Nutrition in Critical Illness

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Nutrition in Critical Illness: Metabolic Response & Assessment - Stress & Status

  • Metabolic Response to Stress:
    • Hypermetabolism & severe catabolism.
    • ↑ Cortisol, glucagon, catecholamines; insulin resistance.
    • Cytokines (TNF-α, IL-1, IL-6) mediate.
    • Phases:
      • Ebb (24-48h): Hypometabolism. Goal: Resuscitation.
      • Flow: Hypermetabolism, ↑ catabolism, ↑ energy needs.
  • Nutritional Status Assessment:
    • Clinical: Weight loss Hx, muscle wasting.
    • Biochemical:
      • Serum proteins (albumin, prealbumin): ↓ by inflammation, unreliable alone.
      • Nitrogen balance: $N_{balance} = (Protein_{intake}/6.25) - (UUN + 4)$. Aim positive.
    • Energy Expenditure:
      • Predictive equations: Often inaccurate.
      • RQ = $VCO_2 / VO_2$.
        • RQ: ~0.7 fat, ~0.8 protein, ~1.0 carb; >1.0 overfeeding. Metabolic response phases in critical illness

⭐ Indirect calorimetry is the gold standard for determining energy expenditure in ICU patients, when available.

Nutrition in Critical Illness: Enteral Nutrition - Gut First Feeds

⭐ Early enteral nutrition (initiated within 24-48 hours of ICU admission) is preferred over delayed EN or parenteral nutrition in critically ill patients who can tolerate it.

  • Principle: "If the gut works, use it!" - preserves gut mucosal barrier, prevents bacterial translocation.
  • Timing: Initiate early, within 24-48h of ICU admission, if hemodynamically stable.
  • Benefits: ↓ septic complications, ↓ MODS, ↓ ICU stay, cost-effective.
  • Access Routes: Nasogastric (NG)/nasojejunal (NJ) short-term; PEG/PEJ for prolonged needs.
  • Monitoring Tolerance:
    • Clinical: Abdominal distension, pain, bowel sounds, stool.
    • GRV: Check q4-6h; >500mL (or 200-500mL + symptoms) → hold, reassess, prokinetics.
  • Complications: Aspiration (HOB 30-45°), diarrhea, tube malposition/clogging.

Nutrition in Critical Illness: Parenteral Nutrition - Veinous Victuals

  • Parenteral Nutrition (PN): Intravenous administration of nutrients when the enteral route is contraindicated or insufficient.
  • Indications:
    • Non-functional GI tract (e.g., prolonged ileus, obstruction, severe shock, high-output fistula).
    • Inability to achieve >60% of energy/protein requirements via EN by day 7-10.

    ⭐ If enteral nutrition is not feasible or sufficient, parenteral nutrition should be considered cautiously, typically after 7-10 days in patients at low nutritional risk, to avoid overfeeding and complications.

  • Timing of Initiation:
    • Low nutritional risk: Consider if EN not feasible/sufficient by day 7-10.
    • High nutritional risk or severe malnutrition: Initiate early (within 24-48 hours) if EN is not possible.
  • Access & Solutions:
    • Total PN (TPN): Via central venous catheter; allows hyperosmolar solutions for long-term needs.
    • Peripheral PN (PPN): Via peripheral vein; osmolarity limit <900 mOsm/L; for short-term use (<2 weeks).
  • Major Complications:
    • Catheter-related: Infection (CRBSI), thrombosis, pneumothorax.
    • Metabolic: Hyperglycemia, refeeding syndrome, electrolyte disturbances, PN-Associated Liver Disease (PNALD). Central venous line insertion and care
  • Monitoring: Blood glucose, electrolytes, LFTs, triglycerides.

Nutrition in Critical Illness: Monitoring & Complications - Watchful & Wise

  • Vigilant Monitoring:
    • Clinical: GI tolerance (N/V/D), fluid status.
    • Biochemical: Glucose (target 140-180 mg/dL), electrolytes (PO4, K, Mg - daily if risk), TGs.
  • Potential Complications:
    • Refeeding Syndrome: ⚠️ Severe ↓PO4, ↓K, ↓Mg (📌 P K Mg: Phosphate, Kalium, Magnesium). Risk in severely malnourished.
      • Initiate feeding low, advance slowly.
    • Overfeeding: Hyperglycemia, ↑CO2 production, hepatic steatosis.
    • Underfeeding: Weakness, poor healing, ↑infection risk.
    • GI intolerance: Diarrhea, high GRV.

⭐ Refeeding syndrome, characterized by severe hypophosphatemia, hypokalemia, and hypomagnesemia, is a critical complication to monitor for when initiating nutrition in severely malnourished patients.

High‑Yield Points - ⚡ Biggest Takeaways

  • Early Enteral Nutrition (EN) within 24-48 hours is superior to Parenteral Nutrition (PN).
  • Target calories: 25-30 kcal/kg/day; Target protein: 1.2-2.0 g/kg/day.
  • Immunonutrition (e.g., arginine, glutamine) benefits select critically ill patients.
  • Prevent Refeeding Syndrome: monitor for hypophosphatemia, hypokalemia, hypomagnesemia.
  • Permissive underfeeding or trophic feeding is often an initial strategy.
  • Gastric Residual Volume (GRV) monitoring is de-emphasized; focus on clinical intolerance.

Practice Questions: Nutrition in Critical Illness

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Flashcards: Nutrition in Critical Illness

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A patient in sepsis, DIC, ARDS would be classified under ASA _____

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A patient in sepsis, DIC, ARDS would be classified under ASA _____

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