Protein Management in Acute Kidney Injury
No, protein should NOT be avoided in AKI—in fact, protein restriction is explicitly contraindicated and adequate to high protein intake is essential to prevent negative nitrogen balance, muscle wasting, and mortality. 1, 2
Core Principle: Avoid Protein Restriction
The KDOQI Work Group explicitly recommends avoiding restriction of protein intake with the aim of preventing or delaying initiation of renal replacement therapy (RRT). 1 This represents a fundamental shift from outdated practices that restricted protein to manage azotemia. The rationale is clear: protein provision is intended to avoid marked net negative nitrogen balance, which worsens outcomes and mortality. 1
Specific Protein Targets by Clinical Status
Non-Dialysis AKI (Noncatabolic Patients)
- Provide 0.8-1.0 g/kg/day of protein using pre-hospitalization or usual body weight, not actual body weight 1, 2
- This baseline target prevents protein-energy wasting while avoiding excessive azotemia 2
Critically Ill AKI (Not on Dialysis)
- Start with 1.0 g/kg/day and gradually increase up to 1.3 g/kg/day if tolerated 2, 3
- The catabolic state of critical illness fundamentally changes protein requirements upward 2
AKI on Intermittent Hemodialysis
- Provide 1.0-1.5 g/kg/day of protein 1
- Additional protein is required because amino acids are removed during dialysis sessions 1, 2
AKI on Continuous Renal Replacement Therapy (CRRT)
- Provide 1.5-1.7 g/kg/day, with some evidence supporting up to 2.0-2.5 g/kg/day 2, 3
- CRRT causes continuous amino acid losses requiring the highest protein supplementation 1, 2
Hypercatabolic Patients
- Provide up to 1.7 g/kg/day regardless of RRT status 1
- Hypercatabolic states (sepsis, burns, trauma) require additional protein to avoid net negative nitrogen balance 1
Critical Pitfalls to Avoid
Do not restrict protein to manage rising BUN—azotemia should be managed with appropriate RRT dosing, not protein restriction. 2 This outdated practice worsens nutritional status and outcomes.
Do not use actual body weight for calculations—this overestimates protein requirements in patients on RRT and underestimates needs in those not on dialysis. 2 Always use pre-hospitalization or usual body weight.
Do not continue outpatient CKD protein restrictions during acute illness—the catabolic state of AKI fundamentally changes protein requirements, making chronic kidney disease restrictions inappropriate and harmful. 2
Route of Delivery
Provide nutrition preferentially by the enteral route. 1 Early parenteral nutrition in critically ill patients is associated with higher complication rates, primarily infectious complications. 1 However, parenteral nutrition should be initiated when >60% of energy and protein requirements cannot be met enterally within 7-10 days. 3
Consider concentrated renal formulas (70-80 g protein/L) to reduce fluid overload while meeting protein targets. 2
Monitoring Strategy
Calculate protein catabolic rate when feasible, especially in patients on RRT, as normalized protein catabolic rates in AKI patients on RRT range from 1.2-2.1 g/kg/day. 2 This provides more accurate assessment than body weight-based estimates alone.
Monitor nitrogen balance to guide protein dosing adjustments. 2 Assess for micronutrient deficiencies (selenium, zinc, copper) which increase during RRT. 2
Pediatric Considerations
Children have higher protein requirements due to developmental growth: 2-3 g/kg/day for ages 0-2 years, 1.5-2.0 g/kg/day for ages 2-13 years, and 1.5 g/kg/day for adolescents 13-18 years. 1 Children requiring RRT need supplementation beyond these baseline requirements. 1