Trace element status in hemodialysis patients.

Patients with chronic kidney disease undergoing hemodialysis (HD) are potentially at risk of deficiency and excess of trace elements. HD exposes patients to large volumes of water (>120 l/week) in the form of dialysate. Although levels of certain ions (such as potassium and calcium) are carefully regulated in dialysate, many others are measured infrequently, if ever. As a result, substances in lower concentrations in the dialysis may be leached from the body. Conversely, toxic trace elements present in water but not in blood may accumulate and cause toxicity. Given that essential trace elements play key roles in multiple biological systems including immunological defense against oxidation and infection, it has been hypothesized that the increased morbidity and mortality seen in HD patients may in part be due to the imbalance of trace elements that has not been recognized. A recent systematic review has shown that compared with healthy controls, HD patients have significantly lower blood levels of zinc, manganese, and selenium, while blood levels of lead are likely to accumulate. Other trace elements, such as mercury and arsenic, are biologically plausible causes of excess mortality in dialysis patients, but available evidence is inconclusive as to whether they consistently accumulate in this population. Whether altered trace element levels are potentially reversible causes of adverse clinical outcomes in dialysis patients remains to be determined. This review highlights key issues related to this hypothesis, with special emphasis on zinc, manganese, selenium, lead, mercury, and arsenic.