What are the guidelines for ensuring dialysis adequacy in patients undergoing dialysis?

Dialysis Adequacy Guidelines

For standard thrice-weekly hemodialysis, target a delivered single-pool Kt/V (spKt/V) of at least 1.4, with a minimum acceptable delivered dose of 1.2, and ensure treatment duration is at least 3 hours per session for patients with residual kidney function (Kr) less than 2 mL/min/1.73 m². 1

Core Adequacy Targets

Standard Thrice-Weekly Hemodialysis

• Prescribe a target spKt/V of at least 1.4 to account for measurement variability and ensure the delivered dose does not fall below the minimum of 1.2 1
• The target should be 15% higher than the minimum dose because of inherent variability in Kt/V measurement 1
• Minimum treatment time must be at least 3 hours per session for patients with Kr <2 mL/min/1.73 m² 1
• This minimum spKt/V of 1.2 was validated by the HEMO Study for mortality and morbidity outcomes 1

Alternative Frequency Schedules

• For varying dialysis frequencies (2,4, or 6 times weekly), target a minimum standardized Kt/V (stdKt/V) of 2.0 per week rather than using the per-session target 1
• Twice-weekly hemodialysis is contraindicated in patients with Kr <2 mL/min/1.73 m² due to inadequate clearance 1
• Patients with Kr >2 mL/min/1.73 m² may be candidates for twice-weekly dialysis if they have stable residual function and avoid excessive fluid gains 1

Membrane Selection

Use high-flux membranes when adequate dialysate water quality is available, defined as providing β2-microglobulin clearance of at least 20 mL/min under actual use conditions 1

• High-flux dialysis showed approximately 10% mortality benefit in the HEMO Study, particularly in patients dialyzed longer than 3.7 years 1
• High-flux membranes reduce dialysis-related amyloidosis risk in long-term dialysis patients (>5 years) 1

Special Population Adjustments

Patients with Residual Kidney Function

• Reduce the minimum spKt/V target to no lower than 60% of the standard minimum for patients with substantial RKF (Kr >2 mL/min/1.73 m²) 1
• Monitor Kr at least quarterly and immediately after any event that might acutely reduce residual function 1
• Preservation of residual kidney function is critical as it significantly impacts quality of life 1, 2

Women and Smaller Patients

Consider increasing the minimally adequate dose for:

• All women regardless of body size 1
• Smaller patients with anthropometric or modeled volume (V) ≤25 L 1

The rationale is that Kt/V may underestimate the required dose in these populations, as V/BSA and V/W^0.67^ conversion factors differ significantly by sex and body size 3

Malnourished or Weight-Losing Patients

Increase the dialysis dose and/or switch to more frequent dialysis for:

• Patients with weights ≤20% below peer body weights 1
• Patients with recent unexplained, unplanned weight loss 1

A critical pitfall: weight loss from malnutrition decreases V, artificially increasing Kt/V values, which may mask inadequate dialysis and lead to harm if the dose is reduced 1

Patients Requiring More Frequent Dialysis

Consider switching to more frequent schedules for:

• Patients with chronic fluid overload with or without refractory hypertension 1
• Patients with hyperphosphatemia refractory to standard management 1

More frequent dialysis (daily or nocturnal) improves blood pressure control, left ventricular hypertrophy regression, quality of life, and sleep quality 1, 4

Dose Monitoring and Quality Assurance

Measurement Requirements

• Calculate delivered Kt/V using pre- and post-treatment BUN levels for all patients 1
• Compare modeled volume (V) with anthropometric formulas (e.g., Watson) to detect delivery problems 1
• When modeled V is significantly greater than expected, investigate for access recirculation, timing errors, blood pump calibration issues, dialysate pump malfunction, blood sampling errors, or dialyzer clotting 1

Initiation Criteria

Initiate dialysis when weekly renal Kt/V (Krt/V) falls below 2.0, unless the patient maintains:

• Stable or increased edema-free body weight 1
• Adequate nutritional parameters (serum albumin above lower limit of normal and stable/rising) 1
• Lean body mass ≥63% 1

Starting dialysis earlier may prevent or reverse nutritional deterioration that commonly occurs as GFR declines below 25-50 mL/min 1

Common Pitfalls to Avoid

• Do not rely solely on Kt/V as the only measure of adequacy; assess potassium removal, acid-base correction, fluid removal, and nutritional status 1
• Do not reduce dialysis dose in malnourished patients even if Kt/V appears adequate, as the elevated Kt/V may reflect reduced V from malnutrition rather than adequate clearance 1
• Do not prescribe exactly 1.2 spKt/V; the target must be higher (≥1.4) to ensure the delivered dose consistently exceeds the minimum threshold 1
• Monitor for cardiovascular complications during and for 4-5 hours after dialysis, as arrhythmias occur in 76% of maintenance hemodialysis patients 2