Leypoldt JK, Cheung AK, Clark WR, Daugirdas JT, Gotch FA,
Greene T, Levin NW for the HEMO Study
Characterization of low and high flux dialyzers with reuse in
the HEMO study: Interim Report
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1518 1996
In the NIH HEMO trial, survival and hospitalization rate are being compared
in 4 groups of patients: URR about 67% and 75%, with each group
split evenly between high and low flux membranes. Flux is defined in terms
of beta-2-microglobulin clearance, and is targeted to be above 20 ml/min in
the high flux arm, and < 20 ml/min in the low flux arm.
Most centers in the United States are reusing dialyzers, and reuse, with
attendant use of large high efficiency dialyzers, which cannot be purchased
economically in a single use setting, is required to deliver the high URR
goal in a reasonable (< 4.5 hrs) amount of time to American-sized
patients. When setting up the trial, there was a lot of debate as to
whether or not only certain reuse methods should be allowed in the study.
The data with regard to beta-2-microglobulin clearance and reuse was
controversial; when bleach is used, b-2-M clearance goes up. When Renalin
is used (bleach is not normally used), b-2-M clearance was reported to go
down with some membranes, and to remain stable with others. The decision
was made to allow both bleach reuse and Renalin reuse in the trial, given
that we wanted the trial to be representative of dialysis as it was
currently prescribed, with the idea that b-2-M clearance would be closely
monitored during the trial to assure a good separation between groups.
Unmodified cellulose membranes were not allowed in the trial, as
biocompatibility questions would not be answered by the trial (both
bleach and non-bleach reuse methods were being allowed), and because it was
thought that by the completion date of the trial (2001), unsubstituted
cellulose membrane use would be small in the United States. Because of
concern of possible albumin loss (with bleach reuse) and loss of B-2-M
clearance (with non bleach reuse), the number of reuses in the HEMO trial
was limited to 20.
In the present study, Leypoldt et al report b-2-M (pre-post derived)
clearance data based on initial results, with the high (mostly F80 and
CT190) and low (mostly F8 and CA 170,210) flux membranes used in the trial.
One center is using heat, and the rest are more or less evenly split
between bleach reuse and Renalin reuse. Even under the constraints of a
maximum of 20 reuses, there was a good separation in b-2-M clearance in the
high and low flux groups (37 and 4 ml/min, respectively). However,
with bleach reuse, the b-2-M clearance was found to begin at a low level
and increase over time, whereas with Renalin reuse, b-2-M clearance
decreased over time. Using an (ad hoc) criterion of b-2-M clearance of 20
ml/min to designate a high flux dialyzer, it was found that by reuse 10-20,
neither F80 dialyzers nor CT-190 dialyzers could be classified as high
flux, as b-2-M clearance averaged about 10-15 ml/min under these
conditions. Furthermore,
Fresenius makes two classes of F80s: the F80B, designed for bleach reuse
(with a lower initial KUf), and the F80A, designed for Renalin (or non-
bleach resuse, with a higher initial KUf). On the initial few reuses, the
F80B dialyzers also have a b-2-M clearance that is lower than 20 ml/min.
These data suggest that, reuse of polysulfone or cellulose triacetate high-
flux dialyzers with Renalin (without bleach) results in degradation of
their high flux capacity. Also, Fresenius may have over-reacted to initial
reports of high protein losses with bleach reuse, and tightened up their
F80 bleach membrane a bit more than was needed. Certainly centers that are
not reusing with bleach should buy the F80A membrane.
These data are of course accessible to industry, and perhaps appropriate
corrective action will be taken, especially in terms of adjusting the KUf
of high flux dialyzers designed for bleach and non-bleach reuse.
The manufacturers of
Renalin believe they may be able to solve the problem of b-2-M clearance
decrease with reuse. Meanwhile, in the HEMO study, in response to these
results,
a decision has been made to attempt to limit reuse number to 10 in the
Renalin high flux group.
No matter what the HEMO
study finds and delivers in terms of b-2-M clearance for the high flux arm
of the trial (there is reasonable separation even now), there will always
be people (perhaps especially the Europeans who favor hemodiafiltration,
with
which b-2-M clearances > 60 ml/min can be regularly achieved) who will
criticize the trial, stating that a truly high flux therapy was not
delivered. On the other hand, we are doing this trial in the US, where
hemodiafiltration is not routinely practised, and where results need to be
obtained that are relevant to choices available here.
(John T. Daugirdas, M.D., University of Illinois at Chicago)
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Am Soc Nephrol
Basic hemodialysis :
Reuse, theory and practice
Basic hemodialysis :
Dialyzers