What are the key parameters for a hemodialysis prescription?

Hemodialysis Prescription Parameters

For patients with end-stage kidney disease requiring hemodialysis, prescribe three sessions per week with a minimum duration of 3 hours per session, targeting a single-pool Kt/V of 1.4 (with prescribed Kt/V of 1.3 to ensure minimum delivered dose of 1.2 is achieved), using biocompatible high or low flux membranes. 1, 2

Core Prescription Components

Frequency

• Three sessions per week is the standard frequency for all patients requiring hemodialysis unless significant residual kidney function (≥5 mL/min) is present 1, 2
• Twice-weekly hemodialysis is inadequate except when substantial residual kidney function exists, which must be monitored serially every 3 months to determine appropriate timing for transition to thrice-weekly sessions 1

Session Duration

• Prescribe a bare minimum of 3 hours per session for patients with low residual kidney function (<2 mL/min) 1, 2
• This minimum applies specifically to thrice-weekly conventional hemodialysis 1, 2

Dialysis Adequacy Targets

• Target single-pool Kt/V (spKt/V) of 1.4 per hemodialysis session for thrice-weekly treatments 1, 2
• Prescribe Kt/V of 1.3 to ensure the delivered dose does not fall below the minimum adequate level, as not all patients receive their prescribed dose 1, 2
• Minimum delivered spKt/V must be 1.2 1, 2
• In terms of urea reduction ratio (URR), a Kt/V of 1.3 corresponds to an average URR of 70%, though this varies with ultrafiltration 1

Membrane Selection

• Use biocompatible membranes, either high or low flux, for intermittent hemodialysis 1, 2

Adjustments for Special Circumstances

When to Extend Treatment Time or Frequency

Consider additional sessions or longer treatment times for patients with: 1, 2

• Large interdialytic weight gains
• High ultrafiltration rates
• Poorly controlled blood pressure
• Difficulty achieving dry weight
• Poor metabolic control (hyperphosphatemia, metabolic acidosis, hyperkalemia)

Residual Kidney Function Considerations

• In patients with significant residual kidney function (Kru), dialysis dose may be reduced provided Kru is measured periodically (within 3 months) to avoid inadequate dialysis 1, 2
• For non-thrice-weekly schedules, target a standard Kt/V of 2.3 volumes per week with minimum delivered dose of 2.1, using calculations that include contributions from ultrafiltration and residual kidney function 1, 2

Ultrafiltration and Volume Management

Ultrafiltration Rate Prescription

• Prescribe an ultrafiltration rate that balances achieving euvolemia and adequate blood pressure control while minimizing hemodynamic instability and intradialytic symptoms 1, 2
• Combine dietary sodium restriction with adequate sodium/water removal to manage hypertension, hypervolemia, and left ventricular hypertrophy 1, 2

Common Pitfalls in Achieving Prescribed Dose

Factors That Reduce Delivered Dose Below Prescription

The delivered dose frequently falls below prescribed levels due to: 1

Compromised urea clearance from:

• Access recirculation reducing concentration gradient in the dialyzer 1
• Inadequate blood flow from vascular access 1
• Dialyzer clotting during dialysis reducing effective surface area 1
• Blood pump/dialysate flow calibration errors 1
• Dialyzer leaks 1

Reductions in effective treatment time from:

• Inaccurate time measurement (using wristwatches instead of synchronized dialysis unit clocks) 1
• Treatment interruptions due to clinical complications or equipment alarms 1

Critical Monitoring Beyond Kt/V

Adequate dialysis must address more than just Kt/V targets: 1, 2

• Potassium removal
• Correction of metabolic acidosis
• Adequate protein/caloric intake to prevent malnutrition
• Sufficient fluid removal to achieve euvolemia

Alternative Regimens

Extended Dialysis Options

• Short frequent hemodialysis (5-7 sessions per week, 2-3 hours each) may be offered after discussing potential quality of life benefits and risks 1, 2
• Home long hemodialysis (nocturnal or extended sessions) may be considered for patients preferring this for lifestyle considerations, with counseling about increased vascular access complications, potential caregiver burden, and accelerated decline in residual kidney function 1, 2