Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using disinfecting or sterilizing substance
Reexamination Certificate
1999-09-16
2002-10-22
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using disinfecting or sterilizing substance
C422S048000, C510S161000, C510S367000, C510S376000, C435S264000, C134S003000, C134S022130, C134S022190, C134S036000, C134S041000
Reexamination Certificate
active
06468472
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to chemical compositions and methods for using the compositions for cleaning and decontaminating dialyzers.
BACKGROUND
The medical industry and other industries utilize devices that are required to be cleaned and decontaminated. Cleaning is the removal of foreign material, including organic soil such as blood, feces, respiratory secretions, etc., from objects. It has been reported that failure to remove foreign material from a medical device such as an endoscope before a disinfection or sterilization process is likely to render the process ineffective. (Rutala, W A, APIC Guideline for Selection and Use of Disinfectants,
Am J Infect Control
, August 1996; Vol. 24,4:313-342). The presence of organic material or soil may contribute to the failure of disinfection by harboring embedded microbes and preventing the penetration of the germicide. Additionally, some disinfectants are inactivated by organic material (Martin, M A, Reichelderfer, M, APIC Guideline for Infection Prevention and Control in Flexible Endoscopy,
Am J Infect Control
, 1 994;22:19-38). Decontaminating is defined as the removal of hazardous or unwanted materials such as bacteria, mold spores or other pathogenic life forms and the like, with high-level disinfection and sterilization representing different levels of decontamination. High-level disinfection is a process that eliminates many or all pathogenic microorganisms, with the exception of bacterial spores, from inanimate objects. Sterilization is a process that completely eliminates or destroys all forms of microbial life, including fungal and bacterial spores.
High-level disinfection can be expected to destroy all microorganisms, with the exception of high numbers of bacterial spores. A Food and Drug Administration (FDA) regulatory requirement for high-level disinfectants is that they achieve 100% kill of 100,000 to 1,000,000 organisms of
Mycobacterium tuberculosis
in the presence of 2% horse serum in a quantitative tuberculocidal test. An additional FDA regulatory requirement for high-level disinfectants is that they must also achieve sterilization over a longer exposure time than the disinfection regimen time. Sterilization is tested with a sporicidal activity test utilizing spores of
Bacillus subtilis.
Common commercially available high-level disinfectants include glutaraldehyde solutions between 2.4-3.4%, which typically require activation with an alkaline buffer just prior to use. Also available are an acidic (pH 1.6-2.0) 7.5%
w/v
hydrogen peroxide (H
2
O
2
) solution (Sporox®, Reckitt and Colman, Inc.) and an acidic (pH 1.87) mixture of 1.0% H
2
O
2
plus 0.08% peracetic acid (PAA) (Peract™ 20, Minntech Corp. or CidexPA®, Johnson & Johnson). The minimum effective concentration of PAA for high-level disinfection at 25 minutes (min) and 20° C. is 0.05% (500 ppm) (Peract™). The minimum effective concentration of H
2
O
2
for high-level disinfection at 30 min and 20° C. is 6.0% (Sporox®).
High-level disinfecting solutions are also typically designed for a reuse option, depending upon the medical device. For example, a glutaraldehyde high-level disinfecting solution for endoscope reprocessing may be reused for as long as 28-30 days, while kidney dialyzers are disinfected with single-use solutions.
Kidney dialyzers pose an additional problem in high level disinfecting in that the materials utilized require particular performance criteria of the cleaning and disinfection solutions. Types of dialyzers include: (1) coil, which incorporates a membrane in the form of a flattened tube wound around a central, rigid cylinder core, with a supporting mesh between adjacent portions of the membranes; (2) parallel plate, which incorporates a membrane in tubular or sheet form supported by plates in a sandwiched configuration; and (3) hollow-fiber, which incorporates the semipermeable membrane in the form of the walls of very small fibers having a microscopic channel running through them. Most parallel plate and hollow-fiber membranes are made from cellulose acetate, cellulose triacetate, regenerated cellulose, cuprophan or polysulfone.
The semipermeable membranes used in dialyzers have large areas and high porosities, and after use become coated with blood proteins and other organic and cellular material. Dialysis fibers are also often clotted with blood cells, proteins and other debris. As a result, the membrane of a used dialyzer has a reduced capacity for dialysis and is highly susceptible to microbial growth. Effective killing of microorganisms on such a used membrane for the purpose of reusing the dialyzer is difficult to accomplish without damaging the membrane.
When initially introduced, dialyzers were one-use devices. Since 1980, dialyzer reuse has risen dramatically in order to reduce the overall cost to the patient and the health care delivery system. Hemodialyzers, reprocessed in conformance with the Association for the Advancement of Medical Instrumentation (AAMI) specific guidelines and performance tests, have an average use number, that is, the number of times a particular hemodialyzer has been used in patient treatment. This number has been increasing over the years, from a United States average of 10 reuses in 1986 to 15 reuses in 1996. The cost benefits achieved by reprocessing are significant. For example, a new dialyzer costs about $20-30. With reprocessing, a dialyzer can be used between 5-20 times without substantial loss of efficacy. The cost of reprocessing is approximately $6.60-7.72 per unit, including reprocessing solutions. The cost per reuse for reprocessing solutions is $0.99-1.14 (average $1.08). The amortized dialyzer cost per reuse is $1.35-2.00, based upon an average reuse of 15 times. Additionally, the cost per reuse for dialyzer hazardous medical waste disposal is $0.50-0.55, reuse technician labor costs are $14/hr, and the associated labor cost of manual cleaning/dislodging clots is $0.23. Accordingly, with reprocessing, the dialyzer cost per treatment is conservatively less than about $10, as opposed to $30 if a new dialyzer were used for each treatment. A typical patient receives approximately 156 treatments per year. In 1998 in the United States alone there were approximately 280,000 patients on hemodialysis, and about 86% of hemodialysis centers have a dialyzer reuse program. Therefore, there are about 35,060,480 reuses in the United States (280,000×0.86×(156−156/15)). The U.S. market for reprocessing solutions in 1998 is estimated to be $34.7-40.0 million.
In addition to cost savings with dialyzer reuse, there are health advantages. Researchers have determined that reused dialyzers significantly mitigate patients' “new dialyzer” symptoms as well as immune reactions that often occur. The inherent clinical advantage of reused dialyzers has been attributed to both the reduction in trace contaminants such as ethylene oxide sterilant, and to the masking of immune reaction sites located on the membrane surface by protein deposits.
Dialyzer reprocessing involves three basic steps: (1) cleaning, (2) dialysis efficacy confirmation, and (3) high-level disinfecting involving soak times long enough to achieve sterilization. The cleaning step involves removing residual blood, organic and cellular material from the blood side and removing dialysate from the dialysate side of the semipermeable membrane. A number of cleaning solutions are known, including sodium hypochlorite bleach, PAA and H
2
O
2
. Purified water has also been used for cleaning. The cleaning solution must be rinsed from the dialyzer, typically with water.
Sodium hypochlorite bleach at a concentration of 0.5-1.0%
w/v
for 3 min exposure is utilized for cleaning. However, significant decreases in patient urea and creatinine clearance have been observed with high-flux polysulfone (F80B) dialyzers reprocessed with formaldehyde and bleach (Murthy et. al., Effect of Formaldehyde/Bleach Reprocessing on In Vivo Performances of High-Efficiency Cellulose and High-Flux Polysulfone Dialyzers.
J Am Soc Nephrol
:464472
Huth Stanley William
Yu Zhi-Jian
Chorbaji Monzer R.
Metrex Research Corporation
Warden, Sr. Robert J.
Wood Herron & Evans LLP
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