How to optimize fluid balance, nutrition, and diet in Acute Kidney Injury (AKI)?

Optimizing Fluid Balance, Nutrition, and Diet in Acute Kidney Injury

In patients with Acute Kidney Injury (AKI), fluid management should be conservative after initial hemodynamic stabilization, with hypocaloric nutrition (not exceeding 70% of energy expenditure) in the early phase followed by gradual increase to 80-100% of requirements after day three, while providing adequate protein at 1.2-2.0 g/kg/day without restriction to avoid or delay kidney replacement therapy. 1

Fluid Management

Initial Approach

• Use isotonic crystalloids rather than colloids for initial expansion of intravascular volume in patients at risk for or with AKI 1
• After initial resuscitation, implement a conservative fluid strategy to avoid fluid overload, which is strongly associated with increased mortality in AKI 2
• Accurate fluid balance monitoring is essential - proper documentation of intake/output reduces AKI prevalence 3

Management of Fluid Overload

• Diuretics should not be used to prevent AKI but are appropriate for managing volume overload in established AKI 1, 4
• Higher furosemide doses may have a protective effect on mortality in AKI patients with fluid overload 2
• Consider early initiation of renal replacement therapy if conservative fluid management is insufficient to achieve neutral or negative fluid balance in severe fluid overload 1

Nutritional Support

Energy Requirements

• Provide hypocaloric nutrition (not exceeding 70% of energy expenditure) in the early phase of acute illness 1
• After day three, gradually increase caloric delivery to 80-100% of measured energy expenditure 1
• Avoid early full enteral or parenteral nutrition in critically ill patients with AKI; instead, prescribe full nutrition within 3-7 days 1
• If using predictive equations to estimate energy needs, maintain hypocaloric nutrition (below 70% estimated needs) for the first week of ICU stay 1

Protein Requirements

• Do not restrict protein intake to avoid or delay kidney replacement therapy initiation in critically ill patients with AKI 1
• Provide 1.2-2.0 g/kg/day of protein for catabolic AKI patients 5
• Increase to 1.5-2.5 g/kg/day for patients receiving continuous renal replacement therapy (CRRT) 5
• A conservative approach with moderately restricted protein (0.8-1.0 g/kg/day) may be considered only for metabolically stable, non-catabolic AKI patients not requiring kidney replacement therapy 1

Route of Administration

• Provide nutrition preferentially via the enteral route in patients with AKI 1
• Consider parenteral supplementation when >60% of energy and protein requirements cannot be met via the enteral route within 7-10 days 5
• More concentrated disease-specific (renal) enteral formulas containing 70-80 g of protein/L may be preferred to reduce fluid overload 1

Macronutrient Considerations

Carbohydrate and Lipid Balance

• Consider increasing lipid intake and reducing carbohydrate provision based on substrate utilization assessed by indirect calorimetry 1
• Patients with AKI may oxidize fewer carbohydrates and more lipids than expected 1
• Account for additional calories from citrate (3 kcal/g), glucose (3.4 kcal/g), and lactate (3.62 kcal/g) in dialysis/hemofiltration solutions to avoid overfeeding 1

Micronutrient Management

Trace Elements and Vitamins

• Monitor and supplement trace elements due to increased requirements during kidney failure and critical illness, and large effluent losses during kidney replacement therapy 1
• Pay particular attention to selenium, zinc, and copper levels 1
• Consider using kidney replacement therapy solutions enriched with phosphate, potassium, and magnesium to prevent electrolyte derangements 1

Monitoring Nutritional Status

Assessment Methods

• Use body composition assessment rather than anthropometry when diagnosing and monitoring malnutrition in AKI patients 1
• Consider ultrasound for assessment of muscle mass, as it is less influenced by fluid shifts compared to bioelectric impedance analysis 1
• Monitor handgrip strength in collaborative patients to assess muscle function 1
• Low BMI (<18.5 kg/m²) is associated with higher mortality in AKI patients 5

Special Considerations

Pre-existing Conditions

• CKD patients previously on controlled protein intake ("low protein diet") should not maintain this regimen during hospitalization if acute illness is the reason for admission 1
• Protein needs should be guided by the acute illness rather than the underlying CKD condition 1
• Avoid overfeeding in patients with AKI, as it may lead to increased metabolic complications (hyperglycemia, hypertriglyceridemia) and more positive fluid balance 1

Pitfalls to Avoid

• Do not use diuretics to prevent AKI as this may increase mortality 1, 4
• Avoid excessive fluid removal that could lead to hypovolemia and renal hypoperfusion 6
• Do not delay nutritional support in an attempt to prevent azotemia - inadequate protein intake may worsen nutritional status and lead to poorer outcomes 7
• Be cautious with bioelectric impedance analysis in fluid-overloaded patients as it provides inaccurate values of fat-free mass 1