QUALITY OF HEMODIALYSIS WATER - A 7-YEAR MULTICENTER STUDY

Since dialysis was introduced 30 years ago, constant progress in technology permitted shortening the length of hemodialysis (HD) sessions. Through growing concerns about the inadequacy of tap water for dialysate production, hospitals soon opted for water treatment systems dedicated to HD. Nonetheless, persistent bacterial contamination and the occurrence of pyrogenic reactions were reported in some HD centers. Several factors contributing to this situation were identified. After the introduction of highly permeable synthetic membranes in the late 1970s, microbiologic problems reappeared. Thus, in 1977, the Centers for Disease Control and Prevention (CDC) issued proposed guidelines for HD water quality, followed in 1981 by an American National Standard for HD water, issued by the Association for the Advancement of Medical Instrumentation (AAMI). This Standard was also followed in Canada up to 1986, at which time a National Standard for Canada was released by the Canadian Standards Association (CSA). This prompted the Laboratoire de sante publique du Quebec (LSPQ) to implement in the Province of Quebec a voluntary HD water quality monitoring program. All 36 HD centers in the Province agreed to participate. The program was launched in February 1987. Water was sampled monthly for bacteria over a 7-year period (February 1987 to January 1994), and every 3 months for pyrogen and chemicals. Participation was more than 95%. Bacteriologic samples were processed in duplicate on heterotrophic plate count agar by the pour plate technique. Incubation was for 48 +/- 3 hours at 35 +/- 0.5 degrees C, and the colonies were counted on a Quebec colony counter (New Brunswick Scientific Co, New Brunswick, NJ). Pyrogen determinations were made using the limulus amebocyte lysate (LAL) test on 1:20 sample dilution by the gel-clot method. Chemical elements were measured by inductively coupled plasma emission, graphite furnace absorption, conductivity, ultraviolet light absorption, or colorimetry. Only fully treated HD water samples were selected from the 11,000 water samples received. Of the 5,820 samples retained for this study, 3,547 were for bacterial, 1,112 for pyrogen, and 1,161 for chemical analyses. Overall compliance to the CSA Standard was 70% for bacteria, 56% for pyrogen, and 86% for chemistry. The performance of different types of water treatments were compared and discussed; the best overall compliance was obtained by reverse osmosis combined with deionization (RO + DI). The type of water treatment that proved most popular was RO alone, which was used by 22 HD centers (61%). It was concluded that current technology made it possible to produce treated water that regularly met all the requirements of the CSA Standard for HD purposes. To achieve this, a rigorous disinfection and maintenance program of all the components in the water treatment system was primordial. We recommend reformulating the maximum acceptable limit of the CSA Standard for bacteriology, as well as allowing use of nutrient-poor media in an effort to improve bacterial recovery from treated water samples. (C) 1995 by the National Kidney Foundation, Inc.