What are the nutritional guidelines for critically ill patients in the Intensive Care Unit (ICU)?

Nutritional Guidelines in the ICU

Primary Recommendation

Initiate enteral nutrition (EN) within 24-48 hours of ICU admission in hemodynamically stable critically ill patients with a functioning gastrointestinal tract, as this is the preferred route over parenteral nutrition and reduces infectious complications by 50%. 1, 2

Route Selection Algorithm

First-Line: Oral Diet

• Oral feeding should be the first choice if the patient can safely swallow and meet ≥70% of nutritional needs by days 3-7 without aspiration risk. 1

Second-Line: Enteral Nutrition (EN)

• Start EN within 24-48 hours if oral intake is inadequate or unsafe. 1, 2
• EN reduces infectious complications (RR 0.50,95% CI 0.37-0.67), shortens ICU stay by 0.73 days, and hospital stay by 1.23 days compared to early parenteral nutrition. 1, 2
• No significant difference exists between gastric versus jejunal feeding routes in most ICU patients. 1, 2

Third-Line: Parenteral Nutrition (PN)

• If EN is contraindicated or not feasible, initiate PN within 3-7 days after ICU admission. 1, 3
• Exception: In severely malnourished patients, early progressive PN can be started earlier when EN is contraindicated. 1, 3
• Recent evidence suggests PN can be given safely with similar outcomes to EN when early EN is not feasible, though EN remains preferred. 1

Energy and Protein Targets

Acute Phase (First 3-7 Days)

• Provide 20-25 kcal/kg/day during the acute phase to avoid overfeeding, which is associated with worse outcomes. 1, 3, 4
• Start with low-dose protein (<0.8 g/kg/day) and progress gradually. 1
• Target approximately 70% of measured energy expenditure during early phase. 1

Recovery/Anabolic Phase (After Day 7)

• Increase energy provision to 25-30 kcal/kg/day once patients stabilize. 1, 4
• Advance protein to ≥1.2 g/kg/day, ideally 1.3-1.5 g/kg ideal body weight/day. 1, 3, 4

Critical Caveat on Protein

• Avoid higher protein doses in hemodynamically unstable patients and those with acute kidney injury not receiving continuous renal replacement therapy (CRRT). 1

Energy Expenditure Measurement

Use indirect calorimetry (IC) to measure actual energy expenditure after patient stabilization post-ICU admission, as recommended by both American and European guidelines. 1

Progression Strategy

• Start EN at low rates and increase slowly over 3-7 days to avoid overfeeding. 1, 2
• Early full EN or PN should NOT be used—gradual progression over 3-7 days is essential to prevent complications. 1
• Monitor feeding tolerance, particularly gastric residual volumes. 2

Managing Feeding Intolerance

Administer intravenous metoclopramide or erythromycin for patients with high gastric residuals before abandoning EN. 1, 2

Supplemental Parenteral Nutrition

Add supplemental PN only if EN fails to meet nutritional targets after 3-7 days, particularly in severely malnourished patients. 1, 2

Specialized Formulas

Standard Approach

• Whole protein formulas are appropriate for most ICU patients—peptide-based formulas show no clinical advantage. 1, 2

Immune-Modulating Formulas

• Do NOT use immune-modulating formulas (arginine, nucleotides, omega-3 fatty acids) in patients with severe sepsis or APACHE II score >15, as they may be harmful. 1
• Consider immune-modulating formulas only in mild sepsis (APACHE II <15) or ARDS patients (omega-3 fatty acids with antioxidants). 1

Glutamine Supplementation

• Supplement glutamine in burn and trauma patients. 1

Glucose Management

Maintain blood glucose between 4.5-10 mmol/L (approximately 80-180 mg/dL), as hyperglycemia significantly increases mortality and infectious complications. 3, 4

Micronutrient Monitoring

In patients at risk for micronutrient losses (especially those on CRRT), evaluate micronutrient levels after ICU days 5-7 and replete deficiencies as indicated. 1

Nutrition Risk Screening

Screen patients using validated tools like NRS-2002, prioritizing those staying >2 days in ICU, requiring mechanical ventilation, infected, underfed >5 days, or with severe chronic disease. 1

Critical Pitfalls to Avoid

Overfeeding in Acute Phase

• Providing >25 kcal/kg/day during the first week is associated with worse outcomes and increased infectious complications. 1, 2

Delayed Nutrition Initiation

• All ICU patients not expected to resume full oral diet within 3 days should receive nutrition support—delays worsen outcomes. 1, 2

Premature PN Use

• Do not start PN before attempting EN in patients with functioning GI tracts, as EN significantly reduces infectious complications. 1, 2

Abandoning EN Prematurely

• High gastric residuals should prompt prokinetic intervention, not abandonment of EN. 2

Refeeding Syndrome

• Strictly monitor electrolytes and phosphorus when initiating nutrition in malnourished patients to prevent refeeding syndrome. 2

Monitoring Platforms

Utilize computerized nutrition monitoring systems to track delivered energy and protein as percentage of targets, as these platforms have become widely available. 1

Emerging Considerations

Future practice may incorporate muscle ultrasound, CT scan, or bioelectrical impedance analysis (BIA) to assess nutrition risk and monitor response to therapy. 1