Nutritional Considerations for ICU Patients

Nutritional Considerations for ICU Patients

• Nutrition is crucial for optimizing outcomes and recovery in ICU patients. It's no longer just a support but a therapy.

Stages of Critical Illness

• Critical illness is divided into three phases: early acute (1-2 days), acute late (3-7 days), and recovery (>7 days).
• Early acute phase: initial stress response with increased metabolic rate, hyperglycemia, and insulin resistance, though energy expenditure is decreased.
• Acute late phase: hypercatabolic phase with increased metabolic rate, muscle protein breakdown, and ongoing inflammation, further increasing energy expenditure.
• Recovery phase: focuses on anabolic processes, tissue repair, and restoration of normal metabolic function.
• Defining specific time points is arbitrary without a reliable biomarker.

Nutritional Risk Assessment

• Malnutrition prevalence in ICU patients ranges from 38% to 78%.
• Malnutrition significantly impacts outcomes like hospital stay, mechanical ventilation duration, infection rates, and mortality.
• Nutritional risk is assessed using various tools including: NRS-2002, NUTRIC, modified-NUTRIC, SGA, and MUST.
• NRS-2002 and m-NUTRIC are superior at predicting clinical outcomes, focusing on both nutrition and disease severity.
• ESPEN recommends a thorough clinical assessment (including medical history, muscle mass/strength, weight loss, and body composition) for patients with an expected ICU stay greater than 48 hours or with ventilator support, severe infections, or chronic illnesses or undernutrition before admission.

Energy Requirements

• Indirect calorimetry (IC) is the gold standard for determining energy requirements.
• IC measures oxygen consumption (VO2) and carbon dioxide production (VCO2) to estimate resting metabolic rate and total energy expenditure.
• An alternative, the Fick method, relies on pulmonary artery catheterization (less practical).
• Weir's equation can calculate REE with or without nitrogen measurement (assuming nitrogen is inactive for calculation).

Macronutrients

• Water: 30mL/kg/day, accounting for intake via medications and nutrition.
• Electrolytes (Na+, K+, Cl-): specific daily recommendations exist.
• Carbohydrates: 45-60% of calorie needs, with a maximum recommendation of 5mg/kg/min.
• Protein: 0.8g/kg/day initially, potentially increasing to 2g/kg/day in some cases, given patient needs.
• Lipids: 1-1.5g/kg/day for intravenous use; 30%-40% of calorie needs. Propofol is a lipid-based energy source.

Micronutrients and Immunonutrition (INT)

• Measurement of plasma micronutrient levels in critically ill patients is unreliable.
• Maintenance doses of micronutrients are crucial.
• Most enteral formulations provide sufficient micronutrients for those consuming 1500kcal+ daily.
• INT aims to improve immune function, reduce inflammation, and support healing (includes glutamine, omega-3 fatty acids, arginine, and antioxidants).

Modes of Nutritional Support

• Oral feeding is the preferred method when feasible.
• Enteral nutrition (EN) is suitable for patients with intact gut function but unable to consume orally.
• Parenteral nutrition (PN) is used as a last resort for patients unable to tolerate oral or EN, delivered via peripheral intravenous (PPN) or central venous (CPN) access.
• PPN offers rapid nutritional intervention as it's easier to establish but has limited capabilities.
• CPN provides greater nutritional support for extended needs but involves higher risk.

When to Decide on Feeding Type

• A comprehensive clinical assessment determines nutritional risk.
• Oral feeding is initially prioritized.
• EN should be started within 48 hours.
• PN is considered only if EN is not workable as a last resort, especially in patients who are severely malnourished and tolerating EN is not possible.

Considerations for Specific Situations

• Aspiration risk: patients are fed in an upright position (35-40 degrees).
• Prokinetics: used to support gut function, primarily when symptoms of intolerance arise.