What are the recommended amino acid supplementation guidelines for patients undergoing dialysis?

Amino Acid Supplementation in Dialysis Patients

For stable maintenance hemodialysis patients, aim for a total protein intake of 1.2 g/kg/day (at least 50% high biological value), and for peritoneal dialysis patients 1.2-1.3 g/kg/day, recognizing that dialysis removes 10-12 g of amino acids per hemodialysis session and approximately 3 g/day in peritoneal dialysis. 1

Protein and Amino Acid Requirements by Dialysis Modality

Maintenance Hemodialysis (MHD)

• Target protein intake: 1.2 g/kg/day minimum, with at least 50% from high biological value sources 1
• Each hemodialysis session removes approximately 10-12 g of amino acids, creating substantial ongoing losses that must be replaced 1
• More intensive dialysis schedules (>3 times weekly or continuous venovenous hemofiltration) may require protein intakes exceeding 1.2-1.3 g/kg/day due to increased amino acid removal 1
• Recent research confirms severe amino acid losses during high-efficiency hemodialysis and hemodiafiltration, with total losses of approximately 5 g per session (>65% of circulating amino acids) 2

Chronic Peritoneal Dialysis (CPD)

• Target protein intake: 1.2-1.3 g/kg/day, with at least 50% high biological value protein 1
• Peritoneal dialysis causes daily amino acid losses averaging 3 g/day, with protein losses of 5-15 g per 24 hours (higher during peritonitis) 1
• The higher protein requirement compared to normal individuals reflects these obligatory dialysate losses 1
• Nitrogen balance studies demonstrate that intakes of 1.2 g/kg/day or greater consistently achieve neutral or positive nitrogen balance 1

Acutely Ill Dialysis Patients

For hospitalized or acutely ill dialysis patients, increase protein intake to 1.2-1.3 g/kg/day minimum, with energy intake of 30-35 kcal/kg/day. 1

• Acutely ill dialysis patients typically ingest less than recommended amounts and remain in negative nitrogen balance 1
• Protein intakes ≥1.3 g/kg/day with non-protein energy of 34 kcal/kg/day improve biochemical nutritional markers in hospitalized patients 1
• While higher protein intakes (1.5-2.5 g/kg/day) are used in non-renal critically ill patients, these may not be tolerated in dialysis patients unless receiving more intensive dialysis due to increased water and mineral intake 1
• When oral intake is inadequate, tube feeding, intradialytic parenteral nutrition (IDPN), or total parenteral nutrition (TPN) should be initiated 1

Specific Amino Acid Supplementation Strategies

Amino Acid-Enriched Dialysate (Peritoneal Dialysis)

• For malnourished peritoneal dialysis patients with low protein intake (<1.0 g/kg/day), amino acid-based dialysate (1.1% amino acids) can be used for 1-2 exchanges daily 1, 3
• This approach brings total protein plus amino acid intake to 1.1-1.3 g/kg/day 3
• Clinical studies demonstrate improved nitrogen balance, increased net protein anabolism, normalized plasma amino acid patterns, and increased serum total protein and transferrin with this intervention 3
• Critical caveat: Patients must have adequate energy intake (25-30 kcal/kg/day) to prevent amino acids from being used as an energy source rather than for protein synthesis 4
• Monitor for mild metabolic acidemia, which can occur with amino acid dialysate 3

Branched-Chain Amino Acids (BCAAs) in Hemodialysis

• Hemodialysis causes marked depletion of essential amino acids, particularly branched-chain amino acids (valine, leucine, isoleucine) 2
• BCAA-enriched dialysate at physiological concentrations can restore plasma BCAA levels and achieve positive mass balance during dialysis sessions 5
• Standard dialysis decreases plasma valine significantly (from 204.5 to 130.8 μmol/L), while BCAA-enriched dialysate increases it (from 197.2 to 269.2 μmol/L) 5
• This approach may help limit muscle catabolism during hemodialysis, though long-term outcome studies are needed 5

Water-Soluble Vitamin Supplementation

All dialysis patients should receive supplementation of water-soluble B vitamins due to dialytic losses. 6

Specific B Vitamin Recommendations:

• Folic acid: 1 mg/day 1
• Pyridoxine (B6): 10-20 mg/day 1, 6
• Vitamin C: 30-60 mg/day 1
• Vitamin B12: Most patients maintain normal levels without supplementation; monitor periodically 6
• Riboflavin (B2): Supplementation as part of B-complex may help reduce elevated homocysteine 6

The American Journal of Kidney Diseases recommends aiming for 100% of the Dietary Reference Intake (DRI) for most B vitamins 6

L-Carnitine Supplementation

Routine L-carnitine supplementation is NOT recommended for all maintenance dialysis patients. 1

• While L-carnitine may improve subjective symptoms (malaise, muscle weakness, intradialytic cramps, hypotension) in selected patients, evidence is insufficient for routine use 1
• The most promising application is treatment of erythropoietin-resistant anemia 1
• L-carnitine should only be considered after standard therapy has been attempted and failed 1

Energy Requirements

Target energy intake: 35 kcal/kg/day for patients <60 years; 30-35 kcal/kg/day for patients ≥60 years 1

• For peritoneal dialysis patients, include glucose absorbed from dialysate when calculating total energy intake 1
• Energy expenditure in dialysis patients is similar to healthy individuals, supporting these recommendations 1
• Adequate energy intake is essential to maintain neutral nitrogen balance and prevent protein from being catabolized for energy 1

Monitoring and Intervention Algorithm

Step 1: Assess Nutritional Status

• Monitor serum albumin every 1-4 months (target: maintain in normal range) 1
• Calculate normalized protein nitrogen appearance (nPNA): target ≥0.9 g/kg/day 1
• Evaluate body mass index (BMI): concern if <20 kg/m² 1
• Assess for >10% body weight loss over 6 months 1

Step 2: Dietary Counseling

• If protein intake is inadequate, initiate dietary counseling and education first 1
• Ensure at least 50% of protein comes from high biological value sources 1

Step 3: Oral Supplementation

• If dietary counseling fails to achieve targets, prescribe oral nutritional supplements 1
• Oral supplements have been shown to increase serum albumin by 2.3 g/L in undernourished hemodialysis patients 1

Step 4: Advanced Nutritional Support

• If oral supplements are not tolerated or effective and malnutrition persists, consider tube feedings 1
• For peritoneal dialysis patients specifically, amino acid-enriched dialysate is an option 1, 3
• For patients unable to meet needs enterally, consider IDPN or TPN 1

Critical Pitfalls to Avoid

• Do not increase protein intake without ensuring adequate energy intake: Amino acids will be oxidized for energy rather than used for protein synthesis 4
• Do not ignore dialysis adequacy: Low protein intake may reflect inadequate dialysis dose; evaluate and optimize dialysis prescription before aggressive nutritional intervention 1
• Do not overlook treatable causes of malnutrition: Address acidosis, hyperparathyroidism, gastroparesis, and infections before attributing malnutrition solely to inadequate intake 1
• Do not use amino acid dialysate in well-nourished patients: This intervention is specifically for malnourished patients with documented low protein intake 3, 4
• Monitor for metabolic acidosis: Amino acid supplementation (especially via dialysate) can worsen acidemia; ensure adequate buffer in solutions 3, 4