What are the guidelines for nutrition in the Intensive Care Unit (ICU)?

Nutrition in the ICU: Evidence-Based Guidelines

Initiation and Route of Nutrition

All ICU patients who are not expected to resume full oral diet within 3 days should receive enteral nutrition (EN), initiated within 24-48 hours of admission in hemodynamically stable patients with functioning gastrointestinal tracts. 1

Priority Algorithm for Route Selection:

1. Oral diet - Use if patient can eat and cover ≥70% of needs without aspiration risk 1
2. Enteral nutrition (EN) - First-line for all others; reduces infectious complications by 50% compared to parenteral nutrition (RR 0.50, CI 0.37-0.67) and shortens ICU stay by 0.73 days and hospital stay by 1.23 days 1, 2
3. Parenteral nutrition (PN) - Only when EN is contraindicated or fails to meet targets after 3-7 days 1

Gastric vs. Jejunal Feeding:

• Start with gastric feeding (nasogastric or orogastric) in most patients 1, 3
• No significant difference in efficacy between gastric and jejunal routes 1, 2
• Switch to post-pyloric/jejunal feeding only if gastric intolerance develops (high residuals, vomiting) or high aspiration risk 4, 3

Energy Targets: Biphasic Approach

Acute Phase (Days 1-3):

Limit energy delivery to 20-25 kcal/kg/day during the acute phase to avoid overfeeding, which is associated with worse outcomes. 1, 5

• Hypocaloric feeding (~70% of target) during early critical illness is not harmful and may be beneficial 1
• Avoid exceeding 25 kcal/kg/day in the first 72-96 hours 1
• Full nutrition support should NOT be provided before day 4-7 1, 4

Recovery/Anabolic Phase (After Day 4-7):

Increase energy targets to 25-30 kcal/kg/day during the recovery phase once patients stabilize. 1, 5

• Use indirect calorimetry to measure energy expenditure after stabilization for more accurate targets 1
• Progress feeding gradually over the first week 1, 6

Protein Delivery: Progressive Strategy

Start with low-dose protein (<0.8 g/kg/day) during days 1-2, then progress to ≥1.2 g/kg/day as patients stabilize. 1, 4

• During acute phase: Maximum 0.8 g/kg/day 1, 4
• During recovery/rehabilitation: Target >1.2 g/kg/day 1, 4
• Avoid higher protein doses in hemodynamically unstable patients and acute kidney injury without CRRT 1

Parenteral Nutrition: When and How

PN should be implemented within 3-7 days when EN is contraindicated or insufficient, but never as first-line therapy. 1, 5

Specific Indications for PN:

• EN contraindicated (bowel obstruction, discontinuity, severe intolerance) 1
• Severely malnourished patients who cannot receive EN 1, 2
• EN fails to meet nutritional targets after 3-7 days 1

PN Dosing:

• Provide approximately 50% of predicted energy needs when supplementing EN 1
• Avoid early full PN (within first 3-4 days) as it may be harmful 1
• Maintain blood glucose 4.5-10 mmol/L to prevent hyperglycemia-associated complications 5

Special Populations and Formulas

Sepsis and Septic Shock:

In septic patients, start low-dose EN early (within 24-48h) at 20-50% of full nutrition, then progress gradually based on hemodynamic stability and GI tolerance. 1

• Avoid full EN during septic shock with hemodynamic instability 1
• No mortality benefit from increased protein (1.2 g/kg/d) in septic patients 1

Immune-Modulating Formulas:

Standard polymeric formulas should be used routinely; immune-modulating formulas (arginine, nucleotides, omega-3 fatty acids) are NOT recommended for severe sepsis (APACHE II >15) and may be harmful. 1, 3

• Consider immune-modulating formulas only for: elective upper GI surgery, mild sepsis (APACHE II <15), trauma, or ARDS with omega-3/antioxidants 1
• Whole protein formulas are appropriate for most patients; no advantage of peptide-based formulas 1, 2

Glutamine Supplementation:

Glutamine should be supplemented only in burn and trauma patients. 1

Monitoring and Tolerance

Gastric Intolerance Management:

For high gastric residual volumes or vomiting, administer IV metoclopramide or erythromycin rather than stopping EN. 1, 4

• Vomiting and increased gastric residual volume indicate gastric intolerance 4
• Consider eliminating routine gastric residual volume checks to minimize feeding interruptions 3

Refeeding Syndrome Prevention:

Monitor plasma phosphate daily; a 30% drop indicates refeeding syndrome and requires reduction of feeding rate plus high-dose thiamine. 4

• Particularly important in malnourished patients 2, 4
• Monitor electrolytes strictly when initiating nutrition 2

Critical Pitfalls to Avoid

• Delaying nutrition initiation beyond 48 hours in appropriate candidates 1, 2, 7
• Overfeeding during acute phase (>25 kcal/kg/day in first 3-4 days) is associated with worse outcomes 1
• Using PN as first-line when EN is feasible; this increases infectious complications 1, 2
• Stopping EN prematurely for high gastric residuals without attempting prokinetic agents 1, 2
• Ignoring cumulative energy deficit beyond 10,000 kcal, which increases complications 1
• Failing to progress nutrition after stabilization; patients often receive only partial targets 6, 3

Implementation Strategies

Establish nurse-driven feeding protocols with volume-based or "top-down" feeding strategies to enhance adequacy of nutrition delivery. 3

• Protocolized nutritional support improves EN supply and may reduce mortality 7
• Computerized nutrition monitoring systems should be utilized 1
• Regular audits of delivered vs. prescribed nutrition are essential 6