Nutrition Guidelines for Critically Ill Mechanically Ventilated COVID19 Patients

Severe COVID19 frequently leads to acute respiratory distress syndrome (ARDS) requiring invasive mechanical ventilation. In this setting, metabolic demands are markedly altered and nutrition becomes a cornerstone of supportive care. The following guidelines synthesize current evidence and expert consensus to help clinicians provide optimal nutritional support to this vulnerable population.

1. General Principles

• Early initiation: Start feeding within 2448hours of ICU admission whenever hemodynamically stable.
• Goaldirected therapy: Tailor energy and protein targets to disease severity, body composition and metabolic response.
• Enteral nutrition (EN) preferred: Use the gastrointestinal tract whenever possible; switch to parenteral nutrition (PN) only if EN is contraindicated or fails to meet >60% of targets after 3days.
• Avoid overfeeding: Hyperglycemia, excess CO production and hepatic steatosis worsen outcomes.

2. Energy Requirements

Energy needs in ventilated COVID19 patients are highly variable. The following approach balances accuracy and practicality:

1. Calculate predicted energy using 2530kcalkgday (adjust for BMI: 30kcalkgday if BMI<25kg/m, 2225kcalkgday if BMI30kg/m).
2. If indirect calorimetry (IC) is available, measure resting energy expenditure (REE) within the first 48h and adjust targets accordingly.
3. Target 7080% of predicted/IC-derived calories for the first 3days (hypocaloric phase) and progress to 100% by day57.

3. Protein Provision

Protein catabolism is accelerated in critical illness and contributes to muscle wasting, prolonged ventilation and delayed recovery.

• Provide 1.22.0gkgday of protein (adjust for renal function; consider 1.5gkgday for obese patients using adjusted body weight).
• Distribute protein evenly across 46 feeding boluses or continuous infusion to maximize nitrogen balance.

4. Route of Feeding

4.1. Enteral Nutrition

EN is safe and feasible in >80% of mechanically ventilated COVID19 patients.

• Formulation: Begin with a standard polymeric formula (1.01.5kcalml) unless contraindicated.
• Feeding protocol: Start at 1020mlh and increase by 1020mlh every 46h as tolerated.
• GRV monitoring: Check every 4h; pause feeding if GRV>250ml and resume at a slower rate after measures (prokinetics, headofbed elevation).

4.2. Parenteral Nutrition

Use PN only when EN cannot meet >60% of energy/protein goals after 72h or when gastrointestinal contraindications exist (e.g., bowel ischemia, highoutput fistula).

• Start with a peripheral PN (PPN) formulation if caloric needs are modest; transition to central PN for full nutrition.
• Include electrolytes, trace elements and vitamins (especially vitaminD, C, thiamine) to avoid deficiencies.

5. Micronutrients and Immunomodulation

Critically ill COVID19 patients commonly exhibit deficiencies that may affect immune response and organ function.

6. Glycemic Control

Hyperglycemia is linked to higher mortality in COVID19 ICU patients.

• Target blood glucose 140180mg/dL (7.810mmol/L).
• Use insulin infusion protocols; avoid sliding scale alone.
• Prefer carbohydratecontrolled formulas (45% of total calories from carbs).

7. Fluid Management

Overhydration worsens pulmonary edema and impedes weaning.

• Deliver nutrition in a concentrated form (1.5kcalml) when fluid restriction <30mlkgday is required.
• Monitor cumulative fluid balance daily; adjust EN volume accordingly.

8. Monitoring and Adjustment

Regular assessment ensures that nutritional therapy remains safe and effective.

1. Daily: Energy & protein delivery, GRVs, electrolytes, glucose, nitrogen balance.
2. Every 35days: Remeasure REE with IC if available; adjust targets.
3. Weekly: Weight, midarm circumference, prealbumin (as trend, not absolute), liver function tests.

9. Special Situations

9.1. Prone Positioning

Proning is common in severe ARDS. EN can be continued safely with the following precautions:

• Elevate head of bed to 3040 when possible.
• Check GRVs before proning; if high, hold feed for 12h after repositioning.
• Consider postpyloric feeding to reduce aspiration risk.

9.2. Renal Replacement Therapy (RRT)

Continuous RRT increases protein losses.

• Increase protein provision by 0.20.3gkgday.
• Monitor urea nitrogen and adjust energy accordingly.

9.3. Obesity

Obese patients have higher VCO production and may require lower calorie density to avoid overfeeding.

• Use adjusted body weight for calculations.
• Target 1114kcalkgday (adjusted) and 2.02.5gkgday protein.

10. Summary Checklist

• Initiate EN within 2448h if hemodynamically stable.
• Set energy goal 2530kcalkgday (adjust with IC).
• Provide 1.22.0gkgday protein.
• Monitor GRVs, glucose, electrolytes daily.
• Add vitaminD, C, thiamine, selenium as per protocol.
• Reevaluate nutrition goals every 35days.
• Switch to PN only after EN failure >72h.

Adhering to these evidencebased recommendations helps preserve lean body mass, modulate the inflammatory response, and may shorten mechanical ventilation duration in critically ill COVID19 patients.