Advancement Of Medical Instrumentation Standards Research Articles

An outbreak of pyrogenic reactions in chronic hemodialysis patients associated with hemodialyzer reuse.

In February 1992, 22 patients undergoing chronic hemodialysis at an outpatient dialysis center experienced pyrogenic reactions (PR). The PR rate was significantly greater (p < 0.001) during the epidemic (February 3-5) than the pre-epidemic period (November 1, 1992-February 1, 1992). All patients with PR used dialyzers that had been manually reprocessed either on February 1 or 3. These dialyzers contained up to 120.8 EU/ml of endotoxin in the blood compartment. The only dialyzer reprocessed before February 1 that was available for analysis was found to contain no detectable endotoxin, while dialyzers reprocessed during the epidemic period contained a median endotoxin concentration of 52.8 EU/ml. The bioburden of water used to prepare dialysate was in excess of the Association for the Advancement of Medical Instrumentation (AAMI) standard for water, < or = 200 colony forming units (CFU)/ml. Samples of treated water collected in the reuse area were within AAMI standards at the time of the investigation (February 11 and February 26), but before the investigation, water samples were assayed with a culture method that could not detect microbial concentrations below 10(3) CFU/ml. In addition, the treated water feed line to the disinfectant container may never have been disinfected. However, no samples were collected from this line during the investigation. This outbreak emphasizes the need to use water that meets the AAMI bacteriologic and endotoxin standards of < or = to 200 CFU/ml and/or 5 EU/ml, respectively, for reprocessing hemodialyzers nad to ensure that appropriate culture techniques are used for treated water dialysate.

Microbiological and Endotoxin Assays of Hemodialysis Fluids

The potential for exposure of dialysis patients to greater levels of microbial and endotoxin contamination has increased dramatically during the last decade with the increase in reuse of hemodialyzers, and the use of bicarbonate dialysate and high flux dialysis. To help prevent pyrogenic reactions and bacteremia in hemodialysis patients caused by microbial and endotoxin contamination of hemodialysis fluids, the Association for the Advancement of Medical Instrumentation (AAMI) has promulgated standards for maximum allowable concentrations of bacteria and endotoxin in these fluids. Each dialysis center should develop microbiological and endotoxin surveillance policies and procedures for the types of hemodialysis fluids to assay, frequency and manner of sample collection, assay techniques, and methods for recording and interpreting results to ensure compliance with the AAMI standards. These necessary components of a comprehensive surveillance program are discussed in depth in this article. A safer environment will be provided for each dialysis patient if appropriate microbiological assay procedures are followed and the results are consistently within the AAMI microbiological and endotoxin standards.

Outbreak of pyrogenic reactions and gram-negative bacteremia in a hemodialysis center.

Six episodes of gram-negative bacteremia and seven pyrogenic reactions occurred in 11 patients in one hemodialysis center. Gram-negative bacteremias and/or pyrogenic reactions were not related to reuse and were more likely to occur if dialysis was performed in one unit of the center (8/13 unit 5 vs. 221/1,151 in other units, p < 0.001) and with one type of dialysis machine (10/13 vs. 581/1,151 with other machines, p = 0.05), which was preferentially used in unit 5 (p < 0.01). Bacterial and endotoxin concentrations of water used to prepare dialysate and reprocess hemodialyzers, and of dialysate, exceeded allowable concentrations recommended by the Association for the Advancement of Medical Instrumentation (AAMI). The implicated dialysis machines were disinfected with chemicals daily, but not heat-disinfected daily as suggested by the manufacturer. Results suggest that the outbreak was caused by the use of water that did not meet AAMI standards and inadequate disinfection of one type of dialysis machine.

Formaldehyde, Sodium Hypochlorite, and Metabisulphite Are Equally Effective as Sterilants for Central Delivery Systems

Sterilants are used to disinfect reverse osmosis (RO) thin film composite membranes or peripheral loop water delivery systems. Formaldehyde (4.0% weight/volume) and metabisulphite (1.0%) were used to sterilize the RO and peripheral loop, and sodium hypochlorite (0.5%) was used to sterilize the peripheral loop with only acid/alkaline treatment of the RO; each sterilant was evaluated for 4 months. Sanitization at the machine was with sodium hypochlorite or glutaraldehyde. Quantitative RO processed water (weekly) and dialysate (4-6 from each station during the period of each sterilant) cultures were obtained. AAMI standards were used (< 200 CFU/ml RO water; < 2,000 CFU/ml dialysate). Bacterial growth exceeded Association for the Advancement of Medical Instrumentation (AAMI) limits in 16% of RO water and 4.7% of dialysate samples, but repeat cultures invariably failed to confirm initial abnormal results. Chi-square analysis showed no differences among sterilants. No difference among sterilants was noted in arithmetic or log10 mean colony counts. Sporadic low level gram positive and gram negative organism growth occurred with all sterilants. Continued "sterility" that met AAMI standards was obtained for 1 year, first with metabisulphite and then with acid/alkaline RO and sodium hypochlorite loop treatment. It is concluded that all three sterilants are effective for disinfection of hemodialysis delivery systems. Sodium hypochlorite is recommended because of its safety advantages and readily available test of adequate removal.