CMS SOM App. H, Tag V336

494.50(b)(1)

11.3 Performance measurements

11.3.1 Performance test after each use

Total cell volume (TCV) may be used for hollow-fiber dialyzers. The acceptable TCV is at

least 80% of the original TCV. The dialyzer prescription should take into account the 10%

loss in clearance (20% loss in TCV) that may occur with dialyzer reuse.

Interpretive Guidance § 494.50(b)(1)

ANSI/AAMI RD47:2002/A1:2003

11.3 Performance measurements

The performance characteristics of dialyzers may change following reprocessing. The

ultrafiltration coefficient may increase or decrease. Clearances of small or large molecular

weight solutes may also increase or decrease depending on the chemicals, methods, and dialyzer

membrane used. The dialyzer labeling and medical literature should be consulted for

information related to changes in in vitro and in vivo performance.

AAMI Rationale for the Development and Provisions of this Recommended Practice

A.11.3 Performance measurements

The essential function of the hemodialyzer is mass transfer adequate to provide the prescribed

care to the patient. A change in TCV has been documented in the medical literature as an

indirect measurement with a close relationship to the retained mass transfer of small molecules

by the hemodialyzer, and may be used for routine testing of residual dialyzer performance.

A.11.3.1 Performance test after each use

Clearance, a measure of the solute transport of the hemodialyzer, should be maintained within

acceptable limits to ensure that dialysis is adequate to prevent uremic complications. Although

direct clearance measurements could be used to demonstrate compliance with the ± 10% change

in urea clearance, determining the urea clearance for each dialyzer reprocessed is impractical.

There are also indirect tests that reflect the mass transfer characteristics of a dialyzer, which

may be used in lieu of clearance measurements. A change in the residual TCV of hollow-fiber

hemodialyzers is the most widely used indirect test for changes in small molecule clearance. This

method has been shown to be a good index to monitor the solute transport capacity of the

reprocessed hollow-fiber hemodialyzer. The volume of a hollow-fiber hemodialyzer (TCV) is

readily measured in the clinical setting. When methods of reprocessing are used that do not

cause a significant change in the permeability or geometry of the membrane, a loss of TCV of

20% corresponds to a loss of urea clearance of less than 10%. Volume change is recommended

as a QC test only for hollow-fiber hemodialyzers because other hemodialyzer geometries do not

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have the relatively noncompliant blood compartment necessary for the validity of this

measurement in predicting solute transport.

The AAMI RDD Committee recognized that other factors can influence the effective clearance of

toxins during the dialysis session or can influence interpretation of the results. These factors

include the following:

• Fistula recirculation;

• Accurate blood and dialysate flow rates;

• Accurate time of dialysis;

• Compliance with dietary limitations;

• Selection of appropriate hemodialyzer type and blood and dialysate flow rates;

• Membrane surface coating that may affect higher molecular weight toxins;

• Variations in the original clearance of the hemodialyzer;

• Variations in the clearance of the hemodialyzer caused by reuse.

Users should be aware that the HEMO Study in 1999 identified both reductions and increases in

the clearance of ß2 microglobulin with the use of certain combinations of dialyzers, cleaning

agents, and reuse germicides.

Of particular concern to the AAMI RDD Committee were any variations in hemodialyzer

functions related to reuse procedures. Although cases have been documented, they are rare,

especially when compared to the frequency of other factors listed above. For this reason, the

AAMI RDD Committee strongly felt that the monitoring requirements of AAMI section 13 are of

great importance to use in conjunction with the individual hemodialyzer measurements

recommended in AAMI 11.3.

Additional Guidance:

Every dialyzer expected to be reprocessed must have its original total cell volume (TCV)

measured prior to the first use. “Dry pack” dialyzers, i.e., dialyzers used without preprocessing,

must be discarded after the first use and not reprocessed.

All staff who reprocess or reuse dialyzers must demonstrate understanding that a drop in TCV to

less than 80% of the dialyzer’s original volume requires the discard of that dialyzer, to prevent

that patient from receiving a less than adequate treatment. Staff must also be aware of other

criteria dialyzers must meet for continued reuse (e.g., limit on the number of times a dialyzer

may be reused, reasons for discard).

If a manual reprocessing system is in use, the graduated cylinder used for measuring TCV must

be emptied completely between uses and placed on a level surface to ensure accurate readings.

The reading should be made at eye level, and the operator should have charts available to use in

determining whether the remaining volume is sufficient (at least 80% of the original volume) to

continue using that dialyzer.

For automated systems, a system must be in use to validate that the volume measurements are

accurate.

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