What nutritional supplements are recommended for a patient with Acute Kidney Injury (AKI)?

Nutritional Supplementation in Acute Kidney Injury

Patients with AKI require supplementation of trace elements (selenium, zinc, copper) and water-soluble vitamins (thiamine, vitamin C, folate), with increased attention to these losses if undergoing kidney replacement therapy, while avoiding high-dose glutamine and using renal-specific rather than standard multivitamins. 1

Trace Element Supplementation

Monitor and supplement trace elements due to increased requirements during critical illness and large losses during kidney replacement therapy (KRT). 1

Priority Trace Elements:

• Selenium and Zinc: Serum levels decrease significantly during continuous KRT (CKRT) due to increased utilization in critical illness and dialysis losses 1. Standard supplementation of 50 mg/day zinc and 75 mg/day selenium may not correct deficiencies in patients on chronic KRT, suggesting even higher requirements 1

• Copper: Large effluent losses during CKRT far exceed nutritional intakes 1. When CKRT is required for more than 2 weeks, measure blood copper levels and consider intravenous administration of approximately 3 mg/day to prevent deficiency 1

Water-Soluble Vitamin Supplementation

Water-soluble vitamins should be monitored and supplemented, with special attention to vitamin C, folate, and thiamine. 1

Specific Vitamin Requirements:

• Thiamine (B1): Daily losses during dialysis are approximately 4 mg/day, with deficiency documented in 24.7% of hemodialysis patients 1, 2. Patients on CKRT may require 100-300 mg/day 2

• Vitamin C: Daily effluent losses are approximately 68 mg 1. Supplement at least 90 mg/day for men and 75 mg/day for women, but do not greatly exceed these amounts due to oxalate accumulation risk 2

• Folate: Daily losses during dialysis are approximately 0.3 mg 1

• Vitamin B6: Deficiency documented in 35.1% of hemodialysis patients 1, 2

Renal-Specific vs. Standard Multivitamins

Use renal-specific multivitamins rather than standard multivitamins in AKI patients, particularly those on dialysis. 2

Critical Differences:

• Renal vitamins contain lower or absent fat-soluble vitamins (A, E, K) to prevent toxicity, while providing adequate water-soluble vitamins to replace dialysis losses 2

• Vitamin A accumulates to toxic levels in kidney disease because retinol-binding protein is normally catabolized in renal tubules; standard multivitamins containing vitamin A pose significant toxicity risk and should be avoided 2

• Renal formulas have lower electrolyte content (sodium, potassium, phosphorus) to prevent hyperkalemia and hyperphosphatemia 2

• Vitamin K is typically excluded from renal vitamins, which is particularly important for patients on anticoagulants like warfarin 2

Protein and Amino Acid Supplementation

Enteral supplementation of amino acids is recommended to achieve protein goals, with patients on KRT requiring at least 1.5 g/kg/day plus an additional 0.2 g/kg/day to compensate for amino acid losses during dialysis. 1, 3, 4, 5

Important Caveats:

• Moderately restricted protein regimens may be considered ONLY in metabolically stable AKI patients without catabolic conditions and not undergoing KRT 1. This applies to selected non-catabolic conditions such as drug-induced isolated AKI or contrast-associated AKI 1

• When catabolic status exists, protein restriction invariably worsens nitrogen balance and is contraindicated 1

Supplements to AVOID

High-Dose Glutamine:

In critically ill patients with AKI, additional high-dose parenteral glutamine shall NOT be administered. 1

• The REDOX study demonstrated that high doses of intravenous or enteral alanyl-glutamine are harmful in the subgroup of critically ill patients with kidney failure 1

• This recommendation stands despite documented glutamine losses of approximately 1.2 g/day during CKRT 1

Omega-3 Fatty Acids:

There is insufficient evidence to support routine use of omega-3 PUFA supplements or parenteral nutrition solutions enriched with omega-3 in hospitalized AKI patients. 1

• No randomized controlled trials currently support their use in hospitalized patients with AKI, despite interesting experimental data 1

Electrolyte Monitoring

Electrolyte abnormalities are common in AKI patients receiving KRT and must be closely monitored. 1

Common Abnormalities with KRT:

• Hypophosphatemia (prevalence 60-80% in ICU) is associated with respiratory failure, cardiac arrhythmias, and prolonged hospitalization 1

• Hypokalemia and hypomagnesemia are common with intensive/prolonged KRT 1

• The initiation of KRT is a major risk factor for development of hypophosphatemia 1

Clinical Algorithm for Supplementation

1. Assess metabolic status: Determine if patient is catabolic or metabolically stable 1

2. If on KRT or anticipated KRT >2 weeks:

   • Initiate renal-specific multivitamin 2
   • Monitor and supplement selenium, zinc, copper 1
   • Ensure adequate water-soluble vitamins (thiamine, folate, vitamin C, B6) 1
   • Monitor copper levels if CKRT >2 weeks 1

3. Protein supplementation: Provide 1.5-1.7 g/kg/day if on KRT 1, 3, 4

4. Avoid: High-dose glutamine supplementation 1

5. Monitor electrolytes closely: Particularly phosphate, potassium, magnesium 1