Method of Dialyzer Cleaning and Frequency of Reuse

Several methods exist for cleaning hollow fiber dialyzers for reuse. How important is the cleaning procedure in determining the number of times a dialyzer can be reused?

It is not possible to give a simple answer to this question. The process of cleaning clearly affects the recovery of membrane function. However, the ques- tion of what is an acceptable range of performance (below which the dialyzer should be rejected) has not been resolved.

Unfortunately, few controlled prospective studies have been published comparing different methods of cleaning dialyzers. Dennis et al. (1) prospectively compared four methods of cleaning 'hollow fiber dialyzers (HFAK) and found significant differences in the number of reuses. The investigators compared cleaning with sodium hydroxide, hydrogen peroxide, water flush, and reverse ultrafiltration and then dis- carded dialyzers with a loss of fiber bundle volume exceeding 14 ml. They found that sodium hydroxide- cleaned dialyzers averaged 14.5 uses, reverse ultrafil- tration 6.4, hydrogen peroxide 5.7, and water flush 4.7 uses. Based on this study and our experience with reuse it can be stated that cleaning methods are one of the major determinants of the number of times a dialyzer can be used.

The obvious problem with this type of study is in establishing a point at which the reprocessed unit should be rejected due to inadequate recovery of performance. Clearance of small molecules are less sensitive than fiber bundle volume loss since in processed dialyzers the decline in fiber bundle vol- ume usually is more pronounced than is the reduc- tion in creatinine or urea clearance (1). The decline in large molecule clearances probably is a more sensitive indicator of membrane performance, but this measurement is difficult to obtain in the usual clinical setting and the interpretation, as well as its clinical usefulness, is controversial.

Bleach is also a commonly used cleaning agent and provides more thorough cleaning. .In the past it has been shown to degrade Cuprophane membranes,

and for this reason the study discussed above did not compare bleach with other methods (1). However, with newer, more resistant membranes, this agent needs to be compared with other cleaning methods in a controlled prospective fashion.

When selecting a cleaning procedure a trade-off exists along a continuum. At one end is "gentle cleaning" which is safe for the device but which may fail to clean it thoroughly, thus limiting the number of uses. At the other end is more effective cleaning (such as with bleach) which may either make the dialyzer so clean that the first-use syndrome may be seen or may even degrade the membrane thus influ- encing the safety and efficacy of the HFAK.

Both manual and automated methods of process- ing HFAK are in common use. It is generally be- lieved that automated methods provide more thor- ough cleaning and thus more uses. Good controlled studies to compare these two methods of processing HFAK have not been published. However in a na- tionwide survey, 38% of those centers using auto- mated cleaning averaged >10 uses per HFAK com- pared with only 25% of centers utilizing manual systems (2).

A standard reprocessing method which works for most patients and dialyzers could probably be im- proved considerably if it were individualized. This increase in number of uses might not represent an increase in true productivity if the method turns out to be more labor intensive.

The processing of high-flux dialyzers encompasses some additional issues and needs to be addressed separately.

Suhail Ahmad, Seattle, WA

References 1. Dennis MB, V i u o JE, Cole JJ. WestendorfDL, Ahmad S: A compar-

ison of four methods of cleaning hollow fiber dialyzers for reuse. Anij Organs 10448-451, 1986

2. Alter MJ, Favero MS, Miller JK, Coleman PJ, Bland LA: Reuse of hemodialyzers. Results of nationwide surveillance for adverse effects. J Am Med Assoc 2602073-2076, 1988

~~

Dialysis Clinic welcomes questions of general interest to the journal's readership. Questions should be typed, double- spaced and sent to Robert 1. Lynn. M.D., Assistant Editor, Seminars In Dialysis, Baumritter Kidney Center, Albert Ein- stein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461. Unpublished questions cannot be answered or returned. Authors of questions will be identified unless 0th- erwise requested.

The purpose of Dialysis Clinic is to educate and inform. not to give medical advice regarding a specific patient. Med- icine is complex and patient-specific advice requires more details, both in the question and the answer, than can be provided. Information offered here should be checked with appropriate sources before it is used in diagnosis and ther- apy.

125