Cleaning and liquid contact with solids – Processes – Hollow work – internal surface treatment
Reexamination Certificate
1999-12-13
2001-02-27
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Hollow work, internal surface treatment
C134S022180
Reexamination Certificate
active
06192900
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related generally to the field of reprocessing medical devices. In particular, it relates to a device and method for precleaning dialyzers and dialyzer headers including dialyzer header caps prior to reprocessing.
2. Description of the Related Art
Individuals requiring renal system support, or who have end-stage renal disease or acute or chronic renal failure, have kidneys that are temporarily or permanently incapable of removing products of metabolism and other substances from the blood for excretion in urine. Products of metabolism or metabolites typically include compounds such as urea, creatinine, natural biochemical metabolites, drug metabolites, and excess electrolytes. Individuals with end-stage renal disease may either undergo the replacement of a diseased kidney by transplantation of a healthy kidney, if available, or undergoing periodic hemodialysis (multiple weekly treatments) to reduce the concentration of harmful materials in the blood stream. Other individuals with trauma-induced acute renal failure need hemodialysis for brief periods of renal support.
Hemodialysis is a process in which solute molecules, which constitute undesirable waste products in human blood, are transported from the bloodstream across a hollow fiber membrane into a dialysis fluid concentrate. The aforementioned transport is accomplished by the difference in hydrostatic pressure across the membrane and the difference in chemical potential of each individual solute molecule across the membrane. Dialysis requires that membranes separating blood from dialysis fluid concentrate permit difflusional transfer of at least some of the molecular species present in blood into the fluid while effectively preventing any return contamination of blood or commingling of the blood and the dialysis fluid concentrate. Dialysis is a passive separation process with low operating costs using no external thermal or chemical energy sources. The basic hemodialysis separation obtained is between large cells and molecules, such as red blood cells, white blood cells, proteins, and small molecules such as urea, electrolytes, and other small molecule metabolites.
Hemodialysis machines control the rate of ultrafiltration while the dialyzer is the functional unit that provides a membrane capable of difflusion. Dialyzers utilize a hollow fiber membrane bundle of varying surface areas depending on the treatment modality. The generally accepted method of manufacturing hollow fiber filter dialyzers is to retain a rectilinear bundle of hollow fibers within a casing, immerse the longitudinal distal ends of the hollow fiber bundle into a potting compound which adheres to and abuts the inner surface of the casing occupying the interstitial void between the individual hollow fibers thus preventing blood contaminated with waste metabolites from coming into contact with the clean fluid concentrate or filtrate. A cross-sectional portion of the potting compound from both longitudinal ends of the potted fiber bundle is removed during the manufacturing process to provide access to the interior lumen of the individual hollow fiber membranes.
Each longitudinal end of the dialyzer is covered with a dialyzer header cap. The dialyzer header cap and the potting compound define the dialyzer header. Blood enters the dialyzer through the arterial dialyzer header cap, flows into the first dialyzer header, into the first end of the hollow fibers, through the hollow fibers, out the second end of the hollow fibers, into the second dialyzer header, and out the venous dialyzer header cap.
During dialysis, blood flows through the lumen of the hollow membrane while a dialysate fluid concentrate flows over and around the exterior surface of the hollow fiber membranes. As the blood flows through the lumen of the hollow fiber membrane, waste products from the blood diffuse through the hollow fiber membrane and into the dialysate fluid.
Everyday, dialysis centers reprocess used dialyzers so that they can be safely reused on the same patient. Reuse of dialyzers reduces healthcare costs by increasing the number of times each dialyzer may be reused before replacement. Although dialyzers can be reused on the same patient a significant number of times, dialysis centers set a predetermined maximum reuse limit as part of their dialysis procedures. However, most dialyzers fail before reaching the predetermined maximum use limit, which can vary anywhere from 10 to 100 times.
One of the major causes of premature failure is due to excessive volume loss or volume failure. Volume is used as a measure of dialyzer adequacy. Volume testing consists of measuring the total volume of the blood side of the dialyzer before it has been used and then comparing this first measurement to total blood side volume prior to each reuse.
Typically, each time a dialyzer is reused a portion of the total volume is lost. Loss of volume has been correlated to loss of mass flow transfer and loss of dialyzer efficacy. The dialyzer “fails” if the volume is less than 80% of the initial volume.
Blood clots, debris, proteins, lipids, fibrous biomasses, and other buildup within the dialyzer typically causes volume failure. The buildup also can cause blockage of the lumen of the hollow fibers. As hollow fibers become blocked or covered over repeated reuses, the total volume decreases. One factor causing loss of volume is the buildup of the aforementioned substances in the dialyzer headers including the openings to the hollow lumens. Once a hollow fiber is plugged, the reduced flow through the hollow fiber causes the other end to plug as well. Typically, once a hollow fiber is plugged, its volume is lost and further reuse is precluded.
Continual buildup may also cause secondary membrane formation. Proteins, lipids, and other such by-product masses may cause a membrane-like buildup, called a secondary membrane, to form in the dialyzer header and within the lumens of the hollow fiber membranes. This type of buildup can be difficult to remove, particularly after a number of reuses. Secondary membrane formation may cause further loss of volume and the loss of mass transfer.
Buildup in the dialyzer header, including secondary membrane formation, may also cause the loss of adequate access to the lumens of the hollow fibers for fiber cleaning. Before the lumens of the hollow fibers can be cleaned, any blockages at the ends of the hollow fibers have to be cleared away as much as possible. If the ends of the hollow fibers are plugged or partially blocked, the lumens cannot be properly flushed and cleaned. Failure to adequately remove buildup from the dialyzer header directly impacts the ability to flush and clean the hollow fibers. Once the dialyzer header has been adequately cleared of debris and buildup, the hollow fibers can be cleaned.
Continual failure to provide adequate and consistent removal of the buildup in dialyzers results in premature volume failure. As premature volume failures increase, the average number of reuses per dialyzer decreases. The average reuse number of dialyzers directly impacts healthcare costs. The average reuse of dialyzers is about 14 reuses; well short of the 25 to 35 times typically set as a maximum reuse limit.
Many dialysis technicians attempt to solve the aforementioned problems associated with reuse by manually precleaning the dialyzers before the dialyzers are sterilized and reused on patients.
In some cases, technicians remove the dialyzer header caps from the dialyzers to remove buildup, or place foreign objects into the dialyzer headers through the dialyzer header caps to clean out the buildup. These practices may result in cross-contamination or damage to the dialyzers.
If the dialyzer header caps are removed, the dialyzers are open to the clinic or hospital environment and blood may be accidentally spilled or sprayed on surrounding equipment, personnel or patients. In some cases, technicians flush open dialyzers at sinks, risking exposure to splashed or sprayed blood from the dialyzers. The expos
Andrus Robert G.
Arnal Kevin R.
Luhring David A.
Toy Jeffrey C.
Chaudhry Saeed
Gulakowski Randy
Minntech Corporation
Wrigley Barbara A.
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