A dialysis facility may use dialyzers for the same patient for multiple treatments. Dialyzer reuse can be a safe and effective practice. As the cost of high-flux, biocompatible dialyzers has come down, prevalence of reuse in the United States has fallen from 78% of facilities in the mid-1990s to about 50% of facilities (47% of patients) in 2013 (Upadhyay, 2007; Neumann, 2013). Only hollow-fiber dialyzers, labeled by the manufacturer for multiple use, may be reprocessed.

I. REPROCESSING TECHNIQUE. To use a dialyzer multiple times, the dialysis unit must meticulously follow the standards set out by the Association for the Advancement of Medical Instrumentation (ANSI/AAMI RD47:2002/A1:2003). These AAMI standards are incorporated in the Medicare ESRD Facility Conditions for Coverage (ESRD Interpretive Guidance, V304-V368). Some of the text and language in the Medicare conditions differs from the text and language in the AAMI document; however, the Centers for Medicare and Medicaid Services (CMS) holds the facility accountable for the text and language in the AAMI document.

While it is possible to accomplish safe and effective reprocessing using a manual technique, the preponderance of reprocessing is done with automated equipment. Several types of automated machines are now manufactured. Some machines provide the ability to process multiple dialyzers simultaneously. With automated methods, the cleansing cycles are reproducible and a variety of quality control tests measuring total cell volume (TCV) (fiber bundle volume + volume in the headers), ultrafiltration coefficient, and the ability of the reused dialyzer to hold a pressure applied to the blood compartment are built in. Automated equipment also facilitates printing of dialyzer labels and computerized analysis of records and testing results.

Any medical director wishing to use a manual system must validate each step of the process and design appropriate quality control steps and audits to assure adherence and consistency. On the other hand, any automated equipment used must have a U.S. Food and Drug Administration (FDA) 510(k) clearance. (A 510[k] is a pre-market submission made to FDA to demonstrate that the device to be marketed is at least as safe and effective as; that is, substantially
equivalent to, a legally marketed device that is not subject to pre-market approval.) It is incumbent on the medical director using automated equipment to follow the manufacturer’s directions for use.

Reprocessing can be divided into three phases: pre-first-use, the dialysis treatment, and postdialysis.

A. Pre-first-use. The dialyzer is recorded into inventory, assigned to a patient (at which time it is indelibly labeled with patient name, noting whether there are any similarly named patients in the dialysis unit). Prior to initial use, the dialyzer is preprocessed to measure the baseline TCV. During preprocessing, the dialyzer is rinsed, pressure-tested, and filled with a germicide.

B. The dialysis treatment. Prior to allowing a reprocessed dialyzer to be used on a patient, the patient care provider (PCP) should inspect the dialyzer to be sure that it is not discolored, leaking, or showing significant clotting of fibers in the header. The facility medical director should establish a definition of “significant clotting” to guide staff. Peracetic acid has no vapor pressure and depends on direct contact to be effective; if peracetic acid was used to disinfect the dialyzer, the PCP must assure that a sufficient volume of disinfectant fluid was present in the dialyzer to assure direct contact. This is done by examining the air-fluid level in the headers when the dialyzer is held horizontally: both headers should be at least two-thirds full. The PCP must confirm that there is germicide in the dialyzer, that the contact time of the dialyzer with the germicide exceeds the minimum number of hours required for that particular germicide, and that the dialyzer has passed all the required performance tests. The presence of germicide is confirmed by using a test strip of appropriate sensitivity. The PCP then primes the dialyzer with normal saline and starts a recirculating rinse, with minimal ultrafiltration, at a blood compartment recirculating flow rate of at least 200 mL/min, while flowing dialysate through the dialysate compartment at 500 mL/min or more. This rinse is continued for 15-30 minutes. It is important to avoid introducing air into the arterial circuit during this rinsing process, as any air trapped in the fibers or dialysate compartment may reduce the effectiveness of germicide removal. The dialyzer should be rotated at intervals during flushing to release trapped air in the dialysate compartment. After the rinse, the PCP must assure that the dialyzer, extracorporeal circuit, and saline bag are free of residual germicide by use of a test strip of appropriate sensitivity.

After rinsing has been completed, if the start of the treatment is delayed for some reason, before putting the patient on dialysis, the PCP should retest for a “rebound” of germicide caused by either the dialysate or saline flow being interrupted while the dialyzer is in standby. The medical director should set guidelines for the dialysis unit, specifying how long a dialyzer, once it has been set up for a patient, can sit on the machine before it is deemed unsuitable for use without a repeat cycle of reprocessing.

Before the PCP starts the treatment, two PCPs should perform a “time-out,” during which they follow a checklist assuring that critical elements of the dialysis prescription are correctly set for this patient’s treatment. For reuse, the critical elements are that this dialyzer is for this patient, that it is the correct model dialyzer, that it had the appropriate contact time with the germicide, that it is now free of germicide, and that information on the reprocessing label confirms that the dialyzer is safe to use. If possible, it is desirable that the patient participate in this step. Both PCPs should sign off on the safety checklist.

C. Postdialysis. At the end of a treatment, the PCP returns the blood in the dialyzer to the patient in such a way as to minimize the amount of blood left in the dialyzer. The PCP or the reuse staff transports the dialyzer to the reprocessing area, making sure that the dialyzer ports are capped and that there is no cross-contamination with other dialyzers that are being transported at the same time. The dialyzer is then rinsed, cleaned, tested, disinfected, inspected, labeled, and stored until the next use. The medical director must validate any practices in the reuse process that are not explicitly described in the AAMI standards or the dialyzer manufacturer’s “directions for use.”

1. Rinsing and reverse ultrafiltration postdialysis. To maintain the patency of fibers and to minimize clotting after dialysis, blood can be returned with heparinized saline. Once the patient has been detached from the extracorporeal circuit, the PCP can add positive dialysate pressure to force residual blood from the fibers. If, after use, a dialyzer cannot be promptly reprocessed, the dialyzer should be refrigerated in a temperature-monitored container (avoiding freezing) within 2 hours (AAMI RD47:2002). Facility practice as approved by the medical director should set limits for how long the dialyzers can be refrigerated before being reprocessed or discarded. Typically, this maximum time varies between 36 and 48 hours from the end of treatment. The staff may not refrigerate a dialyzer that has been exposed to rinsing with nonsterile RO (reverse osmosis) water; while AAMI standards do not require water used in rinsing to be sterile, once the blood compartment has been exposed to other than sterile fluids, the dialyzer must be promptly reprocessed.

2. Cleaning. Typically, this is accomplished in two steps. The first involves an initial rinsing of the dialyzer and cleaning the headers with RO water. The second is to put the dialyzer on a machine (or through a manual process) that further rinses and cleans the fibers using one of a number of chemical cleaning agents.

a. Water. Water used for rinsing and reprocessing must, at a minimum, meet AAMI standards. The current Medicare “conditions for coverage” (ESRD Interpretive Guidance, V176-V278, 2008; ANSI/AAMI RD52: 2004) requires adherence to the AAMI standards current in 2008 when the conditions were published. In 2008, those standards specified a bacteria upper limit of <200 cfu/mL
(colony forming units/mL) and an endotoxin upper limit of <2 eu/mL (endotoxin units/mL). The action levels were <50 cfu/mL and <1 eu/mL, respectively. These are the standards that Medicare surveyors will enforce. However, in 2011, AAMI reduced the maximum allowable bacteria count in water to <100 cfu/mL and endotoxin to <0.25 eu/mL with action levels of <50 cfu/mL and <0.125 eu/mL, respectively. The new stricter limits also call for use of more rigorous microbiologic techniques and longer incubation times to assess the bacterial colony forming unit count. As of 2014, CMS has not revised the “conditions for coverage” to include these revised, more stringent, standards. The medical director approved policy and procedure should state explicitly what is meant by the phrase “AAMI standard” water. At a minimum, water used must meet the standards in the Medicare “conditions of coverage.”

b. Rinsing and reverse ultrafiltration. While this process may have been started with saline (heparinized or otherwise) while the dialyzer was still on the dialysis machine (see Section I.C.1), the most common practice is to put the dialyzer on a manifold that flushes AAMI standard water (see above discussion) through the blood and dialysate compartments for 20-30 minutes. During flushing, a positive pressure gradient from the dialysate to the blood compartments is maintained to help flush clots and plasma detritus from the blood circuit. The pressures in this manifold must not exceed those specified by the manufacturer’s directions for use to avoid rupturing or collapsing the hollow fibers.

During this cleaning step, staff inspect and clean the headers to remove lipids and clots. For dialyzers that do not have removable header caps, there are assist devices that use RO water to flush the headers. If the header caps are removable, they and the associated “O” rings can be removed, allowing a direct rinse of the exposed ends of the fiber bundle and potting compound.

Any procedure that invades the blood compartment risks cross-contamination. AAMI standard water, even as defined in the 2011 revision, is not sterile. If the procedure uses assist devices, it must specify that these devices be used on only one dialyzer before they are cleaned and soaked in an appropriate germicide. If the practice allows the removal of the header caps, they and their “O” rings must be exposed to a disinfectant (bleach or peracetic acid) before being replaced on the dialyzer. Staff must take care not to damage the end of the exposed fiber bundle. Failure to adhere to correct practices in the step of dialyzer header cleaning has frequently been the root cause of outbreaks of bloodstream infections and pyrogen reactions.

The current generation of reprocessing equipment is not able to effectively remove large amounts of clot and detritus from the fiber bundle or header. It is necessary
to subject the dialyzer to the precleaning steps described earlier. One novel machine for dialyzer reprocessing (ClearFluxTM, from the Novaflux corporation, Princeton, NJ) does not require a precleaning with nonsterile fluids before reprocessing. With this particular machine, the first step in reprocessing is to run a mixture of compressed air and a proprietary cleaning agent through the dialyzer; this mixture effectively removes clots from the dialyzer headers (Wolff, 2005).

c. Bleach. Sodium hypochlorite (bleach), diluted to 0.06% or less, dissolves proteinaceous deposits that may occlude dialyzer hollow fibers. The bleach used should be free of dyes or scents and be listed by the EPA as suitable for cleaning and disinfection.

d. Peracetic acid. Peracetic acid (mixture of acetic acid and hydrogen peroxide) is the most commonly used cleaning agent (HICPAC, 2008). Peracetic acid is available in proprietary and generic versions. Peracetic acid may not completely remove proteins deposited on the dialyzer membrane.

3. Tests of dialyzer performance. These check the integrity of the membrane, its clearance (TCV), and its ultrafiltration properties. The tests may be done manually or using automated techniques.

a. Pressure test for leaks. A blood path integrity test works by generating a pressure gradient across the membrane and observing for a pressure fall in either the blood or the dialysate compartment. The gradient may be produced by instilling pressurized air or nitrogen into the blood side of the dialyzer or by producing a vacuum in the dialysate side. Only minimal amounts of air should be observed to leak through an intact wetted membrane; damaged fibers usually rupture when a transmembrane pressure gradient is applied. Leak tests also screen for defects in the dialyzer O-rings, potting compound, and end-caps.

b. Blood compartment volume. This test indirectly measures changes in membrane clearance for small molecules such as urea. The blood compartment volume (TCV) is measured by purging the filled blood compartment (header volume and fiber volume) with air and measuring the volume of obtained fluid. Every dialyzer destined for reprocessing should be processed before its initial use in order to measure a baseline TCV for that particular dialyzer. The change in TCV from baseline is then tracked by remeasuring TCV after each reuse. A reduction in TCV of 20% corresponds to a 10% reduction in urea clearance, the maximum decrease acceptable for continued use. In a given patient, repeated failure to reach a target number of reuses because of TCV test failures suggests excessive clot formation during dialysis and should prompt a review of the heparin prescription.

c. Water permeability (in vitro K_UF). The dialyzer ultrafiltration coefficient (K_UF; described in Chapter 3) measures water permeability but is also an indirect measure of membrane mass transfer properties for larger molecular weight substances. The in vitro K_UF can be measured by determining the volume of water passing through the membrane at a given pressure and temperature. Changes in K_UF do not affect fluid removal during dialysis, as most dialysis being done today uses machines with automated ultrafiltration control that will compensate for even moderate decreases in water permeability with appropriate adjustments in transmembrane pressure. However, a decrease in K_UF usually is accompanied by a reduction in β₂-microglobulin clearance.

d. Clinical confirmation. Online, conductivity determined sodium or ionic clearance, which is comparable to urea clearance, or online measurement of other proxies of urea clearance are other acceptable methods of monitoring dialyzer performance (AAMI RD47:2002). Such online clearance measurements are done during the dialysis treatment and require a process of record keeping to track and compare them with reuse numbers or TCV.

The facility QAPI (QAPI = Quality Assurance/Performance Improvement) team can correlate the laboratorymeasured Kt/V with the reuse number across all patients in the dialysis unit, or it can investigate failures to deliver adequate Kt/V or URR as a function of reuse history in a given patient. The QAPI team must show that reuse is not adversely affecting dialysis efficiency.

4. Disinfection/sterilization. Once cleaned, the dialyzer must undergo a chemical (germicide) or physical (heat) process that renders all living organisms inactive. High-level disinfection differs from sterilization in that the former may not destroy spores. High-level disinfection is all that current standards require. Sterilization as defined legally is not easily accomplished in a dialysis facility.

a. Germicides. After a dialyzer has been cleaned and tested, germicides are instilled in both blood and dialysate compartments for an appropriate contact duration (see Section I.C.7). Peracetic acid is the most common germicide used. The use of formaldehyde or glutaraldehyde has essentially disappeared, probably because there are no automated methods for dialyzer reprocessing using formaldehyde or glutaraldehyde, and because manual methods for aldehyde chemical reuse are burdensome, having to meet U.S. Occupational Safety and Health Administration (OSHA) standards for safe handling, attention to exposure limits, and surveillance and respiratory testing for exposed staff.

b. Documenting the presence of germicide. The presence of germicide must be ensured through procedural controls
and should be verified both at the completion of reprocessing and prior to use (see Section I.B). The presence of peracetic acid is confirmed using test strips. If formaldehyde is used, FD&C (U.S. Food, Drugs & Cosmetic Act) blue dye can be put in the concentrated (37%) formalin to give the dialyzer a light blue color once the formaldehyde is diluted. In manual reprocessing systems, each dialyzer must be checked for the presence of germicide. In automated systems, only a sample needs to be tested each day.