What are the guidelines for dialysis adequacy?

Guidelines on Dialysis Adequacy

The minimum delivered dose of hemodialysis for thrice-weekly treatments should be a single-pool Kt/V (spKt/V) of 1.2, with a target prescribed dose of spKt/V 1.4 to ensure adequate delivery, and treatments should last at least 3 hours for patients with minimal residual kidney function. 1, 2

Hemodialysis Frequency and Duration

Standard Thrice-Weekly Hemodialysis

• Minimum delivered dose: spKt/V of 1.2 per session 1
• Target prescribed dose: spKt/V of 1.4 per session (to account for potential variability in delivery) 2
• Minimum treatment time: 3 hours per session for patients with residual kidney function <2 mL/min 1
• Standard frequency: Three times per week is recommended for most patients 1

Alternative Schedules

• Twice-weekly hemodialysis:
  • Only appropriate for patients with substantial residual kidney function (GFR ≥5 mL/min) 1
  • Requires regular monitoring of residual kidney function (at least quarterly) 1
• More frequent schedules (4-6 times/week):
  • Should achieve a minimum standard Kt/V (stdKt/V) of 2.0 per week 1
  • May benefit patients with specific issues such as hyperphosphatemia or chronic fluid overload 1

Patient-Specific Considerations

Adjustments Based on Patient Characteristics

• Women of any body size may require increased dialysis doses 1
• Smaller patients (modeled V ≤25L) may require increased dialysis doses 1
• Malnourished patients (weight ≥20% below peer body weight) or those with unexplained weight loss should receive increased dialysis dose and/or frequency 1

Residual Kidney Function

• Dialysis dose can be reduced for patients with significant residual kidney function (>2 mL/min/1.73m²) 1
• When reducing dose based on residual function:
  • Monitor residual function at least quarterly
  • Reassess immediately after any event that might reduce kidney function 1
  • Reduced target should be no lower than 60% of the minimum target for patients without residual function 1

Dialysis Membrane and Technique Considerations

Membrane Selection

• High-flux membranes (β2-microglobulin clearance ≥20 mL/min) are recommended when good water quality is available 1
• High-flux membranes may provide benefits for patients with longer dialysis vintage, particularly for cardiovascular outcomes 2

Hemofiltration or Hemodiafiltration

• Minimum dose targets for these techniques should be the same as for standard hemodialysis 1

Quality Assurance and Monitoring

Measurement Frequency

• Measure delivered dose at least monthly 2
• Increase measurement frequency when:
  • Patients are non-compliant with treatment schedules
  • Problems with delivery of prescribed doses occur
  • Wide variability in urea kinetic modeling results is observed
  • Hemodialysis prescriptions are modified 2

Common Pitfalls to Avoid

1. Focusing solely on Kt/V while neglecting other aspects of adequacy:

   • Even with adequate Kt/V, patients may have inadequate potassium removal, uncorrected acidosis, or insufficient fluid removal 1, 2
   • Consider the patient's overall clinical status, not just urea clearance metrics

2. Inadequate blood sampling technique:

   • Improper sampling can lead to inaccurate Kt/V calculations
   • Predialysis and postdialysis BUN samples must be drawn at the same session 2

3. Factors that can compromise delivered dose:

   • Access recirculation
   • Inadequate blood flow
   • Dialyzer clotting
   • Blood pump calibration errors
   • Reductions in treatment time 1

4. Neglecting the importance of treatment time:

   • Short dialysis sessions may achieve target Kt/V but fail to provide adequate fluid removal 1, 3
   • Rapid ultrafiltration can lead to intradialytic symptoms and poor volume control 3

Beyond Urea Clearance

Remember that dialysis adequacy encompasses more than just urea clearance. Additional considerations include:

• Volume status and blood pressure control
• Electrolyte balance (particularly potassium)
• Acid-base balance
• Phosphate removal
• Middle molecule clearance
• Quality of life and symptom management 1, 2

For pediatric patients, additional attention should be given to school/vocational performance, growth, and emotional development 1.

The dialysis prescription should ultimately balance achieving adequate solute clearance with minimizing symptoms and optimizing patient outcomes in terms of morbidity, mortality, and quality of life.