Kt/V Target for Twice-Weekly Hemodialysis
Twice-weekly hemodialysis is generally not recommended for patients without substantial residual kidney function (residual kidney clearance < 2 mL/min/1.73 m²), as it is impossible to achieve adequate dialysis dosing on this schedule alone. 1
Critical Prerequisite: Residual Kidney Function Assessment
- Twice-weekly HD should only be considered if the patient has residual kidney clearance (Kr) ≥ 2 mL/min/1.73 m² 1
- If Kr is < 2 mL/min/1.73 m², twice-weekly dialysis is explicitly contraindicated and the patient must transition to at least three times weekly 1
- Some guidelines suggest Kr should ideally be > 3 mL/min/1.73 m² for twice-weekly schedules 1
Kt/V Targets for Twice-Weekly Dialysis
For Patients WITH Adequate Residual Function (Kr ≥ 2 mL/min/1.73 m²):
- Target single-pool Kt/V (spKt/V) per session: 2.0 1
- This target assumes the patient has preserved residual kidney function contributing to overall solute clearance 1
- The goal is to achieve a minimum standard Kt/V (stdKt/V) of 2.0 per week when combining dialysis clearance with residual kidney function 1
Important Caveats:
- Without residual kidney function, it is mathematically impossible to reach an adequate stdKt/V of 2.0 per week using only twice-weekly dialysis 1
- The spKt/V of 2.0 per session represents a minimum value, not an optimal target—consider prescribing 15% higher (approximately 2.3 per session) to account for measurement variability 1
Mandatory Monitoring Requirements
- Residual kidney function must be measured at least quarterly to ensure it remains adequate to support the twice-weekly schedule 1
- Measure Kr immediately after any clinical event that might acutely reduce residual function (hypotension, nephrotoxic medication exposure, contrast administration, etc.) 1
- If Kr declines below 2 mL/min/1.73 m², immediately transition to thrice-weekly dialysis 1
Clinical Reasoning
The 2006 KDOQI guidelines used kinetic modeling to determine that achieving adequate weekly solute clearance (stdKt/V of 2.0) on a twice-weekly schedule requires both high per-session Kt/V and substantial residual kidney function 1. The more recent 2015 KDOQI update reinforces that for non-thrice-weekly schedules, the target should be a standard Kt/V of 2.3 volumes per week with minimum delivered dose of 2.1, incorporating contributions from ultrafiltration and residual kidney function 1, 2.
Common Pitfalls to Avoid
- Do not assume twice-weekly dialysis is adequate based solely on patient preference or logistical convenience—this schedule requires objective documentation of preserved residual kidney function 1
- Do not neglect serial monitoring of residual function—patients can lose residual kidney function gradually or acutely, making the twice-weekly schedule inadequate 1
- Remember that Kt/V alone does not capture all aspects of dialysis adequacy—also monitor potassium removal, acid-base status, nutritional parameters, and volume status 2