Adequacy of dialysis: trace elements in dialysis fluids

Abstract

A number of considerations suggest that trace element disturbances might occur in dialysed patients. These must at least in part be ascribed to the dialysis treatment itself during which these constituents may either be transferred to or removed from the patient. Tap water must be considered as the main source of dialysate trace metal contamination. These can adequately be removed during water treatment provided that, in addition to softening and deionization, reverse osmosis is available. However, even in the presence of the latter devices the possibility of serious contamination of the dialysis fluids leading to either chronic or acute intoxications still exists. The addition of chemical concentrates may also contribute to the increased concentrations of a number of trace metals. The toxic effects of aluminium in dialysis patients are well known and at the present time the element is still responsible for the greater part of trace metal-related problems in dialysis patients. Hence, the need for regular monitoring of aluminium cannot be ruled out at present. Strategies for diagnosis and treatment of aluminium overload have been updated. Recent studies demonstrated the efficacy of low desferrioxamine doses in diagnosis and treatment of aluminium overload, and optimal schedules for administration of the chelator and duration of treatment have been presented. Recently, in an epidemiological survey serum silicon concentrations in dialysis patients were found to be increased up to 100-fold compared to subjects with normal renal function. Moreover, it was noted that silicon concentrations in the dialysis population differ from one centre to another and that increased levels are due to either the use of silicon-contaminated dialysis fluids or an increased oral intake of the element originating from a high silicon content in the drinking water. Besides aluminium and silicon, a transfer towards the patients during dialysis has also been reported for a number of other elements including copper, zinc, nickel, strontium and chromium. The possible consequences of dialysate contamination with these elements will briefly be dealt with in the present paper. In contrast to trace metal accumulation, removal of trace metals during dialysis may at least in part contribute to the relative deficiency of particular essential elements. Selenium deficiency has repeatedly been observed. In view of the element's well-known essential role in glutathion peroxidase activity and the association of its deficiency with the development of some malignant diseases, further studies on the clinical impact of decreased serum selenium in dialysis patients are worthwhile. In conclusion, trace metal dialysate contamination/ depletion may contribute to the disturbed trace element concentration in dialysis patients. Aluminium accumulation is still an important problem in clinical nephrology. The clinical importance of the accumulation/ deficiency of trace elements other than aluminium is not yet fully understood and deserves further investigation.