High-Flux vs. Low-Flux Dialyzer Selection and Prescription Parameters
Yes, a patient can use a high-flux dialyzer instead of a low-flux dialyzer, and KDOQI guidelines recommend either option as acceptable, though high-flux dialyzers offer cardiovascular mortality benefits in specific patient populations. 1
Dialyzer Selection Algorithm
General Population
- Both high-flux and low-flux dialyzers are acceptable for routine hemodialysis, as large randomized trials showed no overall survival difference between the two 1
- The choice should balance potential cardiovascular mortality benefit (18% reduction with high-flux, HR 0.82) against local cost and availability 1
Priority Populations for High-Flux Dialyzers
Strongly consider high-flux dialyzers for patients with:
- Diabetes mellitus - demonstrated improved survival in post-hoc analyses of multiple trials 1
- Serum albumin ≤4 g/dL - showed 51% mortality reduction (RR 0.49) in the MPO trial 1
- Dialysis vintage >3.7 years - HEMO Study demonstrated significant mortality benefit in this subgroup 1
- AV fistula access - EGE Study post-hoc analysis showed improved cardiovascular event-free survival 1
Safety Profile
- No increased harm with high-flux dialyzers - no differences in infection rates, hospitalization rates, or vascular access complications between high-flux and low-flux groups 1
- Quality of life parameters were equivalent between groups (except minor improvements in sleep quality and patient satisfaction with high-flux) 1
Blood Flow Rate (BFR) Settings
Standard Blood Flow Rates
- Target BFR: 300-450 mL/min for both high-flux and low-flux dialyzers in stable patients
- Minimum effective BFR: 200-250 mL/min for adequate small solute clearance
Critical Caveat for High-Flux Dialyzers
- High-flux dialyzers achieve substantially higher urea clearance at any given blood flow rate compared to low-flux dialyzers 2
- A high-flux dialyzer (F180NR) at 150 mL/min BFR achieves higher urea clearance (144 mL/min) than a low-flux dialyzer (F5) at 300 mL/min BFR (130 mL/min) 2
- In hemodynamically unstable or acute dialysis patients at risk for disequilibrium syndrome, high-flux dialyzers may NOT be safer even with reduced blood flow - consider low-flux dialyzers in these high-risk situations 2
Blood Flow Adjustments
- Reduce BFR to 150-200 mL/min in patients with:
- Hemodynamic instability
- Risk of dialysis disequilibrium syndrome
- New to dialysis (first few sessions)
- Poor vascular access function
- Increase BFR to 400-450 mL/min in patients with:
- Good vascular access (mature AV fistula)
- Need for enhanced clearance
- Larger body size
Dialysate Flow Rate (DFR) Settings
Standard DFR
- Target DFR: 500-800 mL/min for both high-flux and low-flux dialyzers
- Most common prescription: 500 mL/min for routine thrice-weekly hemodialysis
- Maximum DFR: 800 mL/min when enhanced clearance is needed
DFR Optimization
- Maintain DFR:BFR ratio of approximately 1.5:1 to 2:1 for optimal small solute clearance
- Example: BFR 300 mL/min → DFR 500-600 mL/min
- Higher DFR (600-800 mL/min) provides marginal benefit once adequate BFR is achieved, but may be used to maximize Kt/V
Special Consideration for High-Flux Dialyzers
- Ultrapure dialysate is strongly recommended for high-flux dialyzers due to risk of backfiltration and backdiffusion of dialysate contaminants 3
- Bacterial counts <0.1 CFU/mL and endotoxin <0.03 IU/mL should be maintained 3
- Standard dialysate quality may expose high-flux patients to inflammatory complications from backtransport of endotoxin fragments 3
Practical Prescription Example
For Standard Patient (No High-Risk Features)
- Dialyzer: High-flux or low-flux (either acceptable)
- BFR: 300-400 mL/min
- DFR: 500-600 mL/min
- Treatment time: 3.5-4 hours, thrice weekly
For Priority High-Flux Patient (Diabetes, Low Albumin, Long Vintage, or AV Fistula)
- Dialyzer: High-flux (preferred for mortality benefit) 1
- BFR: 350-450 mL/min
- DFR: 600-800 mL/min
- Treatment time: 4 hours, thrice weekly
- Dialysate quality: Ultrapure 3
For Hemodynamically Unstable or Acute Patient
- Dialyzer: Low-flux (safer for gradual solute removal) 2
- BFR: 150-200 mL/min
- DFR: 300-400 mL/min
- Treatment time: Extended as tolerated
Monitoring Requirements
Dialyzer Performance Tracking
- Monitor Kt/V and URR monthly to ensure adequate clearance regardless of dialyzer type 4
- For reused dialyzers: Ensure blood compartment volume ≥80% of original or urea clearance ≥90% of original 4
- High-flux dialyzers show minimal decline in small solute clearance with reuse (1-2% per 10 reuses), but large molecule clearance (β2-microglobulin) decreases substantially with reuse 4, 5
Key Pitfall to Avoid
Do not assume maintained small solute clearance (urea, creatinine) guarantees maintained large solute clearance in reused high-flux dialyzers - β2-microglobulin clearance and protein loss decrease significantly with reuse even when urea clearance remains stable 5