How to manage and improve appetite in patients with impaired renal function?

Managing and Improving Appetite in Patients with Impaired Renal Function

Optimize dialysis adequacy first by ensuring weekly Kt/Vurea ≥2.0 for hemodialysis patients and appropriate creatinine clearance targets for peritoneal dialysis patients, as inadequate dialysis directly causes uremic anorexia through toxin accumulation. 1, 2

Address Underlying Reversible Causes

Before implementing nutritional interventions, systematically eliminate factors suppressing appetite:

Optimize Dialysis Adequacy

• Ensure weekly Kt/Vurea ≥2.0 for hemodialysis patients, as inadequate dialysis (Kt/Vurea <2.0) directly causes uremic symptoms including nausea, vomiting, and anorexia 1, 2
• For peritoneal dialysis patients, target creatinine clearance ≥60 L/week/1.73 m² for high/high-average transporters or ≥50 L/week/1.73 m² for low/low-average transporters 1
• Increasing dialysis dose may improve appetite by reducing uremic toxins, though evidence for improved nutritional markers from dose increases alone remains limited 1

Treat Metabolic Derangements

• Correct metabolic acidosis, which contributes to appetite suppression and protein catabolism 3, 2
• Address hormonal deficiencies that may impair appetite 3
• Evaluate and treat insulin resistance, which disrupts normal metabolic signaling 2

Manage Inflammation

• Recognize that chronic inflammation produces proinflammatory cytokines (TNF-α, IL-6) directly associated with diminished appetite 1, 2, 4, 5
• Anti-inflammatory interventions represent emerging therapies, though specific protocols require further validation 3, 6
• Poor appetite is associated with elevated C-reactive protein >10 mg/L (odds ratio 2.39) 4

Review Medications and Comorbidities

• Eliminate or modify medications interfering with appetite 3
• Treat superimposed acute or chronic diseases, psychiatric illnesses, and gastroparesis 3, 2
• Address mechanical impairments (lack of dentures) and cultural food preferences 3

Nutritional Support Strategies

First-Line: Dietary Counseling and Oral Nutritional Supplements (ONS)

• Provide intensive nutritional counseling by an experienced renal dietitian as the initial intervention 3, 7
• Offer ONS when oral intake fails to meet ≥70% of daily macronutrient requirements 3, 1, 7
• ONS can add 10-12 kcal/kg and 0.3-0.5 g protein/kg daily when provided twice daily 3
• Administer ONS 2-3 hours after usual meals to avoid suppressing regular food intake 7
• Late evening ONS reduces overnight catabolism without affecting daytime food consumption 7
• Intradialytic delivery of ONS during hemodialysis sessions improves compliance 7
• ONS combined with dietary counseling should be attempted before considering intradialytic parenteral nutrition 1

Second-Line: Enteral Nutrition

• If oral intake including ONS remains inadequate after counseling, consider tube feeding if medically appropriate 3, 7
• Enteral nutrition is indicated when oral intake cannot meet at least 70% of daily requirements 3
• Tube feeding has been used successfully in infants and children receiving maintenance dialysis 3

Third-Line: Intradialytic Parenteral Nutrition (IDPN)

• Reserve IDPN for malnourished hemodialysis patients who fail to respond to or cannot tolerate ONS or enteral nutrition 3, 1, 7
• IDPN provides nutrients during the 3-4 hour hemodialysis session three times weekly 3, 1
• Multiple RCTs showed nutritional improvements with IDPN in patients with overt protein-energy wasting 3
• IDPN is non-superior to ONS but represents a reasonable option when first-line treatments fail 3

Fourth-Line: Total Parenteral Nutrition

• Consider daily total or partial parenteral nutrition if the combination of oral intake and IDPN does not meet protein and energy requirements 3

Nutritional Targets

Protein Requirements

• Target protein intake of 1.2 g/kg/day for stable hemodialysis patients 7
• Do not restrict protein intake to <0.8 g/kg/day in dialysis patients, as malnutrition risk exceeds theoretical benefits of protein restriction 1
• At least 50% of protein should come from high biological value sources (animal proteins, whey, egg albumin) 7
• In acute sepsis or critical illness, increase protein to 1.2-1.5 g/kg/day 7

Energy Requirements

• Target 30-35 kcal/kg/day for patients ≥60 years old 7
• Adequate energy intake prevents protein catabolism for energy 7

Monitoring Parameters

Nutritional Markers

• Monitor normalized protein nitrogen appearance (nPNA) targeting ≥0.9-1.1 g/kg/day, as values below this suggest inadequate protein intake 1, 7
• Assess serum albumin every 1-4 months, maintaining above the lower limit of laboratory normal range 1, 7
• Monitor for >10% body weight loss over 6 months and maintain BMI >20 kg/m² 7
• Use subjective global assessment (SGA) and edema-free body weight trends 1

Metabolic Monitoring

• Monitor plasma electrolytes and phosphorus closely when initiating nutritional support to prevent refeeding syndrome 7
• The dialysis regimen should be regularly monitored and modified to treat any intensification of uremia caused by increased protein intake 3, 7
• Monitor phosphorus and potassium content carefully when increasing protein intake, as protein-rich foods are major sources of these minerals 7

Emerging Pharmacologic Appetite Stimulants

Considerations for Appetite Stimulants

• Appetite stimulants represent emerging therapies for protein-energy wasting 3
• Megestrol acetate carries significant risks including new-onset diabetes, Cushing's syndrome, and adrenal insufficiency with chronic use 8
• Laboratory evaluation for adrenal insufficiency and consideration of stress-dose glucocorticoids are strongly recommended in patients receiving chronic megestrol acetate 8
• Mirtazapine causes appetite increase in 17% of patients and weight gain ≥7% in 7.5% of patients, but also causes somnolence in 54% of patients 9
• Mirtazapine carries risks of QTc prolongation, serotonin syndrome, and DRESS syndrome 9

Anabolic Strategies

• Anabolic steroids, growth hormone, and exercise in combination with nutritional supplementation have shown improvements in protein stores 3
• These represent potential additional approaches for treating protein-energy wasting 3

Critical Pitfalls to Avoid

• Do not delay nutritional intervention: inadequate intake for even days to 2 weeks can worsen outcomes depending on baseline nutritional status 7
• Avoid overfeeding, particularly glucose administration exceeding 7 mg/kg/min, which increases hepatic complication risk 7
• Do not use IDPN as first-line therapy: ONS combined with dietary counseling should be attempted first 3, 1
• Recognize that hospitalized dialysis patients often ingest only 66% of protein and 50% of energy requirements even when needs increase during acute illness 3, 2
• Poor appetite is associated with 4-fold increased mortality risk (hazard ratio 4.74), making aggressive intervention essential 5