U.S. patent number RE36,914 [Application Number 09/250,449] was granted by the patent office on 2000-10-17 for dialysate filter including an asymmetric microporous, hollow fiber membrane incorporating a polyimide.
Invention is credited to Robert G. Andrus, Daniel B. Carlsen, Robert T. Hall, II.
United States Patent |
RE36,914 |
Carlsen , et al. |
October 17, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Dialysate filter including an asymmetric microporous, hollow fiber
membrane incorporating a polyimide
Abstract
A dialysate filter including asymmetric, microporous, hollow
fiber membranes incorporating a polyimide. The dialysate filter
connects to the dialysis machine immediately before the dialyzer
ensuring complete filtration of the dialysate, easy visual
inspection, quick installation and removal, and easy disinfection
of the filter.
Inventors: |
Carlsen; Daniel B. (Phoenix,
AZ), Andrus; Robert G. (Plymouth, MN), Hall, II; Robert
T. (Welch, MN) |
Family
ID: |
27369557 |
Appl.
No.: |
09/250,449 |
Filed: |
February 16, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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058904 |
May 6, 1993 |
5762798 |
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958027 |
Oct 7, 1992 |
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Reissue of: |
418802 |
Apr 7, 1995 |
05605627 |
Feb 25, 1997 |
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Current U.S.
Class: |
210/321.79;
210/257.2; 210/321.71; 210/321.8; 210/321.89; 210/500.23;
210/500.37; 210/500.39 |
Current CPC
Class: |
B01D
61/30 (20130101); B01D 69/02 (20130101); B01D
69/08 (20130101); B01D 71/64 (20130101) |
Current International
Class: |
B01D
61/24 (20060101); B01D 61/30 (20060101); B01D
71/00 (20060101); B01D 69/00 (20060101); B01D
69/08 (20060101); B01D 69/02 (20060101); B01D
71/64 (20060101); B01D 063/00 () |
Field of
Search: |
;210/321.6,321.79,321.71,321.8,645,500.23,500.37,500.39,321.65,321.89 |
References Cited
[Referenced By]
U.S. Patent Documents
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0082433 |
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Jun 1983 |
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EP |
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0125908 |
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Nov 1984 |
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EP |
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0422885 |
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Apr 1991 |
|
EP |
|
0446947 |
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Sep 1991 |
|
EP |
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0456143 |
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Nov 1991 |
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EP |
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0488018 |
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Jun 1992 |
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EP |
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2482468 |
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Nov 1981 |
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FR |
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2829630 |
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Jan 1974 |
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DE |
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2651818 |
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Jun 1977 |
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DE |
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3018667 |
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Nov 1981 |
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DE |
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3149976 |
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Jun 1983 |
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DE |
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59-230604 |
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Dec 1984 |
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JP |
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3-178324 |
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Dec 1987 |
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JP |
|
3-270721 |
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Dec 1991 |
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JP |
|
4-227831 |
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Aug 1992 |
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JP |
|
4-267934 |
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Sep 1992 |
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JP |
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8702924 |
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Dec 1987 |
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NL |
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2102333 |
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Feb 1983 |
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GB |
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Other References
C Dinarello, "Cytokines: Agents Provocateurs in Hemodialysis?",
Kidney International, vol. 41 (1992), pp. 683-694. .
"Quality Assurance for the '90s: A Bicarbonate Dialysate
Monography", Special Supp. to Neph. News & Issues, Jan. 1992.
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J. Bommer, et al., "No evidence for endotoxin transfer across high
flux polysulfone membranes", Clin. Neph., vol. 27, No. 6, 1987, pp.
278-282). .
S. Gordon et al., "Pyrogenic Reactions Associated with the Reuse of
Disposable Hollow-Fiber Hemodialyzers", JAMA, Oct. 14, 1988, vol.
260, No. 14. .
G. B. Harding et al., "Endotoxin and Bacterial Contamination of
Dialysis Center Water and Dialysate: a Cross Sectional Survey",
Intl. J. Artificial Organs, vol. 13, No. 1, 1990, pp. 39-43.. .
S. Gordon et al., "Pyrogenic Reactions in Patients Receiving
Conventional, High-Efficiency, or High-Flux Hemodialysis Treatments
with Bicarbonate Dialysate Containing High Concentrations of
Bacteria and Endotoxin", JASN, Mar. 1992, vol. 2, No. 9, pp.
1436-1444. .
S. Frinak et al., "Filtration of Dialysate Using an On-Line
Dialysate Filter", Intl. J. Artificial Organs, vol. 14, No. 11,
Nov. 1991, pp. 691-697. .
C. Mion et al., "Sterile and Pyrogen-Free Bicarbonate Dialysate: A
Necessity for Hemodialysis Today", Adv. Nephrol., 19:275-314, 1990.
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Dialysis, vol. 6, No. 1, (Jan.-Feb.) 1993, pp. 26-27. .
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American, Aug. 1992, 54-61. .
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Nephrology, Oct. 1991, pp. 20-22. .
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Dialysate", Dialysis & Translation, vol. 22, No. 3, Mar. 1993,
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Membranes: Small- Versus Large-Pore Membranes", Nephrol. Dial.
Transplant (1992), 7: 333-339. .
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English Abstract for EP-488018. (Corresponding non-English document
cited above.). .
English Abstract for JP Sho 59-230604 (Counterpart to U.S. Pat.
4,532,041). (Corresponding non-English document cited above.).
.
English Abstract for JP Hei 3-178324 (Counterpart to U.S. Pat.
5,015,270). (Corresponding non-English document cited above.).
.
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document cited above.). .
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.
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document cited above.)..
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Primary Examiner: Fortuna; Ana
Attorney, Agent or Firm: Wrigley; Barbara A.
Parent Case Text
This application is .Iadd.a reissue application of Pat. No.
5,605,627 which is .Iaddend.a continuation-in-part of application
Ser. No. 08/058,904 filed .[.Jun. 30, 1993, pending..]. .Iadd.May
6, 1993, U.S. Pat. No. 5,762,798, .Iaddend.which is a
continuation-in-part of application Ser. No. 07/958,027 filed Oct.
7, 1992, now abandoned. Both prior applications are incorporated by
reference herein, in their entirety.
Claims
We claim:
1. A filter comprising;
a housing defining an interior chamber;
an inlet port connected to said housing;
an outlet port connected to said housing;
an access port connected to said housing; and
a bundle of asymmetric, microporous, hollow fiber membranes
disposed within said interior chamber, said asymmetric,
microporous, hollow fiber membranes comprising a polyimide polymer,
said asymmetric, microporous, hollow fiber membranes including
pores having a pore size range from about 0.005 .mu.m to about 0.2
.mu.m, wherein said asymmetric, microporous, hollow fiber membranes
have a flux in excess of about 75.times.10.sup.-5
ml/(min.times.cm.sup.2 .times.mmHg); and
wherein said inlet port, said outlet port and said access port are
in fluid communication with said bundle of hollow fiber
membranes.
2. The filter of claim 1 wherein said fiber comprises 100 wt. % of
said polyimide polymer.
3. The filter of claim .[.2.]. .Iadd.1 .Iaddend.wherein said
polyimide polymer comprises a polymer having the structure:
##STR5## 10% to 90% of the R groups are ##STR6## and the remaining
R groups are ##STR7##
4. The filter of claim 3 wherein said fiber comprises from about
100 wt. % of said polyimide polymer.
5. The filter of claim 1 wherein said polyimide polymer comprises a
polymer having the structure:
6. The filter of claim 5 wherein said .[.fiber.]. .Iadd.polyimide
polymer .Iaddend.comprises from about 100 wt. % of said polyimide
polymer.
7. The filter of claim 2 wherein said polyimide polymer comprises a
polymer having the structure: wherein 10% to 90% of the R groups
are ##STR8## and the remaining R groups are ##STR9##
8. .[.The filter of claim 7 wherein said polyimide polymer
comprises from about 100 wt. % of said polyimide polymer..].
.Iadd.The filter of claim 2 wherein said polyimide polymer
comprises a polymer having the structure:.Iaddend.
9. The filter of claim 1 wherein said polyimide polymer has a
molecular weight of about 40,000 daltons to about 105,000
daltons.
10. The filter of claim 1 wherein said membranes are uniformly
porous throughout and wherein said membranes are characterized by
the absence of voids.
11. The filter of claim 1 wherein said membranes are capable of
being subjected to take-up rates in excess of 45 m/min during
manufacturing.
12. The filter of claim 1 wherein said membranes rewet by
maintaining a flux of at least 500 ml/(hr.times.m.sup.2
.times.mmHg) for six or more sterilizations and wherein said
asymmetric, microporous, hollow fiber membranes are further
characterized by having 0.0% wetting agent additives selected from
the group of hydrophilic polymers, nonionic, anionic, or amphoteric
surfactants.
13. The filter of claim 12 wherein said hydrophilic polymers
comprise polyvinylpyrrolidone.
14. The filter of claim 1 wherein the housing is a material
selected from polycarbonate, polyethylene or polypropylene.
15. The filter of claim 1 wherein the housing is polycarbonate.
16. A dialysis apparatus comprising:
a dialysis system comprising an artificial kidney operatively
connected to said dialysis system, said artificial kidney including
a dialysate inlet port;
a female to female connector; and
a dialysate filter, said dialysate filter comprising:
a bundle of asymmetric, microporous, hollow fiber membranes;
a filter housing defining an interior chamber;
a dialysate inlet port connected to said filter housing;
a dialysate outlet port connected to said filter housing;
a dialysate access port connected to said filter housing;
and said bundle of asymmetric, microporous, hollow fiber membranes
disposed within said interior chamber, said asymmetric microporous
hollow fiber membranes comprising a polyimide polymer, said
asymmetric, microporous, hollow fiber membranes including pores
having a pore size range from about 0.005 .mu.m to about 0.2 .mu.m,
and having a flux in excess of about 75.times.10.sup.-5
ml/(min.times.cm.sup.2 .times.mmHg); said dialysate inlet port,
said dialysate outlet port and said access port are in fluid
communication with said bundle of hollow fiber membranes; and
wherein the dialysate filter is located upstream of the artificial
kidney and is connected through the female to female connector to
the inlet port of said artificial kidney.
17. The dialysis apparatus of claim 16 wherein said filter is
connected directly to said female to female connector at the
dialysate inlet port of said artificial kidney.
18. .[.A.]. .Iadd.The .Iaddend.dialysis apparatus .[.comprising.].
of claim 16 wherein said filter is connected to said female to
female connector by a hose.
19. The dialysis apparatus of claim 16 wherein said fiber comprises
100 wt. % of said polyimide polymer.
20. The filter of claim 16 wherein said polyimide polymer comprises
a polymer having the structure: ##STR10## wherein 10% to 90% of the
R groups are ##STR11## and the remaining R groups are ##STR12##
21. The dialysis apparatus of claim 20 wherein said fiber comprises
from about 100 wt. % of said polyimide polymer.
22. The dialysis apparatus of claim 16 wherein said polyimide
polymer comprises a polymer having the structure:
23. The dialysis apparatus of claim 22 wherein said polyimide
polymer comprises from about 100 wt. % of said polyimide
polymer.
24. The dialysis apparatus of claim 16 wherein said polyimide
polymer has a molecular weight of about 40,000 daltons to about
105,000 daltons.
25. The dialysis apparatus of claim 16 wherein said membranes are
uniformly porous throughout and wherein said membranes are
characterized by the absence of voids.
26. The dialysis apparatus of claim 16 wherein said membranes are
capable of being subjected to take-up rates in excess of 45 m/min
during manufacturing.
27. The filter of claim 16 wherein said membranes rewet by
maintaining a flux of at least 500 ml/(hr.times.m.sup.2
.times.mmHg) for six or more sterilizations and wherein said
asymmetric, microporous, hollow fiber membranes are further
characterized by having 0.0% wetting agent additives selected from
the group of hydrophilic polymers, nonionic, anionic, or amphoteric
surfactants.
28. The dialysis apparatus of claim 27 wherein said hydrophilic
polymers comprise polyvinylpyrolidone.
29. The dialysis apparatus of claim 16 wherein the housing is a
material selected from polycarbonate, polyethylene or
polypropylene.
30. The dialysis apparatus of claim 16 wherein the housing is
polycarbonate .
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a dialysate filter which is
easy to install, durable and cost effective. In particular, the
invention relates to a dialysate filter which removes bacteria and
endotoxins from a dialysate stream before it enters an artificial
kidney. Still further, the dialysate filter of the present
invention includes improved asymmetrical, microporous, hollow
fibers incorporating a polyimide.
2. Description of the Related Art
A dialysate filter is a device which can be used in-line, between a
dialysis apparatus and an artificial kidney (dialyzer) during
hemodialysis treatments, to remove bacteria and endotoxins from the
dialysate stream. Endotoxins are potentially lethal
lipopolysaccharide (LPS) molecules which are released when
gram-negative bacteria disintegrate or are destroyed.
Endotoxins can cause Pyrogenic Reactions (PRs) in dialysis patients
either directly by passing through an artificial kidney membrane
into the patient's bloodstream, or indirectly, by inducing a
reaction across the artificial kidney membrane. PR(s) are one or
more symptoms caused by
exposure to endotoxins during dialysis, including fever, chills,
hypotension, headache, myalgia, nausea and vomiting. Symptoms
usually begin within 30-60 minutes after dialysis has begun, and,
vanish shortly after dialysis is stopped. Indirect PR(s) may occur
when endotoxins, while remaining trapped within the membrane, still
influence changes in a dialysis patient's bloodstream without
actually physically contacting the blood.
The role of endotoxins in the long-term morbidity and mortality of
dialysis patients is unclear; however, we do know that endotoxins
have the ability to stimulate monocytes to produce chemicals called
cytokines. These cytokines induce fever and catabolism in dialysis
patients. The present invention is a means for preventing PR's by
using sterile, non-pyrogenic dialysate during dialysis
treatment.
The prior art has promoted a number of alternatives for removing
endotoxins from dialysate. These alternatives include an artificial
kidney, ultrafiltration apparatuses, hemo-filters and in-line water
filters. These alternatives suffer from a number of disadvantages
including difficulty in use, expense and safety risks.
One significant safety risk of these modified devices is in the
event of a fiber rupture, the filter can release enormous
quantities of accumulated endotoxins into the dialysate stream.
This may present too large a challenge for the dialyzer to overcome
and the dialysis patient may suffer unpleasant consequences as a
result. Also, if a portion of this assumed-to-be sterile dialysate
solution is diverted and re-infused into the extracorporeal blood
circuit, as may be done in hemodiafiltration, then bacteria and
endotoxins may be injected directly into the patient's
bloodstream.
Previous studies have made claims to endotoxin free dialysate.
These claims may be not be completely accurate. Certain smaller
endotoxin fragments may be Limulus Amebocyte Lysate assay (LAL)
non-reactive. This means that much of the research done which has
used LAL to measure passage of endotoxins through dialyzer
membranes may be inaccurate. In other words, studies which claimed
that no endotoxin passes through dialyzer membranes and used LAL to
validate that claim may be inaccurate.
Also, there is some indication that certain smaller endotoxin
fragments may pass through conventional dialyzer membranes when
they may not pass through high flux membranes. This may be due to
differing membrane properties such as mechanisms of adsorption,
tortuous pathways, and ionic repulsion. In view of this endotoxins
are not merely a concern for high flux dialysis, but for
conventional and high efficiency dialysis also.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a dialysate
filter which solves the problems outlined above that inhibited
regular use of a dialysate filter, including difficult to use,
expense and safety risks. The dialysate filter of the present
invention enables the practitioner to quickly and easily install a
dialysate filter outside the housing of a dialysis apparatus and
thereby effectively monitor the filter and prevent dialysis machine
complications. Dialysis machine complications include restricted
dialysate flow, increased temperature and leaks. The dialysate
filter of the present invention works well with a variety of
dialysis machines and tolerates a wide variety of disinfecting
chemicals without loss of integrity.
The filter of the present invention includes a housing having an
inlet dialysate port, an outlet dialysate port and an access port
which function to allow air to be removed and a disinfecting agent
to be introduced. The housing contains an asymmetric microporous
hollow fiber membrane which incorporates a polyimide.
The filter of the present invention is .[.preferrably.].
.Iadd.preferably .Iaddend.a dialysate filter which is attached to a
dialysis apparatus. The dialysis apparatus includes a housing, a
dialyzer within the housing and a dialysate inlet port to the
dialyzer. The apparatus is connected with the dialysate filter
through a female to female connector. The filter is located
upstream of the dialyzer outside the housing.
The dialysate filter of the present invention creates dialysate
which is bacteria free and non-pyrogenic. The filter should be used
as a preventative measure or in the event of Pyrogenic Reaction, a
bacterial culture growth exceeding AAMI limits or a LAL assay
indicating that endotoxin levels are in excess of 5 EU/ml or 1
ng/ml.
These and other objects and advantages of the present invention
will become apparent during the course of the following detailed
description and appended claims. The invention may best be
understood with reference to the accompanying drawings, disclosure
and examples wherein an illustrative embodiment is shown.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a dialysis apparatus with a dialysate filter of the
present invention installed thereon.
FIG. 2 depicts a dialysate filter of the present invention and its
connectors.
FIG. 3A is an enlarged, microscopic, cross-sectional view of the
hollow fiber membrane in accordance with the present invention
illustrating the "homogeneous sponge-like" structure.
FIG. 3B is a greatly enlarged view thereof taken from the area
enclosed by box 3B in FIG. 3A.
FIG. 4 is an enlarged detailed view of the hollow fiber membrane in
accordance with the present invention illustrating the homogeneous
sponge-like structure taken at a 45.degree. angle of
cross-section.
FIG. 5A is an enlarged, microscopic cross-sectional view of prior
art hollow fiber membranes illustrating "voids."
FIG. 5B is a greatly enlarged detail view thereof taken from the
area enclosed by box 5B in FIG. 5A.
FIG. 6 is an enlarged, microscopic cross-sectional view of hollow
fiber membranes with voids.
FIG. 7 illustrates the pressure drop versus conductivity for a
polyimide filter.
FIG. 8 illustrates a comparison of pressure drop in water for a
variety of filters.
FIG. 9 illustrates a comparison of pressure drop in dialysate
between polyimide containing filters and polysulfone containing
filters.
DETAILED DESCRIPTION
The present invention is directed to a filter membrane, a dialysate
filter and a dialysis apparatus. Although the membrane and
dialysate filter are discussed in connection with their use in
dialysis, the skilled artisan would clearly recognize the
applicability of the membrane and filter to other technology areas.
These areas include water filtration, as a polishing filter for
pharmaceutical production, as a plasma filtering device, as a
chemofilter, as a hemoconcentrator, and the like.
Dialysate as used herein refers to the final solution, blended
within the dialysis apparatus, from sodium bicarbonate concentrate,
acid electrolyte concentrate, and ultra-pure water, which flows in
a single pass through the dialysate filter and artificial kidney
and then finally to drain.
An in-line filter, installed in the dialysate line of a dialysis
apparatus, will block passage of most endotoxins contained within
reverse osmosis water or the final dialysate stream of the dialysis
apparatus. The filter will prevent high loads of endotoxin from
reaching the dialysate compartment of the artificial kidney during
dialysis and causing Pyrogen Reactions in dialysis patients.
The filter membrane of the present invention produces a dialysate
which is bacteria free and non-pyrogenic. "Bacteria free" as used
herein means that no bacteria is detectable as determined by a
filter effluent sample's lack of bacterial growth in an optimum
environment for growth. "Non-pyrogenic" means that no endotoxins
are detectable as determined by the gel-clot method of Limulus
Amebocyte Lysate (LAL) assay of filtrate, or levels of pyrogenic
material are so low no PR will occur during dialysis. "Filtrate"
refers to the dialysate outflow or effluent from the filter.
The filter membrane of the present invention is particularly well
suited for these applications as it is easy to install, maintain
and sterilize. The filter membrane in one embodiment of the present
invention will tolerate a dialysate flow of from 300 ml/min to 1000
ml/min, and will also tolerate a wide variety of disinfection
regimens and chemicals.
As seen in FIG. 2, the dialysate filter of the present invention is
comprised of a housing (1) having a dialysate inlet port (2), a
dialysate outlet port (3) and an access port (4). Inside the
housing is a filter comprising a bundle of fibrous-membranes.
The housing can be made of any appropriate material which includes
polycarbonate, polypropylene, polyethylene, mixtures thereof and
the like. Preferably polycarbonate forms the housing.
The housing is connected to the dialysate inlet port on a dialysis
apparatus (5) through a female to female "Hansen" or "Walther"
connector (6). The connector (6) may be attached directly to the
dialysate outlet port of the filter (3) or may be connected via a
hose or other interposed connection means to the outlet port (3).
The connector (6) may take any shape but preferably is a
straight-line connect, a 45.degree. angle connect or a 90.degree.
angle connect. More preferably, the connector is a 90.degree. angle
connect.
The fiber membrane contained within the housing may be made of any
highly permeable filter medium, for example, polymeric fibrous
membranes. These membranes can be formed of polysulfone,
polycarbonate, polyimide and the like. The filter is preferrably
made up of asymmetric microporous hollow fiber membranes.
In one preferred embodiment of the present invention, the filter
contains asymmetrical microporous, hollow fiber membranes that
include a polyimide polymer that is highly polar. We define
microporous to mean membranes having a pore size ranging from about
0.005-0.2.mu.m. We also define "flux" or "water permeability" to
mean a measure of the volume of water passed by the hollow fiber
membrane under pressure for a given time and area. "Rewetting" and
similar words such as rewettable, rewettability, etc., as used
herein, is a description of the ability of a membrane to maintain a
particular level of flux or water permeability after either cycles
of wetting and drying the membrane or after steam or chemical
sterilization. "Asymmetric" means that the pore size of the fiber
varies from smaller to larger from the inner barrier layer to the
outer sponge-like layer, respectively. "Uniformly porous" and
"sponge-like" means that the porosity of the hollow fiber membrane
is homogeneous throughout. In addition, "solvents with respect to
the polymer" are typically aprotic solvents while "non-solvents
with respect to the polymer" are typically protic solvents.
"Anti-solvent" is a nonsolvent with respect to the polymer and is
used herein when referring to additional nonsolvents that are added
to the polymeric solution. "Nonsolvents," on the other hand, are
also nonsolvents with respect to the polymer, but is used herein
when referring to nonsolvents added to the precipitating
solution.
The highly polar polymer in accordance with the present invention
is preferably an aromatic polyimide that when precipitated as a
membrane is immediately wettable without the use of polymer
additives or surfactants. The preferred polyimide in accordance
with the present invention is disclosed in U.S. Pat. No. 3,708,458
to Alberino which is incorporated herein by reference, in its
entirety. The polyimide is prepared from
benzophenone3,3',4,4'tetracarboxylic acid dianhydride and a mixture
of 4,4' -methylenebis(phenylisocyanate) and toluene diisocyanate
(2,4- or 2,6-isomer) or mixtures thereof. The polyimide includes
the recurring group: ##STR1## wherein 10% to 90% of the R groups
are ##STR2## and the remaining R groups include either ##STR3##
The aromatic iso- and diisocyanates may be substituted by their
amine analogs. The CAS Registry No. of the preferred polyimide is
58698-66-1. The polyimide is available from Lenzing Corp. (Austria)
under the P84 and/or HP P84 (high purity) marks. In an alternative
embodiment, a polymer based on the phenylindane diamine;
5(6)-amino-1-(4'-aminophenyl)-1,3-trimethylindane with a CAS
Registry No. of 62929-02-6 may be used. The alternative embodiment
polymer is available from Ciba-Geigy Corporation (Hawthorne, N.Y.)
under the Matrimid 5218 mark.
The structure of the polymer repeating unit is believed to consist
of: ##STR4##
The alternative preferred embodiment may be prepared by the methods
disclosed in U.S. Pat. No. 3,856,752.
The polyimide polymers useful in accordance with the present
invention preferably have a molecular weight of about 30,000 to
125,000 daltons. More preferably, the molecular weight is about
35,000 to 115,000 daltons and most preferably, the molecular weight
is about 40,000 to 105,000 daltons.
As stated previously, no additional additives, such as
polyvinylpyrrolidone, polyethylene glycol, glycerine, cellulose or
starch derivatives or amphoteric, zwitterionic, nonionic, anionic,
or cationic surfactants, are needed to produce a hollow fiber
membrane that wets immediately upon contact with dialysate, blood,
water and other aqueous solutions and maintains the rewettability
for at least 6-7 sterilizations by steam or chemicals. Because no
additional polymers are needed to make the resultant fiber
wettable, the choice of solvents, including nonsolvent combinations
at specific ratios, for use as the precipitating solution is
critical in influencing the hydrophilicity, structure and porosity
of the fiber. In addition, the elimination of additives in the
polymeric dope solution decreases and virtually eliminates all but
trace amounts of solids and/or oxidizable material that is
leachable from the resultant fiber. Further, the structural
integrity of the resultant hollow fiber membrane is more stable
after the removal of the solvent and/or antisolvents and
nonsolvents.
Initially, the polyimide polymer is dissolved in a solvent
including solvent/antisolvent combinations. Preferably, this
solvent is also miscible with water. A representative, non-limiting
list of solvents useful in the invention includes dimethylformamide
(DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA),
n-methylpyrrolidone, and mixtures thereof. Preferably, the solvent
is DMF, an aprotic solvent. Depending on the desired properties of
the hollow fiber, a small amount of an antisolvent may be added in
small quantities to the primary solvent that is used. The addition
of an antisolvent in the polymer forming solution will enhance the
desired precipitate characteristics of the polymer during fiber
formation. For example, adding acetic acid in the amount of 4-7 wt.
% ensures that the fiber has a uniform sponge-like structure, free
of voids, large vacuous spaces extending from the inner membrane
wall to the outer membrane wall that can permit the passage of
large molecular weight molecules if the void pierces the inner
and/or outer membrane wall. Alternatively, additional amounts of
solids may be added to the polymer solution up to 25.0 wt. % to
solve this problem. The homogeneous, sponge-like structure may also
be achieved in accordance with the process and formulations
described herein.
FIG. 3 depicts a cross section of a hollow fiber membrane in
accordance with the present invention magnified 130.times. taken on
a Hitachi 5-800 scanning electron microscope. FIG. 3B which is a
10.times. magnification (1300.times.) of the area enclosed by box
4B in FIG. 3A and illustrates the "uniform sponge-like structure
200 of hollow fiber membranes in accordance with the present
invention. FIG. 4 is a 10,000.times. view taken at a 45.degree.
angle of cross-section of hollow fibers in accordance with the
present invention showing the outer membrane wall 210 and the
sponge-like inner composition 215. "Voids" 220, which characterize
many hollow fiber membranes, may be seen by referring to FIGS.
5A
(130.times.) and 5B (1300.times.). The absence of voids in the
formed hollow fiber membrane results in a mechanically stronger
fiber with enhanced diffusion rates.
Preferably, about 15-25 wt-%, more preferably, about 16-20 wt-%,
and most preferably, about 17-19 wt-% of the fiber forming
polyimide polymer is dissolved in the dimethylformamide solvent.
When less than 15 wt-% of the polyimide polymer is used, the fibers
formed may not be strong enough to withstand the stresses involved
in the high speed process in the preferred method of manufacturing
the fiber membrane used in the present invention. Further, the
fibers lack integrity due to the weakness from the voids in the
fiber walls.
Higher polyimide solids may be employed in organic solvent systems
if spinerette housings, feed lines, polymer solution tanks are
heated. Upon heating, the viscosity of the polymer solution is
lowered, allowing otherwise unusable polymer solution formulations
to be spun. Depending upon the composition of the precipitating
solution the skilled practitioner chooses, heating and/or cooking
the system may influence the morphology and performance
characteristics of the resultant fiber membrane.
The polymeric solution has a viscosity of about 1500-5000 cps,
preferably about 2000-4000 cps, and most preferably about 3600 to
4900 cps at 25.degree. C., as measured on a Brookfield (LV)
viscometer. The solution is preferably filtered to remove any
entrained particles (contaminants or undissolved components) to
prevent apparatus blockage.
The polymeric solution is spun from the outer, annular orifice of a
tube-in-orifice spinerette. A precipitating solution is delivered
to the tube of the spinerette. The precipitating solution includes
a solvent with respect to the polymer and a non-solvent with
respect to the polymer or a variety of non-solvents. The
composition of the precipitating solution is critical because it
affects the porosity, degree of uniform sponge-like structure,
clearance, tensile strength, wall thickness, inner and outer
diameters and flux properties of the fiber.
For example, as the weight percent of the solvent with respect to
the polymer increases, fiber formation is impaired and is
characterized by a "glassy" weaker structure and it becomes
increasingly difficult to "pull" the fiber. Conversely, as the
weight percent of the solvent with respect to the polymer decreases
and the weight percent of water and/or other non-solvents with
respect to the polymer increases, voids are seen in the fiber
structure which may allow high molecular weight molecules to pass
through the fiber if they pierce the outer membrane wall. This may
best be seen in FIG. 6 which illustrates a fiber cross-section
magnified 130.times. with voids 221 that resulted from using a
precipitating solution with an increased weight percent of
non-solvent with respect to the polymer. In addition, as the weight
percent of water and/or other non-solvents with respect to the
polymer increases, a low pore density on the outer fiber wall and a
tighter closed inner wall with a low flux is seen. It will
therefore be appreciated by those skilled in the art that the
selection of the composition of the precipitating solution is
crucial.
The composition of the precipitating solution effective to produce
a hollow fiber membrane for use in hemodialysis, as well as, water
filters, autologous blood filters, and plasma filters is
illustrated below in Table I.
TABLE I ______________________________________ More Most Preferred
Preferred Preferred ______________________________________ Solvent
with 50-99 wt. % 60-95 wt. % 75-90 wt. % respect to polymer Water
35-1 wt. % 30-5 wt. % 20-10 wt. % Add'l Non-Solvents 15-0 wt. %
10-0 wt. % 5-0 wt. % with respect to polymer
______________________________________
The table above is merely offered to guide the practitioner in
formulating precipitating solution. Indeed, the practitioner may
decide that it is advantageous to operate in a "Preferred" range
for one component while operating in a "Most Preferred" range for
another. In addition, depending on which formulation of
precipitating solution the practitioner selects, he or she may also
vary the percent solids in the polymer solution to obtain a fiber
of the desired characteristics.
The water which may be used in the precipitating solution may be
tap water, deionized water or water which is a product of reverse
osmosis. Preferably the water has first been treated by reverse
osmosis.
As stated previously, the solvent (with respect to the polymer)
used in the precipitating solution is dimethylformamide (DMF),
dimethylsulfoxide (DMSO) dimethylacetamide (DMA),
n-methylpyrrolidone and mixtures thereof. Preferably, the solvent
is the same as that used in the polymeric fiber forming solution.
More preferably, the solvent is DMA or DMF. Most preferably, the
solvent is DMF.
Additional combinations of solvents and non-solvents, which may or
may not contain salts, may be used so long as they are miscible
with dimethylformamide, dimethylsulfoxide, dimethylacetamide,
n-methylpyrrolidone and mixtures thereof. A representative,
non-limiting list of non-solvents (with respect to the polymer)
that may be used in the precipitating solution are acetic acid,
isopropanol, water, glycerol, acetic anhydride, and ethanol.
The proportions of the water, and other non-solvents (e.g. alcohol)
which may make up the precipitating solution influence the
morphology, clearance, permeability, and selectivity
characteristics of the hollow fiber membrane. In particular, the
total absence of a solvent with respect to the polymer in the
precipitating solution may result in a small number of pores in the
fiber wall as well as lower flux. Further, water is clearly an
important ingredient in the precipitating solution used in this
membrane formation process.
Because the addition of water affects the performance
characteristics of the resultant fiber membrane it is generally
preferred that the proportion of water in the precipitating
solution be about 1-35 wt. %, to ensure proper fiber performance
characteristics. Less than about 10 wt. % of water may result in
the polymeric solution precipitating too slowly forming a fiber
with increased pore size. This is desirable to form a fiber for use
in water filters but would not, for example, form a fiber suitable
for use as a dialyzer fiber. Conversely, a concentration of water
greater than about 35 wt. % results in a fiber with lower pore
density on the outside and a tighter closed inner wall with a
general decrease in flux. However, when the proportion of water
falls within 1-35 wt. %, we see enhanced uniformity in the
desirable sponge-like structure and the hollow fiber membrane is
characterized by the complete absence of voids. This uniformity
results in more overall uniform flux with respect to all types of
filters and tighter controls with respect to molecular weight
cutoffs in dialyzer applications.
The hollow fiber membranes may be formed using tube-in-orifice
spinning procedures as disclosed in the .[.copending.].
.Iadd.abandoned.Iaddend., commonly assigned applications Ser. No.
07/684,585, filed Apr. 1, 1991 entitled "Improved Fiber Spinning
Process for the Preparation of Asymmetrical Microporous Hollow
Fibers" and Ser. No. 07/902,389, filed Jun. 23, 1992 entitled
"Hollow Fiber Membrane Incorporating a Surfactant and Process for
Preparing Same," the disclosures of which are hereby incorporated
by reference.
Initially, the highly polar polymer is diluted in DMF. Depending on
the desired properties and characteristics of the hollow fiber, a
small amount of a non-solvent (with respect to the polymer) (also
called anti-solvents) other than water may be added instead of
using pure DMF solvent. This may enhance the precipitation of the
polymer in the fiber formation. For example, the addition of 4-7
wt. % glacial acetic acid to the polymer/DMF solution enhances the
uniform sponge-like structure of the resultant fiber and the fiber
is further characterized by the complete absence of voids.
The polymeric dope solution is pumped, filtered and directed to the
outer, ring orifice of a tube-in-orifice spinerette. At the same
time, the precipitating solution is pumped to the inner coaxial
tube of the spinerette. These two solutions are then delivered from
the spinerette in a manner such that the polymer dope forms an
annular sheath surrounding a flow of precipitating solution within
the annulus. Preferably, the spinerette head is maintained at a
temperature of about 5.degree.-85.degree. C., more preferably,
about 15.degree.-25.degree. C., and most preferably,
23.degree.-24.degree. C. The 23.9.degree. C. polymeric dope is
subjected to a pressure of about 0-1400 kPa, more preferably, about
140-1000 kPa, and most preferably, about 150-750 kPa. In a
preferred embodiment, the polymer dope is spun through a ring
orifice having an outside diameter of about 0.018 to 0.040 inches
(about 460 to 1,016 microns) and an inside diameter of about 0.008
to 0.010 inches (about 200 to 280 microns).
At the same time, precipitating solution is pumped through the tube
of the spinerette at a pressure of about 0-1000 kPa, preferably
about 0-100 kPa, and most preferably, about 1-20 kPa. In a
preferred embodiment, the precipitating solution or diluent
solution is delivered through a tube having an outside diameter of
substantially about 0.010 inches (about 254 microns) and an inside
diameter of substantially about 0.004 to 0.005 inches (about 100 to
127 microns).
In a preferred embodiment, in order to produce a hollow fiber
having an approximately 190-230 micron inside diameter and a wall
size of 30-45 microns, the polymer dope is delivered to the
spinerette at a rate of substantially about 1.0-10 mL/min, more
preferably, about 2-5 mL/min, most preferably, about 3-4.5 mL/min,
and the precipitating solution is delivered at a rate of at least
about 1.0-10 mL/min, more preferably, about 2-5 mL/min, and most
preferably, about 2-3 mL/min. The spinerette is oriented in a
manner such that fiber production is driven by fluid flow and by
removal from the spinerette by gravity effects. Preferably, the
fiber emerges from the spinerette and is pulled by gravity and the
take-up speed in a nearly vertical direction downwards.
In order to provide satisfactory fibers in the practice of the
invention, laminar fluid flow should be maintained both within the
spinerette head for the polymeric solution and the precipitating
solution which interact to precipitate the formed fiber. If
turbulent flow is present in the spinerette head, especially within
the channels which convey the polymeric dope, gas pockets may
develop and ultimately form large voids in the spun fiber.
Turbulent flow-within the spun fluids may also result in voids
within the fiber.
It is helpful to visualize the spinerette dimensions by resort to
ratios of the annular orifice for passage of the polymeric dope and
the coaxial tubular orifice for passage of the diluent or
precipitating solution. One helpful ratio is the ratio of the
cross-sectional area of the annular orifice to tubular orifice.
Preferably, the ratio is greater than about 1:1, more preferably,
the ratio is about 3:1 to 25:1, and most preferably, the ratio of
the annular orifice to tubular orifice cross-sectional area is
about 4:1 to 15:1.
Another helpful dimensional ratio is the annular ring thickness to
tube inside diameter. Preferably, the ratio is greater than about
1:1, more preferably, the ratio is about 1.5:1 to 7:1, and most
preferably, the ratio of the annular ring thickness to tube inside
diameter is about 2:1 to 6:1.
A third helpful dimensional ratio is the outside diameter of the
annular orifice to tube inside diameter. Preferably, this ratio is
greater than about 2:1, more preferably, the ratio is about 3:1 to
10:1, and most preferably, the ratio of the annular outside
diameter to tube inside diameter is about 4:1 to 8:1.
As the fiber emerges from the spinerette, it drops in a
substantially downward vertical direction over a distance of about
0.1-10 m, more preferably, about 0.5 to 2.0 m, and most preferably,
about 0.5 to 1.5 m. This allows the precipitating solution to
substantially precipitate the polymer in the annular dope solution
forming the solid fiber capillary before it is immersed in a
quenching solution. Between the spinerette and the quenching bath,
the fiber drops through the atmosphere, air, air with a particular
relative humidity, an augmented atmosphere, e.g., a mixture of air
or air with a particular relative humidity and a gas, an inert gas,
or a mixture thereof. Preferably, for ease in processing and to
produce a high quality fiber, the fiber drops through air
maintained at a temperature of 0.degree. C. to 100.degree. C., more
preferably, the air is maintained at a temperature of 5.degree. C.
to 50.degree. C. and most preferably at 15.degree. C. to 25.degree.
C. Preferably the air is also maintained at a relative humidity of
substantially about 10% to 99%, more preferably from substantially
about 20% to 80% and most preferably from substantially about 40%
to 65%. This gaseous atmosphere may be relatively stagnant, or
there can be fluid flow. Preferably, the flow rate is sufficient to
allow complete air change over in the spinning environment once
every 30 minutes. In one preferred embodiment, the gas flow is
about 10 L/min. In an alternative embodiment, the fiber may be
dropped directly into the quenching bath.
The fiber is submerged in a tank comprising water and 0-10 wt. %
other materials. Again, the water may be tap, or any purified water
including deionized water, or the product of a reverse osmosis
process. The temperature of the quenching bath is preferably
between about 0.degree. C. to 100.degree. C., more preferably,
about 15.degree. C. to 45.degree. C., and most preferably, about
35.degree. C. The water temperature directly affects-the
performance of the fiber. Lower temperatures can reduce the flux of
the resulting fiber. Increasing the quenching bath temperature can
increase the flux of the fiber.
The fiber is preferably immersed in the quenching bath for a period
of about 0.1 to 10 seconds, preferably about 0.1 to 5 seconds, and
most preferably, about 1 second. This residence time permits the
full precipitation of the polyimide polymer to form the microporous
hollow fiber.
After the quenching bath, the fiber may be further rinsed to remove
any remaining solvents. This rinsing may be accomplished in a water
bath arrangement. Preferably, the additional rinse is achieved in a
water bath having a water temperature of about 0.degree.
C.-100.degree. C., more preferably, about 15.degree. C.-45.degree.
C., and most preferably, about 35.degree. C. The fiber is then
wound on a take-up reel. The take-up reel is preferably rotating at
a speed such that the fiber is being wound at about 90-175% of the
rate at which it is being formed at the spinerette or, in other
words, at approximately about 150-250 ft/min (about 45-77 m/min).
More preferably, the fiber is being wound at a rate substantially
equal to that at which it is being produced. In other words, the
fiber is taken up with enough speed (i) to create a fiber of the
desired size and (ii) to apply sufficient tension to the fiber such
that it will remain taut in the take-up guide unaffected by ambient
air currents, i.e. there is no "draft."
The hollow fibers may then be dried by any method appropriate to
general manufacturing procedures including but not limited to air,
heat, vacuum, or any combination thereof. The hollow fibers may be
further processed to form useful articles including hemodialyzer
cartridges, hemofilters, blood filters, water filters, etc., having
improved performance levels.
In the present invention, polyimide fibers are preferred over
polysulfone because they have a lower pressure drop across the
filter, i.e., they are more permeable.
The filter of the present invention preferably contains a bundle of
fibers
which are anchored within the housing by a potting composition. The
preferred potting composition of the present invention is urethane.
The fiber bundle within the housing should contain sufficient
fibers to achieve the objectives of the filter as disclosed,
however, the skilled practitioner would understand that the number
of fibers may be modified so that the necessary permeability of the
filter is maintained. The number of fibers is preferably between
4500 and 5000 fibers per bundle.
As described above, the filter of the present invention is
preferably attached via a Hansen connector. In one preferred
embodiment, the filter is attached to the dialysis apparatus at the
inlet dialysate port outside the housing immediately upstream of
the artificial kidney or dialyzer.
The filter of the present invention may be installed within the
dialysis apparatus housing, however, it will be more difficult to
clean and evaluate based upon that location. The filter may also be
placed further upstream of the dialyzer, however, upstream
placement runs an added risk of recontamination of dialysis
fluids.
By placing the filter outside the housing, the pressure drop across
the filter can be easily monitored. The pressure drop is indicative
of flow characteristics of the dialysate and can indicate dialysis
machine complications, including restricted flow, leaks, or an
increase in temperature. With the external placement of the filter
in the preferred embodiment of the present invention, the filter
may be installed or replaced while a dialysis treatment is ongoing.
Accordingly, in the event of a rupture of the filter, the unit can
be quickly and easily replaced without any added risk to the
patient.
The filter can be used with any hemodialysis machine but is
preferably used with single pass ultrafiltration controlled
hemodialysis machines.
The preferred dialysate filter of the present invention has the
properties set forth in the Table below:
TABLE II ______________________________________ Fiber Hydrophilic
Polymer Number of Fibers 5000 Effective Surface Area 0.3 m.sup.2
Initial Pressure drop 60 mmHg (in dialysate) (Q = 500 ml/min)
Maximum Pressure Drop 160 mmHg (in dialysate) Total Fluid Volume 72
ml Overall Unit Length 192 mm Unit Weight (Dry) 145 g Outer Case
Material Polycarbonate Potting Compound Polyurethane O-Ring
Silicone Dialysis Fluid Connectors Hansen or Walther Connectors
______________________________________
The filters should be stored between 0.degree. and 35.degree. C.,
and excessive changes in humidity should be avoided.
The filter of the present invention should be disinfected daily.
Preferred disinfectants include acetic acid based sterilants
available under the tradenames Actril and Renalin Cold Sterilant,
bleach and heat treatment. The filter is replaced preferably within
30 days. The filter should also be replaced in the event the
pressure across the filter rises or drops to unacceptable levels.
Preferably, the filter is replaced if the pressure drop across the
filter is greater than 155 mmHg (3 PSI) or less than 52 mmHg (1
PSI).
EXAMPLES
The following specific examples which contain the best mode, can be
used to further illustrate the invention. These examples are merely
illustrative of the invention and do not limit its scope.
Examples 1-7 characterize and describe how to prepare the polyimide
fibers according to one preferred embodiment of the present
invention. Examples 8-29 describe the preparation, testing,
cleaning and use of the filters of the present invention.
Example 1
A polymeric dope solution was formed by dissolving 17.5 wt. % of
P84 in dimethylformamide. The material was filtered and then pumped
to a tube-in-orifice spinerette at a rate of 4.50 mL/min and at a
temperature of 24.degree. C. Simultaneously, a precipitating
solution consisting of 80 wt. % dimethylformamide and 20 wt. %
reverse osmosis deionized water was mixed, filtered and delivered
to the spinerette at a temperature of 24.degree. C. and a rate of
2.75 mL/min.
The polymeric dope solution was delivered through the outer,
annular orifice of the spinerette, which orifice had an outside
dimension of about 0.022 to 0.025 inches (about 560 .mu.m) and an
inside dimension of about 0.010 inches (about 254 .mu.m). The
precipitating solution was delivered through a tube-in-orifice
within the annular orifice, which tube-in-orifice had an inside
diameter of about 0.005 inches (about 127 .mu.m). The spinerette
head was maintained at 24.degree. C. The spinerette discharged the
polymeric solution and precipitating solution downward into ambient
atmosphere for a distance of about 1.5 meters into a quenching bath
maintained at 32.degree. C. Formed fiber material was wound on a
take-up reel at a rate of 70 m/min. The fiber was then removed from
the take-up wheel, cut, bundled, soaked in a water bath at
32.degree. C. for 10 hours, dried and tested.
Test Data #1
Fiber membranes prepared by the method recited in Example 1 had
sieving coefficients of 0.0 for albumin, 1.0 for myoglobin and 1.0
for inulin.
______________________________________ Phos- Cytochrome Blood Fl.
Urea Creatinine phorous B-12 C
______________________________________ 200 mL/m 179.4 164.9 156.5
87.4 129.9 300 mL/m 225.0 198.5 182.6 93.8 143.0 400 mL/m 244.8
212.5 208.7 95.7 146.8 ______________________________________
Example 2
The method for preparing fiber as in Example 1 was repeated using a
precipitating solution of 81 wt. % DMF and 19 wt. % deionized
water.
Test Data #2
Resultant fiber membranes had sieving coefficients of 0.0 for
albumin, 1.0 for myoglobin, and 1.0 for inulin.
______________________________________ Phos- Cytochrome Blood Fl.
Urea Creatinine phorous B-12 C
______________________________________ 200 mL/m 188.1 178.3 166.7
88.5 156.9 300 mL/m 249.6 223.4 212.5 95.4 178.7 400 mL/m 281.5
246.7 233.5 116.0 184.0 ______________________________________
Example 3
The method employed in Example 1 was repeated using 17.0 wt. % of
the P84 polyimide polymer and 83 wt. % DMF. The precipitating
solution comprised 81 wt. % DMF and 19.0 wt. % deionized water.
Sieving-coefficients were similar to the Test Data obtained for
Examples 1 and 2 above.
______________________________________ Phos- Cytochrome Blood Fl.
Urea Creatinine phorous B-12 C
______________________________________ 200 mL/m 190.7 178.4 166.7
-- 162.9 300 mL/m 255.2 232.45 228.0 -- 185.7 400 mL/m 287.3 256.9
240.0 -- 188.8 ______________________________________
Example 4
Fibers for use in a water filter were manufactured in the following
manner. A polymeric dope solution was formed by dissolving 19.0 wt.
% of Matrimid 5218 in 81.0 wt. % DMF. The material was filtered and
then pumped to a tube-in-orifice spinerette at a rate of 2.9 mL/min
at a temperature of 23.degree. C. Simultaneously, a precipitating
solution consisting of 85.5 wt. % DMF and 14.5 wt. % water was
mixed, filtered and delivered to the spinerette at a temperature of
23.degree. C. and a rate of 3.0 mL/min.
The polymeric dope solution was delivered through the outer,
annular orifice of the spinerette having an outside diameter of 940
.mu.m and an inside diameter of 254 .mu.m. The precipitating
solution was delivered through a tube-in-orifice within the annular
orifice having an inside diameter of about 127 .mu.m. The
spinerette head was maintained at about 23.degree. C. The
spinerette discharged the column of polymeric/solution and
precipitating solution downward for a distance of about 0.81 m into
a quenching water bath maintained at a temperature of 35.degree. C.
The fiber was wound on a take-up reel at a rate of about 45 m/min.
Cut bundles were soaked in a 46.degree. C. water bath for 16 hours.
Fiber bundles were dried and tested. Based on a 0.05 m.sup.2 test
mat, at 5 psi, water permeability was calculated to be 500
mL/(hr.times.m.sup.2 .times.mmHg).
Example 5
Fibers for use in a plasma filter were manufactured in the
following manner. The method for preparing fiber as in Example 4
was repeated using a polymeric dope solution consisting of 16.75%
P84 polymer and 83.25 wt. % DMF. The precipitating solution
included 85.5 wt. % DMF and 14.5 wt. % deionized water. Fibers had
a sieving coefficient of 0.65 using a 0.1% solution of fluorescein
isothiocyanate dextran (Sigma), a molecular weight marker of
approximately 500,000 Daltons. Water permeability was in excess of
900 (mL/hr/mmHg/m.sup.2).
Example 6
Fibers for use in a water filter were manufactured in the following
manner. A polymeric dope solution was formed by dissolving 16.75
wt. % P84 polymer in 83.25 wt. % DMF. The material was filtered and
then pumped to a tube-in-orifice spinerette at a rate of 4.5 mL/min
at a temperature of 23.degree. C. Simultaneously, a precipitating
solution consisting of 85.5 wt. % DMF and 14.5 wt. % water was
mixed, filtered and delivered to the spinerette at a temperature of
23.degree. C. and a rate of 3.0 mL/min.
Fibers were further processed in accordance with the method of
Example 4. .[.Fibers were further processed in accordance with the
method of Example 4..]. A water filter (1.5 m.sup.2 of fiber)
containing the fibers manufactured using the above formulation was
tested for water permeability. At 8.6 psi, filters had a water
permeability of 1020 ml/(hr.times.m.sup.2 .times.mmHg). At 10.0
psi, filters had a water permeability of 1320 ml(hr.times.m.sup.2
.times.mmHg).
Example 7
Fibers for use in water filters were prepared in the following
manner. A polymeric dope solution was formed by dissolving 15.2 wt.
% P84 polyimide polymer in 79.80 wt. % DMF and 5.0 wt. % glacial
acetic acid. The material was filtered and pumped to a
tube-in-orifice spinerette at a rate of 4.1 mL/min. A precipitating
solution comprised of 50 wt. % DMF and 50 wt. % glacial acetic acid
was mixed, filtered and delivered to the spinerette at a rate of
4.5 mL/min.
The polymeric dope solution was delivered through the outer,
annular orifice of the spinerette having an outside dimension of
about 0.029 inches (737 .mu.m) and an inside dimension of about
0.01 inches (about 254 .mu.m). The precipitating solution was
delivered through a tube-in-orifice within the annular orifice
having an inside diameter of about 0.005 inches (about 127 .mu.m).
Precipitated fiber was quenched in a reverse osmosis water bath and
taken up at a rate of 49 m/min.
Water Permeability
All fibers produced in the Examples above were evaluated for water
permeability (flux) in the following manner. Water was passed
through the lumens of potted test fibers with the filtering unit in
a horizontal position. The ultrafiltrate port on the inlet side of
the unit was plugged. Pressure monitors were placed at all inlet
and outlet ports. With flow through the unit, back pressure was
applied to the fiber outlet side of the unit to increase
ultrafiltrate flow across the fibers. Three data points were taken
at 10%, 50%, and 80-100% ultrafiltrate flow and transmembrane
pressure (TMP) was calculated. Ultrafiltrate flow gas plotted
against TMP and the slope of this curve was used to determine flux
or water permeability. As noted above, all of the above fibers for
use as water filters, hemofilters and dialyzers had water
permeabilities in excess of 75.times.10.sup.-5
ml/(min.times.cm.sup.2 .times.mmHg).
Example 8
A dialysate filter was prepared by spinning hollow fibers
incorporating a polyimide. The dried fiber bundles were inserted
into the molded polycarbonate case. Special potting caps were
placed at the ends of the molded polycarbonate case. The ends of
each fiber were cut to size. Urethane potting material was then
centrifugally placed in the case to seal the fibers to the case.
Excess potting material was cut away to expose the ends of the
fibers and provide a fluid flow path in the completed dialysate
filter. Once the ends of the filter were potted and cut,
polycarbonate headers fitted with an O-ring were placed on the ends
of the case. A cap was placed over the access port. One end of the
filter was resealed with urethane so that the dialysate only had
one outlet from the unit. The unit's maximum levels of residuals
were 25 ppm for ethylene oxide, 25 ppm for ethylene chlorohydrin
and 250 ppm for ethylene glycol. The unit was packaged in a sealed
Tyvek pouch. The filter had the following properties:
TABLE III ______________________________________ Fiber Hydrophilic
Polymer Number of Fibers 5000 Effective Surface Area 0.3 m.sup.2
Initial Pressure drop 60 mmHg (in dialysate) (Q = 500 ml/min)
Maximum Pressure Drop 160 mmHg (in dialysate) Total Fluid Volume 72
ml Overall Unit Length
192 mm Unit Weight (Dry) 145 g Outer Case Material Polycarbonate
Potting Compound Polyurethane O-Ring Silicone Dialysis Fluid
Connectors Hansen or Walther Connectors
______________________________________
A NEO-1 Dialysate Meter from Automata Medical Instrumentation Inc.
in Arizona measured conductivity upstream and downstream of the
dialysate filter described above. The meter contains a flow-through
conductivity cell having a temperature sensor for temperature
compensation. The cell attached to the dialysate lines with
Hansen.RTM.-style fittings.
Conductivity readings pre- and post the dialysate filter were
stable and did not vary more than .ltoreq.2%.
Example 9
The electrolyte composition was analyzed at the filter inlet and
outlet for a dialysate filter as described in Example 8. The
dialysate filter was installed on a Travenol 450 SPS dialysis
machine between the dialyzer-inlet and dialyzer-outlet lines. A
throughput flow at 600 ml/min was initiated and concentrate uptake
lines were connected to sterile, non-pyrogenic liquid bicarbonate
and acid electrolyte concentrate containers. Concentrates were
diluted internally by the Travenol 450 SPS using reverse osmosis
water meeting the AAMI standards for water used to make
dialysate.
The dialysate conductivity was allowed to stabilize as indicated by
a conductivity reading taken at the filter inlet stream. We also
waited until the machine issued no dialysate-related alarm
conditions, including over-pressure, temperature varying from
37.degree..+-.2.degree. C. Throughput of the dialysate at 600
ml/min was continued for 30 minutes. Using a "clean-catch"
technique, samples of at least 200 ml/min were collected at the
filter inlet and outlet in acid washed polyethylene bottles. These
bottles were sent to an outside laboratory for testing. The results
of the tests were as follows:
TABLE IV ______________________________________ Dialysate Within
Analyte Unfiltered Filtered .+-.2% VAR VAriance
______________________________________ Sodium 135 mEq/L 133 mEq/L
132.3- Yes 137.7 Potassium 1.9 mEq/L 1.9 mEq/L 1.86-1.94 Yes
Chloride 102 mEq/L 100 mEq/L 99.9- Yes 104.0 Calcium 6.8 mg/dl 6.8
mg/dl 6.6-6.94 Yes Magne- 1.2 mEq/L 1.2 mEq/L 0.000.00 Yes sium
Aluminum 0.099 mg/L 0.100 mg/L 0.097- Yes 0.101 Copper <0.002
mg/L <0.002 mg/L 0.00 Yes Selenium <0.050 mg/L <0.050 mg/L
0.00 Yes Zinc 0.006 mg/L 0.006 mg/L 0.00 Yes Chromium <0.005
mg/L <0.005 mg/L 0.00 Yes Lead <0.001 mg/L <0.001 mg/L
0.00 Yes Arsenic <0.002 mg/L <0.002 mg/L 0.00 Yes Mercury
<0.0002 mg/L <0.0002 mg/L 0.00 Yes Cadmium <0.001 mg/L
<0.001 mg/L 0.00 Yes Fluoride <0.10 mg/L <0.10 mg/L 0.00
Yes Nitrate <0.2 mg/L <0.2 mg/L 0.00 Yes Sulfate 1.0 mg/L 1.0
mg/L 0.00 Yes Silver <0.003 mg/L <0.003 mg/L 0.00 Yes Barium
0.002 mg/L 0.002 mg/L 0.00 Yes
______________________________________ **concentration variance of
2%.
Example 10
Changes to solution in terms of conductivity/resistivity and
extrapolate to parts per million (or parts per billion) amounts of
material contributed by a filter as described in Example 8 into the
filtrate, using ultrapure de-ionized water as a filter throughput
solution.
One-at-a-time, two filters were installed in a pressurized DI water
line with a resistivity monitoring cell before and after the
filter. The control valve was slowly opened and 1,000 ml/min flow
of DI water through the filter was obtained and maintained. The
inlet and outlet resistivity cell values were read and recorded at
least every five minutes for a 30 minute period. The values were
averaged for the two filters to arrive at a single inlet DI water
resistivity value and a single outlet water resistivity value. The
resistivity values were converted to ppm (or ppb) and the inlet
value was subtracted from the outlet value to determine approximate
ionic content added to DI water from the filter. Resistivity values
were averaged over the 30 minute period and between the two filters
used. Filtrate conductivity=0.169 .mu.S/cm (or 0.37 ppm). This was
an increase from the inlet DI water conductivity of 0.066 .mu.S/cm
(or 0.145 ppm). Therefore, approximately 0.224 ppm (or 224 ppb) of
unknown ionic shedding or release of dissolved solids can be
attributed to the filter.
TABLE V ______________________________________ Change in Throughput
Solution Resistivity Due to Filters T = 0 Minutes T = 30 Minutes
Average Inlet Water Filtrate Filtrate Filtrate Resistivity,
Resistivity, Resistivity, Resistivity, Filter # Megohm-cm Megohm-cm
Megohm-cm Megohm-cm ______________________________________ 1.00
15.38 7.00 5.70 6.25 2.00 14.55 5.63 5.30 5.48 AVG 15.10 6.32 5.50
5.90 ______________________________________
Example 11
The filter inlet and outlet pressures (mmHg) were observed in water
and final bicarbonate-based dialysate for a filter as described in
Example 8. The transmembrane pressure drop was also examined as it
related to the filter's effect upon the dialysate stream pressures
and flow rates. A filter as described in Example 8 was installed on
a Travenol 450 SPS dialysis machine between dialyzer-in and
dialyzer-out dialysate lines. The sample port Tees, with 3-way
stopcocks attached were installed in the upstream and downstream
lines. Tubing was attached between the stopcocks and the
Digi-dyne.sup.- pressure monitor transducers (one for filter inlet
pressure and one for filter outlet pressure). The stopcocks were
opened to the monitoring tubing and turned on the pressure
monitors.
RO water throughput at a flow at 600 ml/min was initiated.
Transmembrane pressure drop was observed across the filter. The
nature of the filter and whether or not the filter functioned as a
flow restrictor was detected by measuring flow in the drain line
with a graduated cylinder over a one minute period.
With the dialysis machine still running at 600 ml/min and monitor
lines still open, dialysate throughput flow was initiated by
connecting concentrate uptake lines to sterile, non-pyrogenic
liquid bicarbonate and acid electrolyte concentrate containers. The
acid concentrate used .[.were.]. .Iadd.was .Iaddend.Renal Systems
SB-1075 and the bicarbonate concentrate used was BC-1-L.
Concentrates were diluted internally by the Travenol 450 SPS using
RO water meeting the AAMI standards for water used to make
dialysate.
The dialysate conductivity was allowed to stabilize as indicated by
a NEO-1 Dialysate Meter reading of .Iadd.the .Iaddend.filter inlet
stream. We also waited until the machine issued no
dialysate-related alarm conditions.
A throughput of 37.degree. C., properly proportioned,
bicarbonate-based, final dialysate was continued at 600 ml/min for
30 minutes. The transmembrane pressure drop across the filter was
observed during dialysate throughput. Again, it was determined if
the filter functioned as a flow restrictor by measuring flow in the
drain line with a graduated cylinder over a one minute period.
As shown in the FIG. 7, the filter displayed a one-time variance in
pressure drop that is corrected the first time each filter contacts
final dialysate solution. The initial transmembrane pressure drop
at 600 ml/min in RO water is about 260-340 mmHg initially. Within a
few minutes, once the membrane is thoroughly "wetted", the TMP drop
falls to about 200 mmHg and is stable. When contact with ion-rich
dialysate occurs, the figure shows how we cycled back and forth
between RO water and dialysate three times to illustrate the
permanence of the change in pressure drop once dialysate contact
occurs. At no time did the filter function as an actual in-line
flow restrictor.
Example 12
Several different hollow fiber membrane devices were installed,
one-at-a-time on a dialysis machine, under identical operating
conditions, and the differences in transmembrane pressure drop in
water and dialysate were determined for each device.
A filter as described in Example 8 was installed on a fully warmed
up Travenol 450 SPS dialysis machine (line
temperature=37.degree..+-.2.degree. C.) between dialyzer-in and
dialyzer-out dialysate lines. Sample port Tees, with 3-way
stopcocks attached, were installed in the upstream and downstream
lines. Tubing was attached between the stopcocks and Digi-dyne.RTM.
pressure monitor transducers (one for filter inlet pressure and one
for filter outlet pressure). The stopcocks were opened to the
monitoring tubing and the pressure monitors were turned on.
RO water throughput flow at 600 ml/min was initated and maintained
for at least five minutes to allow conditions to stabilize. The
flow rate was verified by measuring flow in the drain line with a
graduated cylinder over a one minute period. The inlet and outlet
pressures were recorded and the transmembrane pressure drop across
the filter was calculated.
With the dialysis machine still running at 600 ml/min and monitor
lines still open, dialysate throughput flow was initiated by
connecting concentrate uptake lines to sterile, non-pyrogenic
liquid bicarbonate and acid electrolyte concentrate containers. The
acid concentrate used was Renal Systems.RTM. SB-1075 and the
bicarbonate concentrate used was BC-1-L. Concentrates were diluted
internally by the Travenol 450 SPS using RO water exceeding the
AAMI standards for water used to make dialysate.
The time count began at "0" when concentrate .[.is.]. .Iadd.was
.Iaddend.hooked up to the dialysis machine. The inlet and outlet
pressures were recorded and the transmembrane pressure drop across
the filter was recorded every minute up to 10 minutes. The
concentrate containers were then disconnected. After five minutes,
a final measurement of inlet and outlet pressures was recorded and
a final transmembrane pressure drop was calculated.
Steps one through five were repeated for a dialyzer using the same
membrane as the RenaGuard.TM. Dialysate Filter (polyimide), a
Minntech Primus.RTM.1350 dialyzer (polysulfone), and a Fresenius
F60 dialyzer (polysulfone).
Both the RenaGuard.TM. Dialysate Filter and a dialyzer made with
polyimide fibers had lower pressure drops than both of the Minntech
and Fresenius polysulfone units. The results are set forth in FIG.
8. Polyimide fiber units had a lower pressure drop in dialysate
than in RO water. The polysulfone units, on the other hand, had a
higher pressure drop in dialysate.
Dialysate TMP drop measurements were done for the Fresenius F80
dialyzer and Fresenius DIASAFE hemodiafiltration unit for
comparison to the RenaGuard.TM. Dialysate Filter in the dominant
fluid environment, i.e., final dialysate.
The RenaGuard.TM. Dialysate Filter had a lower pressure drop in
dialysate than either the Fresenius F80 dialyzer or the Fresenius
DIASAFE hemodiafiltration filter. The results are set forth in FIG.
9.
Example 13
A "mock dialysis treatment" was set up with the dialysate filter as
described in Example 8 installed immediately pre-dialyzer on a
ultrafiltration-controlled (UFC) dialysis machine. The purpose of
the mock dialysis treatment was to verify that the "treatment"
could proceed from start to finish without alarm conditions caused
by the filter, and, that the fluid removal goal for the "treatment"
was within 2% of programmed goal.
A filter as described in Example 8 was installed on a Fresenius
A2008H UFC dialysis machine between dialyzer-in and dialyzer-out
dialysate lines. This configuration is set forth in FIG. 1.
Setup conditions included priming a Fresenius F60 dialyzer with
normal saline, installing it on the A2008H machine utilizing the
blood pump, pressure monitor lines, and a bucket containing saline
to simulate the "patient". Blood "in" and blood "out" lines had
Hoffman clamps attached to control the occlusion of the blood
lines. Occlusions were set so that at a blood pump speed of 300
ml/min, the "arterial" and "venous" pressures were normalized.
Concentrates were hooked up to the machine and it was allowed to
come into appropriate conductivity and temperature. At the time of
"treatment", the temperature=36.degree. C., the dialysate flow
rate=500 ml/min, and the dialysate conductivity was 14.1 mS/cm.
The dialysis machine was programmed to remove 1000 ml of fluid from
the "patient" in a 30 minute "treatment" time. This is the
equivalent of an ultrafiltration rate of 2.0 kg/hr.
Pressures were monitored before the filter, between the filter and
the
dialyzer dialysate inlet, and after the dialyzer during the
"treatment".
During the first "mock dialysis treatment," 1,000 ml was programmed
into the A2008H to be removed from the "patient", the A2008H
reported that 1,000 ml had been removed, and by collecting effluent
from the ultrafiltration pump it was determined that 1,015 ml had
actually been removed. This is an error of only 1.5%.
A second mock dialysis treatment was conducted with the filter
inlet compartment about half full of air to determine if the
reduced functional surface area would cause any "treatment" related
problems. The same filter was used as in the first "treatment". The
parameters were identical to those used in the first
"treatment".
During the second "mock dialysis treatment" with an air-filled
filter in-line, 1,000 ml was programmed into the A2008H to be
removed from the "patient", the A2008H reported that 1,000 ml had
been removed, and by collecting effluent from the ultrafiltration
pump it was determined that 1,010 ml had actually been removed.
This is an error of only 1.0%.
Example 14
In the following example, filters as described in Example 8 were
used with a dialysate throughput of 20,000 liters.
Two dialysate filters were installed on a test bench containing a
50-liter container of correctly proportioned bicarbonate-based
dialysate. Using Tygon tubing segments and appropriate connectors,
each filter was connected to a roller pump that drew dialysate out
of the container, pushed it through the filter, and returned
dialysate filtrate back into the container at a constant flow rate
of 800 ml/min.
This test simulated the use of greater than one month's worth of
poor-quality dialysate at a higher than usual throughput flow rate.
Dialysate flow rates can vary from 500-1,000 ml/min, however,
typically they do not exceed 600 ml/min. Bacterial load in the
50-liter container varied from 10 cfu/ml at the start of the study
to 300 cfu/ml at the end of the study.
Post-filter samples for each filter and the 50-liter container were
sampled periodically during the test and after 18 days of dialysate
recirculation and throughput. Collection of dialysate container
samples was accomplished by using a sterile 25 ml pipette to
transfer at least 100 ml of dialysate from the container into a
sterile collection bottle. Collection of post-filter samples was
accomplished by using a "clean catch" method. The downstream tubing
connector was removed from the filter and dialysate was allowed to
run out of the outlet port for about 5 seconds. A sterile
collection bottle was placed under the stream and at least 100 ml
of solution was collected.
Collection bottle contents were filtered through a 0.2 .[.um.].
.Iadd..mu.m .Iaddend.Nalgene disposable filter. Sterile forceps
were used to transfer the membrane portion .[.df.]. .Iadd.of
.Iaddend.the filter onto Tryptic soy agar (TSA) for determination
of cfu/ml. TSA Plates were incubated at 37.degree. C. for 48
hours.
At the 20,000 liters throughput level, 48 hour plates showed "no
growth" for the outlet samples of both filters. Shortly after the
start of the study, the dialysate container sample showed about 300
cfu/ml of bacteria within the dialysate solution entering the
dialysate filter inlets.
Example 15
A single filter as described in Example 8 was removed from its
package and installed on a Travenol 450 SPS dialysis machine,
between the lines normally used as dialysate-inflow and
dialysate-outflow for the dialysate compartment on a hemodialyzer
during dialysis. Properly proportioned bicarbonate-based 37.degree.
C. dialysate throughput was initiated and maintained at 600
ml/min.
Prior to installation of the dialysate filter, the Travenol machine
had been treated with 250 ml of Renalin.RTM. Concentrate diluted
within the dialysis machine 1:8 in RO water and allowed to dwell
within the machine for 30 minutes. After this time, the machine was
allowed to rinse until peracetic acid test strips indicated <1
ppm in the drain line. Peroxide levels from the Renalin.RTM. were
also verified <1 ppm in filter outlet samples as detected by
using a Spectrophotometer.
A bacterial suspension of Escherichia coli, grown on TSA and
diluted with 25 ml of bicarbonate dialysate, was added to the
bicarb concentrate jug to "spike" the final dialysate entering the
dialysate filter. The Travenol machine was hooked up to this
"contaminated" bicarbonate concentrate and allowed to proportion
per normal functioning. This resulted in a bacterial challenge
level of at least 1.6.times.10.sup.7 cfu/ml.
Samples of at least 100 ml were collected from pre- and post-filter
sample ports using "clean catch" technique at T=0, 5, 30, and 60
minutes. Samples were filtered through a 0.2 .mu.m Nalgene
disposable filter. Sterile forceps were used to transfer the
membrane portion of the filter onto Tryptic soy agar (TSA) for
determination of cfu/ml. TSA Plates were incubated at 37.degree. C.
for 48 hours.
Environmental and media controls were negative. Positive control
was positive for growth. All culture results are reported in cfu/ml
after 48 hours incubation at 37.degree. C. Note in the Table below
that all filtrate samples were negative.
TABLE VI ______________________________________ Sample cfu/ml
______________________________________ T = 0 Pre-filter 1 T = 0
Post-filter 0 T = 0 Bicarb jug 1.8 .times. 10.sup.7 T = 5
Pre-filter 1.6 .times. 10.sup.7 T = 5 Post-filter 0 T = 30
Pre-filter 1.9 .times. 10.sup.7 T = 30 Post-filter 0 T = 60
Pre-filter 1.9 .times. 10.sup.7 T = 60 Post-filter 0
______________________________________
Example 16
Two dialysate filters as described in Example 8 were installed on
separate Travenol 450 SPS dialysis machines and left attached
between the dialysate-inflow and dialysate-outflow lines. Each
filter was exposed to over 600 liters of throughput, 500 liters of
which were properly proportioned final bicarbonate-based dialysate,
the remainder being RO water. The throughput flow rate was 600
ml/min.
One filter was challenged with Escherichia coli bacteria in
dialysate after two days; the other filter was similarly challenged
after three days of installation. As in Example 15, a bacterial
suspension of Escherichia coli; grown on TSA and diluted with 25 ml
of bicarbonate dialysate, was added to the bicarb concentrate jug
to "spike" the final dialysate entering the dialysate filter. The
Travenol machine was hooked up to this "contaminated" bicarbonate
concentrate and allowed to proportion per normal functioning. This
resulted in a bacterial challenge level of at least
3.6.times.10.sup.4 cfu/ml.
Prior to initiating the bacterial challenge, each Travenol machine
had been treated with 250 ml of Renalin.RTM. Concentrate diluted
within the dialysis machine 1:8 in RO water and allowed to dwell
within the machine for 30 minutes. After this time, the machine was
allowed to rinse until peracetic acid test strips indicated <1
ppm in the drain line. Peroxide levels from the Renalin.RTM. were
also verified <1 ppm in filter outlet samples as detected by
using a Spectrophotometer.
Once the contaminated bicarb jug was hooked up to the Travenol
machine, samples of at least 100 ml were collected from pre- and
post-filter sample ports using "clean catch" technique at T=0, 5,
30, and 60 minutes. Samples were filtered through a 0.2 .[.um.].
.Iadd..mu.m .Iaddend.Nalgene disposable filter. Sterile forceps
were used to transfer the membrane portion of the filter onto
Tryptic soy agar (TSA) for determination of cfu/ml. TSA Plates were
incubated at 37.degree. C. for 48 hours.
Environmental and media controls were negative. Positive control
was positive for growth. All culture results are reported in cfu/ml
after 48 hours incubation at 37.degree. C.
TABLE VII ______________________________________ Filter #1, After 2
days Sample cfu/ml ______________________________________ T = 0
Pre-filter 147 T = 0 Post-filter 2 T = 0 Bicarb jug 1.5 .times.
10.sup.6 T = 5 Pre-filter 2.5 .times. 10.sup.5 T = 5 Post-filter 0
T = 30 Pre-filter 2.1 .times. 10.sup.5 T = 30 Post-filter 0 T = 60
Pre-filter 2.2 .times. 10.sup.5 T = 60 Post-filter 1
______________________________________
TABLE VIII ______________________________________ Filter #2, After
3 days Sample cfu/ml ______________________________________ T = 0
Pre-filter 319 T = 0 Post-filter 0 T = 0 Bicarb jug 4.7 .times.
10.sup.5 T = 5 Pre-filter 3.6 .times. 10.sup.4 T = 5 Post-filter 33
T = 30 Pre-filter 4.7 .times. 10.sup.4 T = 30 Post-filter 1 T = 60
Pre-filter 3.7 .times. 10.sup.4 T = 60 Post-filter 1
______________________________________
Example 17
Eight (8) ETO'd dialysate filters as described in Example 8, were
challenged to verify retention of Pseudomonas aeruginosa endotoxin
in final dialysate at flowrates of 500-1,000 ml/min.
Eight filters were installed in the test setup for one-at-a-time
evaluation. For seven of these filters, this setup consisted of
inlet and outlet tubing with Hansen-style connectors for each
filter's inlet and outlet ports, a roller pump, an inlet and outlet
sampling port installed pre- and post-filter and clean pyrogen-free
21/2 gallon polyethylene jugs (containers for the rinsing and
challenging solutions). One filter, however, was installed on a
Travenol 450 SPS dialysis machine, between the dialyzer inlet and
dialyzer outlet lines-connected in the same way a dialyzer's
dialysate ports would be during a hemodialysis treatment.
Filters were "rinsed" with final bicarbonate-based dialysate
solution at 500 ml/min for 30 minutes before being "challenged"
with contaminated dialysate (containing the Pseudomonas aeruginosa
endotoxin).
Frozen, dried lipopolysaccharide (LPS, endotoxin), isolated from
Pseudomonas aeruginosa by phenol extraction was reconstituted per
the manufacturer's instructions and added to the final
bicarbonate-based dialysate solution immediately prior to
initiating the test. The 21/2 gallon container was vigorously
shaken and then placed on a magnetic stirring platform, with a
stirring bar in the bottom, to help keep the solution mixed.
Prior to starting the test, the pre- and post-filter ports, with no
filter in-line, were sampled to verify pyrogen-free status. Ports
were checked again, with filter in-line, before administering the
endotoxin challenge to verify that the filter was clean and that
the test setup did not become contaminated during the installation
of the filter.
Once the flow of contaminated dialysate was initiated through the
filter, samples were collected from the pre- and post-filter sample
ports at T=1, 3, and 5 minutes.
The gel-clot method of Limulus Amebocyte Lysate endotoxin assaying
was used to analyze all samples for presence, absence, or
quantification of endotoxin. Additional test conditions included
the following:
a. One filter was challenged in both DI water and dialysate. This
filter received two back-to-back endotoxin challenge tests.
b. Two filters were challenged with LPS that had been sonicated in
addition to vortexing.
c. One filter was challenged with a throughput flowrate=800 ml/min
instead of 500 ml/min.
d. One filter was challenged with a throughput flowrate=1,000
ml/min in addition to the 500 ml/min rate. This filter also
received two back-to-back endotoxin challenge tests.
e. One filter had been "pre-treated" by installing it as a
pre-filter for the Renatron.RTM. artificial kidney reprocessing
machine. It was exposed to RO water throughput conditions of up to
6.2 liters/min (6,200 ml/min) during ten (10) Renatron.RTM.
processing cycles.
f. Again, one filter was installed on a dialysis machine as
described above and exposed to throughput flowrates of 600 ml/min.
This dialysis machine picked up the endotoxin contamination from
the water inlet to the machine, instead of from contaminated
dialysate. Frozen, dried Pseudomonas aeruginosa LPS, was
reconstituted per the manufacturer's instructions and added to the
water supply for the dialysis machine (a 50-liter polyethylene
container). To provide adequate pressure for dialysis machine
operation, a roller pump "pushed" the contaminated water stream
into the dialysis machine.
Filters received endotoxin challenges varying in potency from 4.8
EU/ml up to 60 EU/ml of Pseudomonas aeruginosa endotoxin at final
bicarbonate-based dialysate throughput flowrates of 500 ml/min, 800
ml/min, or 1,000 ml/min. Each of the filters retained all
endotoxin. No detectable endotoxin is reported as <0.06 EU/ml,
the limit of sensitivity for the Lysate used in the assay.
TABLE IX ______________________________________ Pseudomonas
aeruginosa Dialysate Endotoxin Challenge Endotoxin Challenge
Endotoxin Filtrate Filter Level, Level, EU/ml Treatment # EU/ml 1
MIN 3 MIN 5 MIN conditions ______________________________________ 1
6 <0.06 <0.06 <0.06 Also DI water, 48 EU/ml in, <0.06
EU/ml in all outlet samples 2 6 <0.06 <0.06 <0.06 -- 3 12
<0.06 <0.06 <0.06 Pseudomonas LPS sonicated & vortexed
prior to use 4 60 <0.06 <0.06 <0.06 Pseudomonas LPS
sonicated & vortexed prior to use 5 12 <0.06 <0.06
<0.06 800 ml/min throughput flowrate 6 24 <0.06 <0.06
<0.06 Run on dialysis machine, 600 ml/min LPS introduced into
water inlet 7 4.8 <0.06 <0.06 <0.06 Pre-treated with 10
Renatron .RTM. cycles 8 6 <0.06 <0.06 <0.06 Also 1,000
ml/min throughput flowrate, 12 EU/ml inlet, <0.06 EU/ml outlets
______________________________________
Example 18
Six (6) ETO'd filters as described in Example 8 were challenged
with endotoxin in RO water at flowrates of 2,000 ml/min and verify
endotoxin retention.
Six filters were individually removed from the Tyvek bag used
during the ETO sterilization process and installed in the test
setup for one-at-a-time evaluation. RO water was used as the
challenge solution due to the difficulty presented in producing
large volumes of clean dialysate to support the 2 liters per minute
flow rate used in this test.
The test setup used in Example 17 was also used for this test
series. The most noteworthy differences between Example 17 and this
example include the following:
a. RO water was used instead of final bicarbonate-based
dialysate.
b. Throughput flowrate=2,000 ml/min instead of the 500-1,000 ml/min
used in Example 17.
c. The first two filters were challenged using endotoxin derived
from Escherichia coli. The last four were challenged with
Pseudomonas aeruginosa LPS.
d. The last five filters tested had LPS delivered into the
dialysate by using a metered syringe pump with a glass syringe. The
concentrated, reconstituted LPS was drawn up into the syringe and a
line attached to the filter inlet tubing. The syringe pump injected
endotoxin at a controlled rate from the syringe directly into the
filter inlet stream.
Prior to starting the test, pre- and post-filter ports, with no
filter in-line, were sampled to verify pyrogen-free status of the
test setup. Ports were checked again, with filter in-line, before
administering the endotoxin challenge to verify that the filter was
clean and that the test setup did not become contaminated during
the installation of the filter.
Samples were collected from filter inlet and outlet sample ports at
T=1 and T=4 minutes after LPS administration was initiated. Once
the 4 minute samples were collected, with the syringe pump still
"on" the filter was removed and filter inlet and outlet ports were
sampled again to verify that endotoxin was present in both ports,
showing that reduced endotoxin concentrations were not caused by
some artifact in the test setup.
Again, the gel-clot method of Limulus Amebocyte Lysate endotoxin
assaying was used to analyze all samples for presence, absence, or
quantification of endotoxin. To simplify the testing process, a
"Pass/Fail Limits Test" was used. Rather than perform an extensive
dilution series to determine the exact concentration of endotoxin
present in the contaminated dialysate, a single appropriately
diluted sample was used, which if positive, indicated the minimum
level of endotoxin present, e.g., .gtoreq.15 EU/ml.
Filters received endotoxin challenges varying in potency from
.gtoreq.15 EU/ml up to 48 EU/ml; of either Escherichia coli or
Pseudomonas aeruginosa endotoxin at RO water throughput flowrates
of 2,000 ml/min. Each filter retained all endotoxin contained
within the challenge solution. No detectable endotoxin is reported
as <0.06 EU/ml, the limit of sensitivity for the Lysate used in
the assay. (See Table below for details.)
TABLE X ______________________________________ Syringe Pump
Endotoxin Challenge at 2,000 ml/min Endotoxin Endotoxin Challenge
Filtrate Filter Level, Level, EU/ml # EU/ml 1 MIN 4 MIN Treatment
conditions ______________________________________ 1 48 <0.06
<0.06 E. Coli LPS, contaminated RO water in 21/2 gallon jug 2 24
<0.06 <0.06 E. Coli LPS, Syringe pump administration 3
.gtoreq.15 <0.06 <0.06 P. aeruginosa LPS, Syringe pump
administration 4 .gtoreq.15 <0.06 <0.06 P. aeruginosa LPS,
Syringe pump administration 5 .gtoreq.15 <0.06 <0.06 P.
aeruginosa LPS, Syringe pump administratoin 6 .gtoreq.15 <0.06
<0.06 P. aeruginosa LPS, Syringe pump administration
______________________________________
Example 19
To evaluate reusability of the filters of the present invention as
described in Example 8, four (4) filters that demonstrated
"shedding" of LAL-reactive material were treated with Renalin.RTM.
Concentrate to recover their endotoxin retention capability.
To produce this condition in which filters release or "shed"
LAL-reactive material, filters were run 24 hours/day on a
recirculation setup with contaminated dialysate. Shedding only
occurs in filters that have not been periodically re-sterilized
during use (every 24-48 hours).
This "recirculation" setup included a 50-liter container of final
bicarbonate-based dialysate, a roller pump, and connecting tubing
with Hansen-style connectors for attachment to filter .[.in-lets.].
.Iadd.inlets .Iaddend.and outlets. The roller pump moved dialysate
up to the pump, through the filters, and returned the dialysate
filtrate back into the 50-liter container. This setup provided
throughput of 800 ml/min, 24 hours/day for each filter. The
dialysate was deliberately not disinfected so that levels of
bacteria in the tank would rise over time.
Before the re-evaluation of endotoxin retention was conducted, all
four units were pre-treated on the "recirculation" setup until they
began to "shed" LAL-reactive material into throughput solutions.
"Shedding" was verified using gel-clot LAL assays of filtrate
samples.
We had observed, that at a point between 10,000 liters and 20,000
liters total dialysate throughput, the filters began "shedding" of
LAL-reactive material into the filtrate. Concurrently, the pressure
drop across the filters had doubled. That is, they showed less
permeability to throughput fluids, and no longer served to
depyrogenate the fluids flowing through them. When pyrogen-free RO
water was input to the filter the fluid became LAL-reactive.
To evaluate the "recoverability" of these "saturated" filters, a
method was devised to disinfect and clear the membrane of this
LAL-reactive material. It was hypothesized that this material
consisted of accumulated bacteria and endotoxin, precipitated salts
and carbonates, and by-products of bacterial metabolism resulting
from some kind of "growthrough" phenomenon. Note that the filters
had not been disinfected or re-sterilized during the entire time of
their installation in the recirculating setup.
The membrane disinfection and clearing procedure consisted of the
following steps:
a. Removing the filter from the recirculating setup.
b. Installing it in reverse configuration (to "blow off" the
material impacted on the membrane surface) on a
Travenol 450 SPS dialysis machine, in between the dialysate in-flow
and out-flow lines.
c. Running RO water through the filter at 600 ml/min during a
Renalin.RTM. Concentrate chemical treatment on the dialysis
machine.
1) Allowing the dialysis machine to draw up 250 ml of Renalin.RTM.
Concentrate through the acid concentrate uptake line (resulting in
a 1:8 dilution of Renalin.RTM. Concentrate in the filter and
machine dialysate lines).
2) Turning off the dialysis machine and allowing the diluted
Renalin.RTM. Concentrate to dwell inside the filter for 30
minutes.
3) Turning on the dialysis machine and "rinsing" the filter with RO
water until <1 ppm of Renalin.RTM. was detected. This took about
20 minutes to accomplish.
d. Re-orienting the filter to normal flow direction and installing
it on the endotoxin challenge test bench.
All four filters ran on the recirculating test setup until they
began to "shed" LAL-reactive material. They were then given the
Renalin.RTM. membrane clearing and disinfecting treatment described
above and installed on the endotoxin challenge test bench in
preparation for the post-treatment LPS retention test.
This endotoxin test setup consisted of a roller pump, inlet and
outlet tubing and Hansen-style connectors, pre- and post-filter
sampling ports, and 21/2 gallon polyethylene containers for holding
the challenge solutions. All tests used DI water throughput at a
flowrate=500 ml/min.
Again, the gel-clot method of Limulus Amebocyte Lysate endotoxin
assaying was used to analyze all samples for presence, absence, or
quantification of endotoxin.
Prior to starting the test, the pre- and post-filter ports, with no
filter in-line, were sampled to verify non-pyrogenic status. Ports
were checked again, with filter in-line, before administering the
endotoxin challenge to verify that the filter was clean and that
the test setup did not become contaminated during the installation
of the filter.
Frozen, dried lipopolysaccharide (LPS, endotoxin), isolated from
Escherichia coli by phenol extraction, was reconstituted per the
manufacturer's instructions and added to a 21/2 gallon container of
pyrogen-free RO water immediately prior to initiating the test. The
21/2 gallon container was vigorously shaken and then placed on a
magnetic stirring platform, with a stirring bar in the bottom, to
help keep the solution mixed.
Once the LPS contamination was initiated, samples were collected
from filter inlet and outlet sample ports at T=1, 3, and 5
minutes.
Filters were exposed to recirculating dialysate throughput
flowrates of 800 ml/min, 24 hours/day until the transmembrane
pressure drop had doubled. Within this highly exaggerated test
condition, the filters began to "shed" LAL-reactive material.
Filters were then subjected to a Renalin.RTM. membrane clearing and
disinfecting procedure.
Filters then received follow-up endotoxin challenges varying in
potency from .gtoreq.7.7 EU/ml up to 30.7 EU/ml of Escherichia coli
endotoxin at RO water throughput flowrates of 500 ml/min. Each
filter retained all endotoxin contained within the challenge
solution. No detectable endotoxin was reported as <0.06 EU/ml,
the limit of sensitivity for the Lysate used in the assay. (See
Table below for details.)
TABLE XI ______________________________________ Recovery of
Endotoxin Retention After Renalin .RTM. Exposure "Shedding" LAL-
reactive Endotoxin Material Challenge before Level, Endotoxin
Filtrate Renalin .RTM. EU/Ml Level, EU/ml Filter Treatment
Treatment ? (After 1 3 5 # conditions (Y/N) Renalin .RTM.) MIN MIN
MIN ______________________________________ 1 20,000 liters Yes,
15.4 <0.06 <0.06 <0.06 recirculated >0.06 EU/Ml
dialysate, then Renalin .RTM. treated 2 20,000 liters Yes, 15.4
<0.06 <0.06 <0.06 recirculated >0.06 EU/Ml dialysate,
then Renalin .RTM. treated 3 20,000 liters Yes, 7.7 <0.06
<0.06 <0.06 recirculated >0.06 EU/Ml dialysate, then
Renalin .RTM.
treated 4 20,000 liters Yes, 30.7 <0.06 <0.06 <0.06
recirculated >0.06 EU/Ml dialysate, then Renalin .RTM. treated
______________________________________
Example 20
The outlet header cap of a filter as described in Example 8 was
contaminated with 0.1 ml of a 10.sup.10 cfu/ml suspension Bacillus
subtilis spores, 25 ml of Renalin.RTM. Cold Sterilant Concentrate
was then injected into the filter for a 12 hour dwell period and
viability of the spores was checked.
A dialysate filter, representative of final sterilized product, was
installed on a Travenol 450 SPS dialysis machine between the
dialyzer-in and dialyzer-out dialysate lines. Flow was initiated
through the filter at 600 ml/min and the machine was connected to
bicarbonate and acid electrolyte solutions. The machine was allowed
to proportion final dialysate until 37.degree. C. temperature and
13.8 mS/cm solution conductivity was obtained (normal final
dialysate parameters).
The dialysis machine was turned off and 25 ml of Renalin.RTM. Cold
Sterilant Concentrate was injected into the Luer port provided on
the filter. The outlet header coupler was then disconnected and 0.1
ml of a 10.sup.10 cfu/ml Bacillus subtilis bacterial endospore
suspension was pipetted into the header cap.
The filter was left installed in the dialysate lines on the
dialysis machine, with the Renalin.RTM. dwelling for about 16
hours.
After the dwell period, the filter unit was removed from the
dialysis machine and the fluid it contained was drained into a
sterile collection bottle. It was then re-attached to the dialysis
machine and the machine turned on to flush another 100 ml out
through the unit. The end volume in the collection bottle was about
200 ml.
This 200 ml of effluent solution was aseptically filtered through a
0.2 .mu.m membrane filter. It was then rinsed with 90 ml of 1%
peptone/1% sodium thiosulfate solution to neutralize the
Renalin.RTM., followed by 100 ml sterile DI water.
The effectiveness of this 90 ml 1% peptone/1% sodium thiosulfate
neutralizing "rinse" procedure was verified. By contaminating the
100 ml sterile DI water used as a rinse (above) with Bacillus
subtilis spores, plating the 0.2 .mu.m filter on TSA, and
incubating at 37.degree. C. for 24 hours, we were able to show
bacterial growth. This indicates effective neutralization of the
Renalin.RTM. used in the test.
After 48 hours incubation at 37.degree. C., one colony grew on the
0.2 .mu.m membrane filter. This colony had a similar morphology to
the inoculated organism (Bacillus subtilis). To confirm the
presence of the inoculated organism, a Gram stain was done on the
colony. The results of the Gram stain showed gram positive cocci
instead of the Gram negative bacilli sporeformer. This suggests
that the single colony was the result of some type of contamination
during either preparation or collection.
Example 21
To further evaluate the disinfection effectiveness of a 6 to 12
hour dwell period, a suspension containing 10.sup.10 Bacillus
subtilis bacterial endospores were injected into the fluid inlet
stream of four filters as described in Example 8, driving the
spores against the filter membrane. Inject 10-25 ml of Renalin.RTM.
Cold Sterilant Concentrate into each filter, and check viability of
spores after six to twelve hours.
First a test was conducted to demonstrate the recoverability of
Bacillus subtilis spores impacted upon the dialysate filter
membrane. An ETO-sterilized dialysate filter was installed on a
Travenol 450 SPS dialysis machine between the dialyzer-in and
dialyzer-out dialysate lines. RO water flow was initiated through
the filter at 600 ml/min. One ml of about 10.sup.10 Bacillus
subtilis spores .[.were.]. .Iadd.was .Iaddend.injected into the
filter's inlet stream. The dialysis machine was allowed to run for
about 5 more minutes. Then, by reversing the filter's installation
configuration we were able to "blow off" the spores embedded or
impacted upon the membrane. Recovery was estimated to be nearly
100%.
Then, each of the four filters to be used in the sporicidal
Renalin.RTM. treatment test was installed one-at-a-time on a
Travenol 450 SPS dialysis machine between the dialyzer-in and
dialyzer-out dialysate lines. RO water flow was initiated through
each filter at 600 ml/min. One ml containing 10.sup.10 spores was
injected into the filter's inlet stream and the machine was allowed
to run for another 5 minutes to drive the spores against the
membrane. The machine was turned off and 10 ml of Renalin.RTM.
Concentrate was injected into the Luer port on each filter. The
filters remained installed on the dialysis machine for a minimum of
six hours.
This 10 ml of Renalin.RTM. Cold Sterilant Concentrate, injected
into the 85 ml fluid volume of the filter, yields an effective
Renalin.RTM. concentration of .gtoreq.1% (about 2.8% hydrogen
peroxide within the filter).
After the dwell period, the flow through each filter was reversed
by disconnecting the two dialysate lines and reconnecting the
"upstream" line to the "downstream" port. The dialysis machine was
turned on and throughput flow initiated at 600 ml/min for about 30
seconds. Filtrate was collected (about 300 ml) in a sterile
collection bottle.
Filtrate was then passed through a sterile 0.2 .mu.m Nalgene
analytical filter, followed by at least 90 ml of the "neutralizing
rinse" used in the previous test. The neutralizing rinse was then
followed by at least 100 ml of sterile DI water.
The analytical membrane filter was then moved with a sterile
forceps onto a TSA plate and allowed to incubate for at least 48
hours at 37.degree. C. If any growth was present, a Gram stain was
done to help determine if the colony was the same as the
inoculating .[.organis.]. .Iadd.organism .Iaddend.(Bacillus
Subtilis).
After 48-72 hours incubation at 37.degree. C., filter#1's test
solution had one colony forming unit. A Gram stain was done on the
colony and it was found to be Gram positive Staphylococci, not the
inoculating organism. This is probably due to contamination during
setup or collection. Therefore, in the Table below, the result was
recorded as "no growth". The other three filters' test solutions
were all negative for any growth.
TABLE XII ______________________________________ Number Post- of
Treatment Spores Dwell Incubation Spores Filter Injected Renalin
.RTM. Time, Period, Viable, # Total Used, ml hours hours cfu/ml
______________________________________ 1 10 Billion 25 12 48 0 2 10
Billion 20 6 72 0 3 10 Billion 10 6.5 48 0 4 10 Billion 10 6 48 0
______________________________________
Example 22
The outlet header cap of a filter as described in Example 8 was
contaminated with 0.1 ml of a 10.sup.10 cfu/ml suspension Bacillus
subtilis spores, and then injected with 25 ml of Renalin.RTM. Cold
Sterilant Concentrate to check the viability of spores after twelve
(12) hours.
An ETO'd dialysate filter was installed on a Travenol 450 SPS
dialysis machine between the dialyzer-in and dialyzer-out dialysate
lines. Flow was initiated through the filter at 600 ml/min and the
machine was connected to bicarbonate and acid electrolyte
solutions. The machine was allowed to proportion final dialysate
until 37.degree. C. temperature and 13.8 mS/cm solution
conductivity was obtained (normal final dialysate parameters).
The dialysis machine was turned off and 25 ml of Renalin.RTM. Cold
Sterilant Concentrate was injected into the Luer port provided on
the filter. The outlet header coupler was then disconnected and 0.1
ml of a 10.sup.10 cfu/ml Bacillus subtilis bacterial endospore
suspension was pipetted into the header cap.
The filter was left installed in the dialysate lines on the
dialysis machine, with the Renalin.RTM. indwelling for about 12
hours.
After the dwell period, the filter unit was removed from the
dialysis machine and the fluid it contained was drained into a
sterile collection bottle. It was then re-attached to the dialysis
machine and the machine turned on to flush another 100 ml out
through the unit. The end volume in the collection bottle was about
200 ml.
This 200 ml of effluent solution was aseptically filtered through a
0.2 .mu.m membrane filter. It was then rinsed with 90 ml of 1%
peptone/1% sodium thiosulfate solution to neutralize the
Renalin.RTM., followed by 100 ml sterile DI water.
The effectiveness of this 90 ml 1% peptone/1% sodium thiosulfate
neutralizing "rinse" was verified. By contaminating the 100 ml
sterile .[.D1.]. .Iadd.DI .Iaddend.water used as a rinse (above)
with Bacillus subtilis spores, plating the 0.2 .mu.m filter on TSA,
and incubating at 37.degree. C. for 24 hours, we were able to show
bacterial growth. This indicates effective neutralization of the
Renalin.RTM. used in the test.
After 48 hours incubation at 37.degree. C., one colony grew on the
0.2 .mu.m membrane filter. This colony had a similar morphology to
the inoculated organism (Bacillus subtilis). To confirm the
presence of the inoculated organism, a Gram stain was done on the
colony. The results of the Gram stain showed gram positive cocci
instead of the Gram negative bacilli sporeformer. This suggests
that the single colony was the result of some type of contamination
during either collection or filtration and not due to resistance to
Renalin.RTM.. .[.Result.]. .Iadd.The result was .Iaddend.recorded
as "no growth".
Example 23
Four (4) prototype RenaGuard.RTM. Dialysate Filters, were injected
with a suspension containing 10.sup.10 Bacillus subtilis bacterial
endospores into each filter's fluid inlet stream, driving them
against the filter membrane. 10-25 ml of Renalin.RTM. Cold
Sterilant Concentrate was injected into the filter, and the
viability of the spores was checked after six to twelve hours.
We decided that contamination of the dialysate filter should occur
in the same manner it would clinically. That is, the bioburden
(bacteria and endotoxin) would impact on the outside of the
membrane due to the filter's normal throughput flow direction.
We first conducted a test to demonstrate the recoverability of
Bacillus subtilis spores as it impacted upon the dialysate filter
membrane. An ETO'd dialysate filter was installed on a Travenol 450
SPS dialysis machine between the dialyzer-in and dialyzer-out
dialysate lines. RO water flow was initiated through the filter at
600 ml/min. One ml of about 10.sup.10 cfu/ml Bacillus subtilis
spores .[.were.]. .Iadd.was .Iaddend.injected into the filter's
inlet stream. The dialysis machine was allowed to run for about 5
more minutes. Then, by reversing the filter's installation
configuration we were able to "blow off" the spores embedded or
impacted upon the membrane. Recovery was estimated to be nearly
100%.
Then, each of the four filters to be used in the sporicidal
Renalin.RTM. treatment test was installed one-at-a-time on a
Travenol 450 SPS dialysis machine between the dialyzer-in and
dialyzer-out dialysate lines. RO water flow was initiated through
each filter at 600 ml/min. One ml of spore suspension was injected
into the filter's inlet stream and the machine was allowed to run
for another 5 minutes to drive the spores against the membrane. The
machine was turned off and Renalin.RTM. Concentrate was injected
into the Luer port on each filter. The filters remained installed
on the dialysis machine for a minimum of six hours with
Renalin.RTM. indwelling.
After the dwell period, the flow through each filter was reversed
by disconnecting the two dialysate lines and reconnecting the
"upstream" line to the "downstream" port. The dialysis machine was
turned on and throughput flow initiated at 600 ml/min for about 30
seconds. Filtrate was collected (about 300 ml) in a sterile
collection bottle.
Filtrate was then passed through a sterile 0.2 .mu.m Nalgene
analytical filter, followed by at least 90 ml of the "neutralizing
rinse" used in the previous test. The neutralizing rinse was then
followed by at least 100 ml of sterile DI water.
The analytical membrane filter was then moved with a sterile
forceps onto a TSA plate and allowed to incubate for at least 48
hours at 37.degree. C. If any growth was present, a Gram stain was
done to help determine if the colony was the same as the
inoculating organism (Bacillus subtilis).
After 48-72 hours incubation at 37.degree. C., filter#1's test
solution had one colony growing. A Gram stain was done on the
colony and it was found to be Gram positive Staphylococci, not the
inoculating organism. .[.Result.]. .Iadd.The result was
.Iaddend.recorded as "no growth". The other three filters' test
solutions were all negative for any growth.
TABLE XIII ______________________________________ Number Post- of
Treatment Spores Dwell Incubation Spores Filter Injected Renalin
.RTM. Time, Period, Viable, # Total Used, ml hours hours cfu/ml
______________________________________ 1 100 Billion 25 12 48 0 2
100 Billion 20 6 72 0 3 100 Billion 10 6.5 48 0 4 100 Billion 10 6
48 0 ______________________________________
Example 24
A filter as described in Example 8 was challanged by exposing it to
three back-to-back 85.degree. C. heat disinfection treatments using
a Fresenius A2008H dialysis machine. The filter's endotoxin
retention capability was evaluated after exposure.
A dialysate filter was installed on a Fresenius A2008H dialysis
machine between the dialyzer-in and dialyzer-out dialysate lines.
The dialysis machine was turned on and the heat disinfection cycle
was initiated. Upon completion of this cycle, it was immediately
re-initiated two more times.
After completing all three cycles, the filter was removed from the
machine and installed on a test bench for delivering an endotoxin
challenge into the filter's inlet stream.
DI water throughput was initiated at 500 ml/min and continued for
the duration of the test. Endotoxin derived from Escherichia coli
was introduced into the filter's inlet stream at 15.4 EU/ml.
Filtrate
endotoxin levels were measured using the gel-clot method of Limulus
Amebocyte Lysate endotoxin assaying.
Filter inlet and outlet pressures were also measured and compared
to values recorded prior to heat treatments.
With 500 ml/min DI water throughput, containing a 15.4 EU/ml
Escherichia coli endotoxin level, no endotoxin was detected in
filter outlet samples at 1, 3, and 5 minutes. No detectable
endotoxin was recorded as <0.06 EU/ml, the limit of lysate
sensitivity to the presence of endotoxin. The pressure drop across
the filter did not change from values recorded prior to heat
treatment exposures.
Example 25
Filters as described in Example 8 were exposed to exaggerated
bleach contact conditions using a COBE Centry 2Rx or Travenol 450
SPS dialysis machine. The filters were re-evaluated for endotoxin
retention capability after exposure.
Three filters were exposed to full-strength bleach (5.25% sodium
hypochlorite) during 600 ml/min throughput of either RO water,
acetate dialysate, or final bicarbonate-based dialysate solutions
using a Travenol 450 SPS dialysis machine. Eight injections of
undiluted bleach, 20 cc each, were delivered into the inlet stream
of each filter at 15 minute intervals.
Two filters were exposed to approximately 30 days' worth of bleach
treatments. Both filters were given six exposures of 1,250 ml each,
with a 5 minute rinse between each exposure. The dilution level was
1:8 bleach in RO water. The dilution was accomplished by using a
COBE Centry 2Rx dialysis machine. The total bleach contact time was
2 hours and 5 minutes. The filters were installed on the dialysis
machine and the bleaching procedure followed right out of the COBE
Centry 2Rx Operator's manual. The only exception was that 7,500 ml
of bleach was used instead of the 250 ml specified in the
procedure.
All five filters were rinsed with DI water on the dialysis machine
until 0 ppm of free chlorine was detected using Hach Co. "powder
pillows" for chlorine testing and the color comparator wheel
provided with the test kit.
Filters were then installed on a test bench for administering the
endotoxin challenge, identical to the one used in Example 24.
DI water throughput was initiated at 500 ml/min and continued for
the duration of the test. Endotoxin derived from Escherichia
.[.coil.]. .Iadd.coli .Iaddend.was introduced into the filter's
inlet stream at .gtoreq.3.8 EU/ml. Filtrate endotoxin levels were
measured using the gel-clot method of Limulus Amebocyte Lysate
endotoxin assaying.
Filter inlet and outlet pressures were also measured and compared
to values recorded prior to bleach treatments.
Note that in this Example (Table), results of no detectable
endotoxin are recorded as <0.06 EU/ml, the limit of lysate
sensitivity for the test.
The first filter, exposed to bicarbonate dialysate throughput and
eight 20 cc bleach injections, was challenged with .gtoreq.7.7
EU/ml level of Escherichia coli endotoxin. No endotoxin was
detected in filter outlet samples at 5, 30, and 60 minutes.
The second filter, exposed to acetate dialysate throughput and
eight 20 cc bleach injections, was challenged with .gtoreq.7.7
EU/ml level of Escherichia coli endotoxin. No endotoxin was
detected in filter outlet samples at 5, 30, and 60 minutes.
The third filter, exposed to RO water throughput and eight 20 cc
bleach injections, was challenged with .gtoreq.7.7 EU/ml level of
Escherichia coli endotoxin. No endotoxin was detected in filter
outlet samples at 5, 30, and 60 minutes.
The fourth filter, exposed to 30 days' worth of bleach treatments,
was challenged with .gtoreq.3.8 EU/ml level of Escherichia coli
endotoxin. No endotoxin was detected in filter outlet samples at 1,
3, and 5 minutes.
The fifth filter, exposed to 30 days' worth of bleach treatments,
was challenged with .gtoreq.15.4 EU/ml level of Escherichia coli
endotoxin. No endotoxin was detected in filter outlet samples at 1,
3, and 5 minutes.
The transmembrane pressure drop across all filters decreased by
one-half after bleach exposure. This parallels the normal TMP drop
seen when other dialysate filters have been exposed to dialysate
the first time.
TABLE XIV ______________________________________ Endotoxin Filtrate
Challenge Endoroxin Filter # Pre-treat Conditions Level Level
______________________________________ 1 Eight injections of 20 cc
7.7 EU/ml <0.06 EU/ml bleach delivered during bicarbonate
throughput 2 Eight injections of 20 cc 7.7 EU/ml <0.06 EU/ml
bleach delivered during bicarbonate throughput 3 Eight injections
of 20 cc 7.7 EU/ml <0.06 EU/ml bleach delivered during RO water
throughput 4 30 Days' worth of 3.8 EU/ml <0.06 EU/ml bleach
treatments 5 30 Days' worth of 15.4 EU/ml <0.06 EU/ml bleach
treatments ______________________________________
Example 26
A filter as described in Example 8 was exposed to 30 days' worth of
Actril.RTM. disinfection treatments using a Travenol 450 SPS
dialysis machine. The filters' endotoxin retention capability after
exposure was reevaluated.
One filter was exposed to approximately 30 days' worth of
Actril.RTM. treatments. The filter was given six exposures of 1,250
ml each, with a 5 minute rinse between each exposure. The dilution
level was 1:8 Actril.RTM. in RO water. The dilution was
accomplished by using a COBE Centry 2Rx dialysis machine. The total
Actril.RTM. contact time was 2 hours and 5 minutes. The filter was
installed on the dialysis machine and the procedure followed right
out of the COBE Centry 2Rx Operator's manual. The only exceptions
were that 7,500 ml of chemical was used instead of the 250 ml
specified in the procedure, and, Actril.RTM. was used instead of
bleach.
The filter was rinsed with DI water on the dialysis machine until
<1 ppm of hydrogen peroxide was detected using Renalin.RTM.
residual test strips (for hydrogen peroxide, not peracetic
acid).
The filters was then installed on a test bench for administering
the endotoxin challenge, identical to the one used in Example
24.
DI water throughput was initiated at 500 ml/min and continued for
the duration of the test. Endotoxin derived from Escherichia coli
was introduced into the filter's inlet stream at .gtoreq.15.4
EU/ml. Filtrate endotoxin levels were measured using the gel-clot
method of Limulus Amebocyte Lysate endotoxin assaying.
Filter inlet and outlet pressures were also measured and compared
to values recorded prior to bleach treatments.
With 500 ml/min DI water throughput, containing a 15.4 EU/ml
Escherichia coli endotoxin level, no endotoxin was detected in
filter outlet samples at 1, 3, and 5 minutes. No detectable
endotoxin is recorded as <0.06 EU/ml, the limit of lysate
sensitivity to the presence of endotoxin. The pressure drop across
the filter did not change from values recorded prior to Actril.RTM.
treatment exposures.
Example 27
A filter as described in Example 8 was exposed to Renalin.RTM.
contact conditions using a Travenol 450 SPS dialysis machine. The
filter's endotoxin retention capability after exposure was
reevaluated.
Four dialysate filters that had been exposed to conditions which
caused them to release LAL-reactive material into throughput
solutions, were treated with a 250 ml 1:8 dilution Renalin.RTM. in
RO water solution and reverse flow conditions. Renalin.RTM.
residuals were rinsed to <1 ppm hydrogen peroxide. Endotoxin
retention capability was re-evaluated after rinsing has been
completed.
To produce this condition in which filters release or "shed"
LAL-reactive material, filters were run 24 hours/day at 800 ml/min
on a recirculation setup with contaminated dialysate. NOTE:
Shedding only occurs in filters that have not been periodically
re-sterilized during use (every 24-48 hours).
It was observed, that at a point between 10,000 liters and 20,000
liters total dialysate throughput, the filters began "shedding"
LAL-reactive material into the filtrate.
Before the re-evaluation of endotoxin retention was conducted, all
four units were pre-treated on the "recirculation" setup until they
began to "shed" LAL-reactive material into throughput solutions.
"Shedding" was verified using gel-clot LAL assays of filtrate
samples.
Once "shedding" was verified, all four units were exposed to a
Renalin Concentrate disinfection treatment.
The Renalin.RTM. membrane disinfection and clearing procedure
consisted of the following steps:
a. Removing the filter from the recirculating setup.
b. Installing it in reverse configuration (to "blow off" the
material impacted on the membrane surface) on a Travenol 450 SPS
dialysis machine, in between the dialysate in-flow and out-flow
lines.
c. Running RO water through the filter at 600 ml/min during a
Renalin.RTM. Concentrate chemical treatment on the dialysis
machine.
1) Allowing the dialysis machine to draw up 250 ml of Renalin.RTM.
Concentrate through the acid concentrate uptake line (resulting in
a 1:8 dilution of Renalin.RTM. Concentrate in the filter and
machine dialysate lines).
2) Turning off the dialysis machine and allowing the diluted
Renalin.RTM. Concentrate to dwell inside the filter for 30
minutes.
3) Turning on the dialysis machine and "rinsing" the filter with RO
water until <1 ppm of Renalin.RTM. was detected. This took about
20 minutes to accomplish.
d. Re-orienting the filter to normal flow direction and installing
it on the endotoxin challenge test bench.
After the Renalin.RTM. treatment, all four filters were installed
one-at-a-time on the endotoxin challenge test bench in preparation
for the post-treatment LPS retention test.
This endotoxin test setup consisted of a roller pump, inlet and
outlet tubing and Hansen-style connectors, pre- and postfilter
sampling ports, and 21/2 gallon polyethylene containers for holding
the challenge solutions. All tests used DI water throughput at a
flowrate=500 ml/min.
Again, the gel-clot method of Limulus Amebocyte Lysate endotoxin
assaying was used to analyze all samples for presence, absence, or
quantification of endotoxin.
Frozen, dried lipopolysaccharide (LPS, endotoxin), isolated from
Escherichia coli by phenol extraction, was reconstituted per the
manufacturer's instructions and added to a 21/2 gallon container of
pyrogen-free RO water immediately prior to initiating the test. The
21/2 gallon container was vigorously shaken and then placed on a
magnetic stirring platform, with a stirring bar in the bottom, to
help keep the solution mixed.
Once the LPS contamination was initiated, samples were collected
from filter inlet and outlet sample ports at T=1, 3, and 5
minutes.
Filters subjected to a Renalin.RTM. membrane clearing and
disinfecting procedure and receiving follow-up endotoxin challenges
varying in potency had the following .[.resutls,.]. .Iadd.results
.Iaddend.with a challenge from .gtoreq.7.7 EU/ml up to 30.7 EU/ml
of Escherichia coli endotoxin in RO water at throughput flowrates
of 500 ml/min, each filter retained all endotoxin contained within
the challenge solution. No detectable endotoxin is reported as
<0.06 EU/ml, the limit of sensitivity for the Lysate used in the
assay. (See Table below for details.)
TABLE XV ______________________________________ Recovery of
Endotoxin Retention After Renalin .RTM. Exposure "Shedding" LAL-
reactive Endotoxin Material Challenge before Level, Endotoxin
Filtrate Renalin .RTM. EU/Ml Level, EU/ml Filter Treatment
Treatment ? (After 1 3 5 # conditions (Y/N) Renalin .RTM.) MIN MIN
MIN ______________________________________ 1 20,000 liters Yes,
15.4 <0.06 <0.06 <0.06 recirculated >0.06 EU/ml
dialysate, then Renalin .RTM. treated 2 20,000 liters Yes, 15.4
<0.06 <0.06 <0.06 recirculated >0.06 EU/ml dialysate,
then Renalin .RTM. treated 3 20,000 liters Yes, 7.7 <0.06
<0.06 <0.06 recirculated >0.06 EU/ml dialysate, then
Renalin .RTM. treated 4 20,000 liters Yes, 30.7 <0.06 <0.06
<0.06 recirculated >0.06 EU/ml dialysate, then
Renalin .RTM. treated ______________________________________
Example 28
A filter as described in Example 8 was exposed to an amount of
bleach contact consistent with normal dialysis machine "low-level"
disinfection, and, a clearance curve (ppm vs. time) of residual
free chlorine levels during 500 ml/min RO water throughput was
plotted.
A dialysate filter was installed on a COBE Centry 2 Rx dialysis
machine, and a bleach treatment was performed as described in the
COBE Centry 2Rx Operator's Handbook.
This treatment consisted of an exposure to a 1:8 dilution bleach
(0.65% sodium hypochlorite) in water solution while the filter was
installed on the dialysis machine.
At the end of the bleach treatment, samples of the filter's outlet
fluid were collected about every minute for 15 minutes.
These samples were analyzed using a Beckman DU-640
Spectrophotometer which had been calibrated to analyze free
chlorine levels in samples tested.
These results were plotted on a time vs. ppm free chlorine
concentration and the time required to rinse free chlorine to
levels <1 ppm was noted.
Free chlorine residuals rinsed from the filter down to 1.6 ppm
within 10 minutes at a 470 ml/min RO water throughput flow
rate.
Example 29
A filter as described in Example 8 was exposed to an amount of
Actril.RTM. contact consistent with normal dialysis machine
"low-level" disinfection, and, a clearance curve (ppm vs. time) of
residual hydrogen peroxide levels during 500 ml/min RO water
throughput was plotted.
A dialysate filter was installed on a COBE Centry 2 Rx dialysis
machine, and a chemical treatment was performed as described in the
COBE Centry 2Rx Operator's Handbook, substituting Actril.RTM. for
bleach as the chemical used.
This treatment consisted of an exposure to a 1:8 dilution
Actril.RTM. (0.1% hydrogen peroxide) in water solution while the
filter was installed on the dialysis machine.
At the end of the Actril.RTM. treatment, samples of the filter's
outlet fluid were collected about every minute for 15 minutes.
These samples were analyzed using a Beckman DU-640
Spectrophotometer which had been calibrated to analyze hydrogen
peroxide levels in samples tested.
These results were plotted on a time vs. ppm hydrogen peroxide
concentration and the time required to rinse hydrogen peroxide to
levels <1 ppm was noted.
Hydrogen peroxide residuals rinsed from the filter down to 0.6 ppm
within 10 minutes at a 470 ml/min RO water throughput flow
rate.
Although the description of the preferred embodiment has been
presented, it is contemplated that various changes, including those
mentioned above, could be made without deviating from the spirit of
the present invention. It is therefore desired that the present
embodiment be considered in all respects as illustrative, not
restrictive, and that reference be made to the appended claims
rather than to the foregoing description to indicate the scope of
the invention.
* * * * *