What are the recommendations for protein supplement use in patients with Acute Kidney Injury (AKI)?

Protein Supplementation in Acute Kidney Injury

Protein supplementation should NOT be restricted in patients with AKI, and adequate to high protein intake is essential to prevent muscle wasting and improve survival, with specific targets based on illness severity and renal replacement therapy status. 1

Core Principle: Do Not Restrict Protein to Delay Dialysis

Protein prescription shall not be reduced to avoid or delay kidney replacement therapy (KRT) initiation in critically ill patients with AKI. 1 This is a Grade A recommendation with 96% consensus. The rationale is clear: lowering protein intake does not influence the protein catabolic rate in AKI patients, meaning restriction provides no metabolic benefit while potentially worsening nitrogen balance and muscle wasting. 1

Protein Targets Based on Clinical Status

Non-Critically Ill AKI Patients (Not on Dialysis)

• Target: 0.8-1.0 g/kg body weight/day 1
• This applies to hospitalized AKI patients without acute/critical illness
• Use pre-hospitalization or usual body weight, NOT actual body weight (which may be inflated by fluid overload) 1

Critically Ill AKI Patients (Not on Dialysis)

• Start with 1.0 g/kg/day and gradually increase up to 1.3 g/kg/day if tolerated 1
• This gradual escalation approach balances the need for adequate protein against metabolic tolerance
• The catabolic state of critical illness drives these higher requirements 1

AKI Patients on Intermittent Hemodialysis

• Target: 1.3-1.5 g/kg/day 1
• Higher requirements reflect amino acid losses during dialysis sessions
• Patients are often highly catabolic, requiring aggressive protein repletion 2, 3

AKI Patients on Continuous Renal Replacement Therapy (CRRT)

• Target: 1.5-1.7 g/kg/day 1
• CRRT causes substantial amino acid losses (approximately 25 g nitrogen/day) 1
• Some evidence suggests targets up to 2.0-2.5 g/kg/day may be beneficial for achieving positive nitrogen balance, though this increases urea production and may require higher CRRT doses 1
• A positive nitrogen balance is associated with improved survival in critically ill AKI patients 1

Practical Implementation Strategies

Preferred Method: Protein Catabolic Rate Monitoring

Protein prescription should ideally be guided by protein catabolic rate rather than body weight-based estimates alone. 1 Normalized protein catabolic rates in AKI patients on KRT range from 1.2-2.1 g/kg/day, reflecting the wide variability in catabolism. 1 This individualized approach is more accurate than fixed formulas, though it requires 24-hour urine and dialysate collection. 1

Delivery Route Considerations

• Enteral nutrition is preferred when possible 1, 3, 4
• Standard enteral formulas contain only 40-60 g protein/L, which may be insufficient 1
• Consider concentrated renal formulas (70-80 g protein/L) to reduce fluid overload while meeting protein targets 1
• Parenteral amino acid supplementation may be necessary when enteral route cannot meet >60% of protein requirements 1, 4

Avoid Overfeeding

Overfeeding should be avoided to achieve positive nitrogen balance. 1 Studies show that excessive caloric intake (40-60 kcal/kg/day) actually increases protein catabolism and worsens nitrogen balance. 1 The optimal energy target is 25-30 kcal/kg/day, with protein provision being the priority. 1, 2, 4

Critical Pitfalls to Avoid

Pitfall #1: Using Actual Body Weight

Critically ill AKI patients frequently have significant fluid overload. 1 Using actual body weight overestimates protein requirements in patients on KRT while underestimating needs in those not on dialysis. 1 Always use pre-hospitalization or usual body weight for calculations. 1

Pitfall #2: Continuing Outpatient Protein Restriction

CKD patients previously on low-protein diets should NOT continue this restriction during hospitalization for acute illness. 1 The catabolic state of acute illness fundamentally changes protein requirements, and continuing restriction will worsen outcomes. 1

Pitfall #3: Restricting Protein Due to Rising BUN

While high protein intake does elevate blood urea nitrogen, this is not a reason to restrict protein in catabolic AKI patients. 1 The accumulation of nitrogenous waste products should be managed with appropriate KRT dosing, not protein restriction. 1

Pitfall #4: Delaying Adequate Nutrition

Early enteral nutrition is recommended for critically ill AKI patients, with parenteral supplementation added within 7-10 days if enteral route cannot meet 60% of requirements. 4 Delayed nutrition support worsens protein-energy wasting, which occurs in up to 42% of ICU patients with AKI and is associated with increased mortality. 5

Exception: Metabolically Stable, Non-Catabolic AKI

A conservative approach with moderately restricted protein (0.6-0.8 g/kg/day) may be considered ONLY in metabolically stable patients with isolated AKI (e.g., contrast-induced, drug-induced, post-renal obstruction) who are NOT critically ill and NOT on dialysis. 1 This represents a small minority of hospitalized AKI patients. In any catabolic state, protein restriction worsens nitrogen balance and outcomes. 1

Monitoring Requirements

• Calculate protein catabolic rate when feasible, especially in patients on KRT 1
• Monitor nitrogen balance to guide protein dosing adjustments 1
• Track serum albumin and nutritional markers, recognizing that low BMI (<18.5 kg/m²) is associated with higher mortality 4
• Assess for micronutrient deficiencies (selenium, zinc, copper) which are increased during KRT 1
• Monitor for metabolic complications including hyperglycemia, hypertriglyceridemia, and electrolyte disturbances 2, 3