Hemodiafiltration and
Hemofiltration
By Dr Tamaddondar
Hormozgan university of medical
science
Diffusion
V of solution
used is 5fold
higher than
replacement in
hemofiltration
Convection
+/-Diffusion
HDF 8 – 15 L
HF 20-40L
replacement
solution
• A. Review of diffusion versus convectionbased clearances
• B. Hemodiafiltration versus hemofiltration
• C. Clearance due to diffusion (dialysis) versus
filtration in HDF
• D. Predilution versus postdilution mode
• E. Technical issues
• F.Risk and benefits
PORE SIZE
PORE SIZE
HIGH-PERFORMANCE
EXTRACORPOREAL THERAPIES FOR
END-STAGE RENAL DISEASE
1-High-efficiency hemodialysis
2-High-flux hemodialysis
3-Hemofiltration(intermittent)
4-Hemodiafiltration( intermittent)
Online Hemodiafiltration
• Hemodiafiltration permits β2-microglobulin
removal and high Kt/V, and is probably the
best way to treat chronic renal failure (CRF).
Clearance due to diffusion (dialysis)
versus filtration in HDF
• Ktotal = KDiffusive + F/2 (if UF<100ml/min)
Predilution versus postdilution mode
• The administration may take place either
before (predilution) or after (postdilution) the
hemofilter.
• Infusing replacement solution in predilution
mode in HDF reduces significantly the effect
on clearance due to a dilution of the blood
entering the dialyzer.
Technical issues
• Water
• Fluid paths(HF/HDF)
• Online preparation of replacement solution
and dialysis solution
• Vascular access
• Membrane
Water
ultrapure water
(virtually sterile and nonpyrogenic water)
• Current AAMI recommendations <200(CFU)/mL of bacteria
<2.0 endotoxin units (EU)/mL of endotoxin
• ultrapure dialysis solution<0.1 CFU/mL and <0.03 EU/mL
endotoxin
• The ultrafilters are replaced periodically to
prevent supersaturation and release of
endotoxins.
Fluid paths(HF/HDF)
post-dilution hemofiltration
post-dilution hemodiafiltration
Online preparation of replacement
solution and dialysis solution
• Bicarbonate-based dialysate solution is
universally used as the starting point. The
production of sterile and nonpyrogenic
dialysis fluid (ultrapure dialysate) is achieved
by “cold sterilization” of the freshly prepared
dialysate using an ultrafilter.
balancing chamber
flow-metric equalizer
Infusion
module
0-250
mL/min
U8000S polyamide S
Gambro 3-filter
hemodialysis system
Diasafe® plus, Polysulfone®
FME 2-filter hemodialysis system
Vascular access
• Patients treated with HF/HDF require an
access capable of delivering an extracorporeal
blood flow of at least 350 mL per minute, and
preferably higher.
Membrane
Flux
• Measure of ultrafiltration capacity
• Low and high flux are based on the ultrafiltration coefficient (Kuf)
• Low flux: Kuf <10 mL/h/mm Hg
• High flux: Kuf >20 mL/h/mm Hg
Permeability
• Measure of the clearance of the middle molecular weight molecule (eg,
β2-microglobulin)
• General correlation between flux and permeability
• Low permeability: β 2-microglobulin clearance <10 mL/min
• High permeability: β 2-microglobulin clearance >20 mL/min
Efficiency
• Measure of urea clearance
• Low and high efficiency are based on the urea KoA value
• Low efficiency: KoA <500 mL/min
• High efficiency: KoA >600 mL/min
Membrane
• The membrane should have a high hydraulic
permeability (KUF ≥50 mL / hour / mm Hg),
high solute permeability (K0A urea >600) and
beta2-microglobulin clearance >60 mL/ min),
and large surface of exchange (1.50-2.10 m2).
Typical prescriptions and substitution
fluid infusion rates
• The conventional HDF/HF treatment schedule
is based on three dialysis sessions per week of
4 hours (12 hours per week).
the substitution volume
HF
• postdilution= Kt/v*55% body weight
• predilution= 2*Kt/v*55% body weight
Kt/v=1
BW=60KG
Pre=60cc/min
Post=30cc/min
the substitution volume
HDF
• QB=500ml/min
• QD=500-1000ml/min
• Typical replacement fluid infusion flow rates= 100
mL/min (24 L for a 4-hour session) in postdilution
HDF and 200 mL/min(48 L for a 40-hour session)
in predilution HDF mode
• simple rule of thumb
Pre=1/3*QB
Post=1/2*QB
Anticoagulation
1-increased sheer forces( activate blood
platelets)
2-significant loss or clearance of heparin
• The large loss of the initial bolus (>50% for unfractionated heparin
(12,000-15,000 daltons) and >80% for low molecular weight heparin
(3,000-6,000 daltons
• Sample protocol using LMWH
• Lovenox 0.5 mg/kg body weight or 50 IU/kg
body weight ,Allow to systemically circulate 34 minutes before starting treatment
• No additional LMWH required unless
treatment exceeds 4 hours If >4 hours inject
400 IU at mid point of treatment via venous
injection port
unfractionated heparin
• Initial bolus 80-100 IU/kg body weight
Inject bolus systemically via venous needle
allowing 3-5 minutes for circulation of heparin
systemically
• Continuous infusion of heparin via pump at
25-35 IU/kg per hr
Potential risks and hazards
• 1-Related to dialysate/water contaminants
Acute reactions- fever, hypotension, tachycardia,
breathlessness, cyanosis, and general malaise
Leukopenia
Chronic reactions- asymptomatic,chronic
microinflammation
• 2- Protein loss(albumin,β2-microglobulin)
• 3- Deficiency syndromes/Soluble vitamins, trace
elements, small peptides, and proteins (vit c
500mg/weekly)
Potential clinical benefits
1-Overall survival/hospitalization benefit
2- Other potential benefits
Overall survival/hospitalization benefit
• Canaud B, et al. Mortality risk for patients receiving
hemodiafiltration versus hemodialysis: European
results from the DOPPS. Kidney Int 2006a;69:20872093.
• ( 35% lower mortality than those treated with lowflux hemodialysis)
• Locatelli F, et al. Comparison of mortality in ESRD
patients on convective and diffusive extracorporeal
treatments. The Registro Lombardo Dialisi E Trapianto.
Kidney Int 1999;55(1):286-293
• (10% reductions in mortality compared to low-flux
dialysis)
Potential clinical benefits
•
•
•
•
•
•
•
•
Intradialytic symptoms.
Residual renal function.
Lower levels of serum inflammatory markers.
Anemia correction?
Malnutrition?
Dyslipidemia and oxidative stress
β2 microglobulin amyloidosis
small protein-bound compounds
Diffusion(dialysis)
convection (hemofiltration)
• depends on solute size
(limited capacity to clear
middle- and large-size
uremic toxins)
• all solutes below the
membrane pore size are
removed at approximately
the same rate(increased
capacity to clear middleand large-size uremic toxins)
• Water driven (solvent drag)
• random molecular motion
• the volume of solution used
is fivefold higher than the
amount of replacement
solution used with
hemofiltration
•
low volume of replacement
solution
• Convective Clearances as a Function of Ultrafiltration in L/Week ,as a Function of
Sieving Coefficient
HDF
• Hemodiafiltration
combines the
characteristics of
conventional HD with
hemofiltration, which
permits increased
clearance for middle and
small molecules.
• only 8 – 15 L of
replacement solution is
used, which is infused
into the venous return of
the extracorporeal circuit.
HF
• the ultrafiltrate flow
through highly permeable
membranes is augmented
by increasingTMP and
hydraulic permeability
with absence of dialysate
flow
• The total volume of
exchange for classic
hemofiltration ranges
from 20 – 40 L per
treatment
Intermittent HDF versus slow
continuous HDF (C-HDF)
• Those who have read through Chapter 13 will notice that this
Gupta-Jaffrin clearance equation is different from what was
described for C-HDF (continuous hemodiafiltration), where the
additive effect of replacement solution to clearance is almost 1:1 in
postdilution mode. The difference is this: In C-HDF, unless quite
high dialysate flow rates are used, the solute concentration of blood
in the dialyzer is reduced only slightly (since the ratio of QB:QD is
quite high). Because of this, increasing ultrafiltration across the
membrane markedly increases solute removal. In intermittent HDF,
the relatively high-efficiency dialysis taking place (with a much
higher ratio of dialysate to blood flow) lowers the solute
concentration of the blood in the dialyzer substantially. Adding a
filtration component is less efficient because the ultrafiltrate now
contains a lower concentration of solute