Nutrition in Critical Illness

Nutritional Assessment - Sizing Up Situation

• Goal: ICU nutrition ↓morbidity, ↓mortality, ↓LOS.
• Key Tools:
  • SGA (Subjective Global Assessment): Subjective.
  • NRS-2002 (Nutritional Risk Screening): Score ≥3 = risk.
  • NUTRIC Score: ICU-specific. Score 5-9 = high risk, benefit from nutrition.
• Limitations:
  • Biomarkers (Albumin, Prealbumin): Unreliable (APR, fluid shifts).
  • Anthropometry: Fluid shifts limit use in ICU.

⭐ NUTRIC score components: Age, APACHE II, SOFA, #Comorbidities, Days hosp to ICU, IL-6. Score ≥5 = high risk; consider aggressive nutrition therapy.

Caloric & Protein Needs - Fueling the Fight

• Energy Target: 20-25 kcal/kg/day.
  • Use actual body weight (ABW) for non-obese; adjusted BW for obese.
  • Gold Standard: Indirect calorimetry (IC).
  • Predictive equations (e.g., Harris-Benedict, Penn State) have limitations.
• Protein: 1.2-2.0 g/kg/day (↑ burns, trauma).

  ⭐ Protein target for most critically ill patients: 1.2-2.0 g/kg/day.

• Carbs: 50-70% non-protein calories; $GIR_{max}$ 4-5 mg/kg/min.
• Fats: 30-50% non-protein calories.

Enteral Nutrition - Gut Instincts First

• Indications: Functional GIT, inadequate oral intake.
• Contraindications: Ileus, obstruction, severe shock, high-output fistula (distal).
• Timing: Early EN (within 24-48 hours).

  ⭐ Early EN (within 24-48h) preserves gut integrity, ↓bacterial translocation & sepsis.

• Access Routes:
  • NG/NJ: Short-term; NG (↑aspiration), NJ (↓aspiration).
  • PEG/PEJ: Long-term; PEG (gastric), PEJ (jejunal, ↓aspiration).
• Formulas: Standard polymeric, fiber, high-protein.
• Initiation: Start 10-20 mL/hr, advance to goal.
• Complications:
  • GI: Diarrhea, GRV > 500ml (hold EN).
  • Mechanical: Tube issues.
  • Metabolic: Refeeding syndrome.

Parenteral Nutrition - Vein Victory Plan

• Indications: Non-functional GIT; EN contraindicated; EN failure to meet needs.
• Timing:
  • No EN: Start after 7 days (well-nourished), earlier (malnourished).
  • Supplemental PN: If EN <60% needs by day 7-10.
• Access:
  • Central (TPN): Preferred, high osmolarity.
  • Peripheral (PPN): Short-term, osmolarity <900 mOsm/L.
• Components: Dextrose, amino acids, lipid emulsions, electrolytes, vitamins, trace elements.
• Complications: Catheter-related (infection, thrombosis); metabolic (hyperglycemia, refeeding, PNALD); overfeeding.

⭐ Major risk with PN: Catheter-Related Bloodstream Infection (CRBSI).

Special Considerations - Tricky Patient Tactics

• Immunonutrition: Arginine, glutamine, omega-3 FAs; controversial.
• Sepsis: Early EN; avoid overfeeding.
• ARDS: Consider omega-3 FAs/antioxidants (limited evidence).
• Pancreatitis (Severe): Early EN (NJ preferred).
• Obesity: Hypocaloric, high-protein: 11-14 kcal/kg actual weight. Protein: >2.0 g/kg IBW (BMI 30-40), >2.5 g/kg IBW (BMI >40).

  ⭐ Protein for BMI >40: >2.5 g/kg IBW.

Monitoring & Pitfalls - Watching for Trouble

• Adequacy: Clinical signs, nitrogen balance (limited), indirect calorimetry (measures energy expenditure).
• Complications: Monitor glucose (target 140-180 mg/dL), electrolytes (K, Mg, PO₄), LFTs, triglycerides.
• Refeeding Syndrome (RFS):
  • Patho: Insulin surge → intracellular electrolyte shifts. 📌 PIMP: ↓Phosphate, ↓Potassium, ↓Magnesium.
  • Risks: Malnutrition, alcoholism. Prevent: Thiamine, slow refeed. Manage: Correct electrolytes.
  • ⭐ > Key electrolyte abnormalities in refeeding syndrome are hypophosphatemia, hypokalemia, and hypomagnesemia.
  • 

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Start["📋 At-Risk Patient?
• Identify risk level• Prepare nutrition"]

Nutrition{"💊 Start Nutrition
• Initiate feeding• Assess tolerance"}

LowRisk["✅ Low Risk
• Start 75% target• Ongoing monitoring"]

HighRisk["⚠️ High Risk
• Give Thiamine• 5-10 kcal/kg/day"]

Monitor["🔬 Lab Monitor
• PO4, K, Mg levels• Close observation"]

Correct["🚨 Electrolytes ⬇️
• Correct labs• Slow/Pause feed"]

Gradual["👁️ Monitoring
• Gradual ⬆️ Feed• Goal achievement"]

Start --> Nutrition Nutrition -->|No| LowRisk Nutrition -->|Yes| HighRisk HighRisk --> Monitor Monitor -->|Stable| Gradual Monitor -->|⬇️ Electrolytes| Correct Correct --> Gradual

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*   **Overfeeding:** Hyperglycemia, hepatic steatosis, ↑$CO_2$ production (difficult weaning).

##  High‑Yield Points - ⚡ Biggest Takeaways
> * **Early Enteral Nutrition (EEN)** within **24-48 hours** is preferred in critical illness.
> * Use **Parenteral Nutrition (PN)** if EN contraindicated or inadequate by day **7**.
> * Caloric goal: **25-30 kcal/kg/day**; Protein: **1.2-2.0 g/kg/day**.
> * Watch for **Refeeding Syndrome**: monitor **K, PO4, Mg**; give **thiamine** pre-feeding.
> * **Immunonutrition** (arginine, glutamine) has specific roles, not for routine sepsis.
> * High **Gastric Residual Volumes (GRVs)** alone don't mandate stopping EN.