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Haemodiafiltration – The New Gold Standard?
Figure 1: Classic Haemodiafiltration and Variants
A F
R – 9L
R – 9L
A V
A V
UFC
UF
UFC
UF
Do Di
Do Di
B
R – 3L
G
A V A
V
UFC
UF
UFC
UF
Do Di
Do Di
C H
R – >15L
R
A V
UFC
UF
UFC
Do Di
Do Di
D I
A
I
A V
A V
Filtr.2
UF UF Do Di
Do Di
Filtr.1
E J
P
1
P
2
A V AV
UFC
UFC
UF
Do+Uf Di
Do Di
A: Classic HDF; B: ‘Soft’ HDF; C: ‘Hard’ HDF; D: Online HDF; E: Internal filtration HDF; F: Paired filtration dialysis; G: Online HDF with endogenous reinfusion; H: Mid-dilution HDF;
I: Double high-flux HDF; J: Push/pull HDF.
(iHDF) enhances proximal water flux by applying a constriction to the haemodialyser. Modifications of PFD are online HDF with endogenous
middle of the fibre bundle (see Figure 1E). By placing an obstruction to re-infusion (HFR) and PFD with online exogenous re-infusion techniques
dialysate flow in the dialysate compartment or by reducing the inner (PHF). In HFR (see Figure 1G) the ultrafiltrate produced is purified by
diameter of the fibres, internal filtration can reach values of absorption through a resin/charcoal unit and subsequently utilised as a
40–50ml/minute in a 1.8m
2
dialyser. The ultrafiltration control system replacement fluid. In PHF with exogenous re-infusion, the first unit is used
of the machine operates a fluid balance, increasing the relative amount to backfilter some fresh dialysate that then acts as ultra-pure online
of backfiltration.
6
filtered replacement fluid.
7
Paired Filtration Dialysis Mid-dilution Haemodiafiltration
The paired filtration dialysis (PFD) technique is based on two filters placed The novel set-up of mid-dilution (MD)HDF consists of special filters with
in series. The first unit is a haemofilter (convection) and the second a two longitudinal compartments (see Figure 1H). Blood flow in the
haemodialyser (predominantly diffusion) (see Figure 1F). Replacement first compartment produces ultrafiltration and at the end of the
fluid is infused between the two units. This therapy minimises interaction compartment blood is redirected countercurrent into the second
between convection and diffusion and prevents backfiltration in the blood compartment. Blood leaves the dialyser alongside the arterial
EUROPEAN RENAL DISEASE 2007 55
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