)
- • High-calorie (1.5 kcal/mL) for fluid restriction
- • Peptide-based (Peptamen Junior) for GI dysfunction
- • Blenderized diet via GT for long-term patients
- • Adult formulas acceptable for >10 yr / >40 kg
Neonatal & Pediatric PN Protocol
| Component | Start (Day 1) | Advance | Max |
|---|---|---|---|
| Amino Acids | 1.5–2.0 g/kg (neonate), 1.0 g/kg (child) | ↑ 0.5–1.0 g/kg/day | 3.5–4.0 (preterm), 2.0–3.0 (child) |
| Dextrose (GIR) | 4–6 mg/kg/min (neonate) | ↑ 1–2 mg/kg/min/day | 10–14 mg/kg/min (neonate), 5 (adolescent) |
| IV Lipid | 1.0 g/kg/day | ↑ 0.5–1.0 g/kg/day | 3.0 g/kg (preterm), 2.0–3.0 (child) |
| SMOFlipid/Omegaven | Preferred in PNALD. Fish oil reduces bilirubin. Dose: 1g/kg/day Omegaven for cholestasis rescue | ||
Pediatric-Specific Considerations
🫀 Congenital Heart Disease
↑ REE 30–50%. Fluid-restricted: use concentrated formulas. Post-surgical: EN within 6–24h if hemodynamically stable.
🧠 Traumatic Brain Injury
Hypermetabolic. Early EN <72h. Target full calories by Day 7. Avoid hyperglycemia. Zinc supplementation may help.
🔥 Pediatric Burns
Galveston formula: 1800 kcal/m² + 1300 kcal/m² burn. Protein 3g/kg/day. Start EN within 6h. Vitamin C, Zinc, Copper supplementation.
🫁 Pediatric ARDS/Ventilated
Use IC if available (Schofield equation if not). Avoid overfeeding (↑ CO₂ production). Fluid restriction may require calorie-dense formula.
Nutrition Monitoring Protocol
| Parameter | Frequency | Target / Interpretation |
|---|---|---|
| Blood Glucose | q4–6h initially, then q6–8h | 140–180 mg/dL. Avoid <70 and >250 |
| Electrolytes (Na, K, Cl, HCO₃) | Daily (initiation), then 2–3×/wk | Normal ranges. Adjust PN/IV fluids accordingly |
| Phosphate, Magnesium, Calcium | Daily × 3–5 days (refeeding risk), then 2×/wk | Critical for refeeding syndrome detection. Replace aggressively |
| Triglycerides | Baseline, then weekly (on ILE) | <400 mg/dL. Hold lipid if >400 |
| LFTs (AST, ALT, ALP, Bilirubin) | Baseline, then weekly on PN | Monitor for PN-associated liver disease |
| Prealbumin (Transthyretin) | Weekly | t½ = 2–3 days. Better marker than albumin. Rising = adequate nutrition |
| Nitrogen Balance | Weekly if feasible | N balance = (Protein intake/6.25) – (UUN + 4). Target positive balance |
| Weight | Daily | Interpret cautiously (fluid shifts). Dry weight trends more useful |
| GRV / Abdominal Exam | q4–6h (EN patients) | Do not routinely hold for GRV <500. Assess clinically |
Refeeding Syndrome – Prevention & Management
Risk Factors (NICE criteria):
- • BMI <16 kg/m²
- • Unintentional weight loss >15% in 3–6 months
- • Little/no intake for >10 days
- • Low PO₄, K, or Mg pre-feeding
- • Alcoholism, anorexia nervosa, cancer, post-bariatric
Management Protocol:
- • Thiamine 200–300mg IV BEFORE feeding × 3 days
- • Start at 10 kcal/kg/day (max 50% target)
- • Advance by 33% every 1–2 days if stable
- • Replace PO₄, K, Mg aggressively (IV preferred)
- • Monitor electrolytes q12h × 72 hours
- • Restrict Na; supplement micronutrients
Sepsis & Hemodynamic Instability
Contraindication to EN: Uncontrolled shock (rising lactate, escalating vasopressors ≥2, MAP <60 despite resuscitation).
Low-dose EN safe if: MAP stable on single vasopressor (norepinephrine ≤0.14 mcg/kg/min), resolving lactate, adequate resuscitation.
Approach: Trophic feeding (10–20 mL/hr) during acute resuscitation → advance once hemodynamics stabilize (24–48h). Monitor for bowel ischemia (abdominal distension, rising lactate with feeds, bloody stool).
Protein: 1.5–2.0 g/kg/day. Do not delay protein delivery.
ARDS & Mechanical Ventilation
Avoid overfeeding: Excess calories → ↑ CO₂ production → difficulty weaning. RQ >1.0 indicates overfeeding.
Prone positioning: EN can continue in prone position. Use continuous infusion, post-pyloric preferred. Hold 1–2h before proning if bolus.
Fluid strategy: Conservative fluid approach in ARDS. Use calorie-dense (1.5–2.0 kcal/mL) formula to minimize volume.
ECMO: EN is safe and preferred on ECMO. Start within 24h. Monitor for gut ischemia.
Acute Kidney Injury & CRRT
AKI without RRT: Protein 0.8–1.0 g/kg/day (do NOT restrict to prevent RRT initiation). Standard EN formula.
CRRT: Protein 2.0–2.5 g/kg/day (amino acid losses 10–15g/day via effluent). Full caloric support. Account for citrate calories (~500 kcal/day from regional anticoagulation).
Electrolytes: Restrict K, PO₄ only if persistently elevated despite RRT. Use renal-specific formula only if electrolyte derangements unmanageable.
Fluid: Volume-dense formulas. Account for CRRT fluid removal in overall fluid balance.
Acute Liver Failure / Cirrhosis
DO NOT restrict protein. Protein restriction does NOT improve hepatic encephalopathy (Level 1 evidence). Target 1.2–1.5 g/kg/day.
BCAA-enriched formulas: Only if documented protein intolerance (rare).
Energy: 25–35 kcal/kg dry BW/day. Use dry/ideal weight (ascites distorts actual weight).
Micronutrients: Thiamine, folate, zinc supplementation. Reduce manganese and copper in cholestasis.
Timing: Late evening snack (50g complex carbs) prevents overnight gluconeogenesis and muscle catabolism.
Acute Pancreatitis
Mild: Oral diet as tolerated (low-fat, soft). No need for NPO or "pancreatic rest."
Severe (necrosis, organ failure): EN within 24–48h via nasogastric (NG = NJ per meta-analyses). EN ↓ infection, ↓ mortality vs PN.
Formula: Polymeric formula is acceptable (no benefit of semi-elemental in RCTs). Start low, advance.
PN: Only if EN fails or contraindicated. If >Day 5 without EN achieving >60% target.
Major Burns (>20% TBSA)
Timing: EN within 4–6 hours of injury (↓ ileus, ↓ hypermetabolism, ↓ bacterial translocation).
Energy: Curreri formula: 25 kcal/kg + 40 kcal/%TBSA burn. Or Toronto formula (IC preferred). REE ↑ 40–100%.
Protein: 1.5–2.5 g/kg/day. High-protein formula essential.
Micronutrients: Vitamin C 1000mg/day, Zinc 220mg/day, Copper, Selenium. Oxandrolone in select patients. Glutamine debated.
Glycemic control: Insulin for target <150 mg/dL. Burns cause severe insulin resistance.
Post-Surgical / ERAS Protocol
ERAS (Enhanced Recovery After Surgery): Clear fluids up to 2h pre-op. Carbohydrate loading 12h and 2h pre-op. Oral intake Day 0 post-op.
GI surgery: Early EN (Day 1) via jejunostomy below anastomosis. No evidence to wait for bowel sounds, flatus, or BM.
Open abdomen: EN safe and recommended. Protein losses via peritoneal fluid (additional 2g/L measured).
Immunonutrition: Arginine + omega-3 + nucleotides perioperatively for major GI cancer surgery (↓ infections by 30%).