Water for the Production of Dialysis Fluid

Generally patients undergoing three times weekly dialysis treatments utilise dialysis fluid flow rates of between 500 and 800 ml/min, which corresponds to the use of 120-200 litres of fluid over a 4-hour treatment session. In contrast to the normal population, who not only are exposed to significantly lower volumes of water and in whom the gut offers a high degree of protection from impurities that may be present, dialysis patients are not only exposed to higher volumes of water, but during dialysis only the semi-permeable membrane present in the dialyser separates their blood from the dialysis fluid. Thus many of the permitted contaminants in drinking water have the potential to cause problems in dialysis patients (table 1). To minimise risks from such exposure, standards for water quality such as the AAMI/RD62 in the United States have been developed and implemented. These define the maximum permitted contaminants with compliance linked to reimbursement. The attainment of the required levels in the water used for the preparation of the dialysis fluid is by the additional water treatment, the nature of which is dependent upon the quality of the feed or raw water.

An emergent issue resulting from the removal of chemicals such as chlorine and chloramine, added as part of municipal water treatment to minimise bacterial proliferation, is that treated water is prone to bacterial proliferation unless appropriate disinfection and quality assurance systems are in place. The awareness of the importance of microbiology on patient mortality and morbidity has resulted in a harmonisation of microbiological standards regarding the quantification methods relating to water used in the preparation of dialysis fluid and in the introduction of more stringent limits for specific applications such as haemofiltration and haemodiafiltra-tion which mandate the use of ultra-pure water for the preparation of the dialysis fluid (table 2).

Table 3. Comparative composition of dialysis fluid and plasma

Dialysis fluid mEq/l

Plasma mEq/l

Electrolytes

Na

136-140

136-145

Cl

99-110

98-106

K

0-3.0

3.5-5

Ca

1.5

2.0-2.6

Mg

0.5-1.0

0.8-1.2

Buffer

Acetate

2.5-5.0

hco3

27-39

21-28

Glucose

2.0

0.8-1.2

0 0

Post a comment