Basics

High Efficiency vs High Flux

High Efficiency

High Flux

 Membrane Characteristics
  •  Numerous pores, thin membrane, and high surface area allowing high small molecule (urea) clearance
  • Larger pores allowing better middle molecule (β2 microglobulin) clearance

 General Characteristics
(high diffusive clearance)

  • Dialyzer urea clearance rate (K) is usually >210 mL/min
  • High KoA (determines ‘efficiency’) – KoA urea of the dialyzer is usually > 800-1000 mL/min. Remember that the in vitro KoA provided by the manufacturer is often 20% higher than in vivo values.
  • Kuf is variable
  • Clearance of middle molecular weight molecules (β2 microglobulin) is variable
 (high convective clearance)

  • Kuf (determines ‘flux’) of dialyzer is high (>15-20ml/h/mm Hg)
  • Clearance of middle molecules (β2 microglobulin ) is high (>20ml/min)

Technical Requirements
  • Dialyzer with a high KoA (>800-1000ml/min)
  • High blood flow (≥350 mL/min)
  • High dialysate flow (≥500 mL/min)
  • Bicarbonate dialysate (it is important to use  Bicarbonate-containing dialysate to avoid symptoms associated with acetate intolerance (i.e., nausea, vomiting, headache, hypotension, worsening of metabolic acidosis, and cardiac arrhythmia)
  • Dialyzer with a high Kuf
  • Ultrapure water for dialysis
  • Automated ultrafiltration control is necessary to avoid errors in TMP calculation that can result in massive flux of water across a high flux membrane and hemodynamic instability

More on High Flux Dialysis

  • HEMO study1 did not show a mortality benefit between high flux and low flux dialysis.
  • However, the HEMO study, MPO2 trial, and EGE3 trial showed a survival benefit (especially cardiovascular) in subset of patients with albumin≤4mg/dl, dialysis vintage ≥3.7 years, diabetes or those with an AV fistula.
  • KDOQI Adequacy Work group recommends use of high flux dialyzers routinely as long as appropriate water treatment is available.

Sources:

  1. Eknoyan G, Beck, GJ Cheung AK, et al. Effect of dialysis dose and membrane flux in maintenance hemodialysis. N Engl J Med 2002; 347:2010. Hemodialysis study(HEMO)
  2. Locatelli, martin-Malo, Hannedouche et al. Membrane permeability Outcome (MPO) study group. Effect of membrane permeability on survival of hemodialysis patients. JASN 2009;20(3):645
  3. Asci, Tz, Ozkahya et al. EGE study group. The impact of Membrane permeability and dialysate purity on cardiovascular outcomes.JASN 2013 May;24(6):1014-23