What constitutes effective hemodialysis?

What Constitutes Effective Hemodialysis

Effective hemodialysis requires achieving a minimum delivered single-pool Kt/V of 1.2 (corresponding to approximately 65% urea reduction ratio) through three sessions per week lasting at least 3 hours each, while simultaneously addressing fluid removal, blood pressure control, electrolyte balance, acid-base correction, and nutritional adequacy. 1

Core Adequacy Parameters

Dialysis Dose Requirements

• Prescribe a target Kt/V of 1.4 per session to ensure the delivered dose does not fall below the minimum adequate level of 1.2 1, 2
• The prescribed dose must exceed the minimum because approximately 50% of patients fail to receive their prescribed hemodialysis dose due to various technical and operational factors 2
• For standard thrice-weekly schedules, target a standard Kt/V of 2.3 volumes per week with minimum delivered dose of 2.1 when including contributions from ultrafiltration and residual kidney function 1

Treatment Frequency and Duration

• Three sessions per week is the standard frequency for all patients unless significant residual kidney function is present 1
• Each session must last a minimum of 3 hours for patients with low residual kidney function 1, 2
• Twice-weekly hemodialysis is inadequate unless substantial residual kidney function exists, which must be monitored serially to guide appropriate timing for transition to thrice-weekly sessions 1

Critical Components Beyond Kt/V

Fluid and Volume Management

• Effective hemodialysis must achieve euvolemia through adequate ultrafiltration while minimizing hemodynamic instability 1, 2
• Prescribe ultrafiltration rates that balance achieving dry weight and adequate blood pressure control against intradialytic symptoms 1
• Combine dietary sodium restriction (≤5g sodium chloride or 2.0g/85 mmol sodium daily) with adequate sodium/water removal to manage hypertension, hypervolemia, and left ventricular hypertrophy 1, 2

Blood Pressure Control

• Elevated blood pressures should be controlled through aggressive extracellular fluid volume management rather than relying solely on antihypertensive medications 2
• The Tassin experience demonstrated that 89% of hypertensive patients required no antihypertensive medications after 3 months of adequate sodium restriction and prolonged dialysis sessions 2

Metabolic and Nutritional Adequacy

• Adequate dialysis must address potassium removal, correction of acidosis, and adequate protein/caloric intake to prevent malnutrition 1
• Monitor normalized protein nitrogen appearance (nPNA) and serum albumin levels as markers of nutritional adequacy 3
• Phosphate control must be achieved, though phosphate binders are typically still required even with adequate dialysis 3

Technical Factors That Compromise Effectiveness

Urea Clearance Compromises

Effective urea clearance depends on dialyzer membrane permeability, surface area, and blood/dialysate flow rates, which can be compromised by: 2

• Access recirculation reducing the concentration gradient in the dialyzer
• Inadequate blood flow from vascular access
• Dialyzer clotting during treatment reducing effective surface area
• Blood pump/dialysate flow calibration errors
• Dialyzer leaks or inadequate reprocessing with reuse
• Inappropriately low dialysate flow rates

Treatment Time Reductions

Effective treatment time must accurately reflect the exact duration during which diffusion occurred at prescribed flow rates: 2

• Common pitfall: Interruptions during treatment due to clinical complications, equipment alarms, fistula needle manipulation, or pump failure reduce actual dialysis time
• Premature discontinuation for staff convenience or patient request
• Delays in starting sessions due to patient tardiness
• Clerical deficiencies in documenting actual treatment start and stop times

Laboratory Sampling Errors

Pre- and post-dialysis BUN measurements may not reflect true systemic urea concentrations due to: 2

• Dilution of predialysis BUN sample with saline
• Drawing predialysis sample after dialysis has started
• Improper timing of postdialysis samples

Membrane Selection and Technology

• Use biocompatible membranes, either high or low flux, for intermittent hemodialysis 1
• Biocompatible membranes may help preserve residual kidney function 4

When to Intensify Treatment

Consider extending session duration beyond 3 hours or increasing frequency beyond thrice-weekly for patients with: 1

• Large interdialytic weight gains
• High ultrafiltration rates
• Poorly controlled blood pressure despite adequate medication
• Difficulty achieving dry weight
• Poor metabolic control

Alternative Intensive Regimens

• Short daily hemodialysis (2-3 hours, 6-7 times weekly) reduces intradialytic hypotension by 20% and improves recovery time from 8 hours to 1 hour 5, 3
• Long nocturnal hemodialysis (8 hours, 3-7 nights weekly) reduces intradialytic hypotension by 68% and provides recovery time of only minutes 5, 2
• These intensive regimens improve treatment tolerability, blood pressure control, and quality of life 5, 3

Residual Kidney Function Considerations

• In patients with significant residual kidney function, dialysis dose may be reduced provided residual function is measured periodically 1
• Preservation of residual kidney function should be prioritized through appropriate medication management and avoiding nephrotoxins 6

Quality Metrics and Monitoring

Effective hemodialysis extends beyond achieving target Kt/V and requires: 7

• Reliable and flexible treatment strategies guided by patient well-being
• Careful evaluation of plasma urea concentrations
• Monitoring for treatment-related side effects including cramps, hypotension, and vascular access problems
• Recognition that hemodialysis extends life but does not treat underlying disease, permitting expression of progressive multisystem disease