TRACE ELEMENTS IN PATIENTS TREATED BY ON-LINE HEMODIAFILTRATION The Blood Chromium Behaviour

The interest in trace elements in haemodialysed (HD) patients has been generated by the recognition that Al accumulation may cause toxicity. Anomalies of other trace elements in specific tissues are however commonly presents in HD patients (Gallieni, Brancaccio and Cozzolino, 1996) although the clinical relevance of these abnormalities remains unclear. Recent attention has been devoted to elevated level of Chromium in tissues of HD patients (Wallaeys et al., 1986) in contrast with very low essential levels in normal subjects (Minoia et al., 1990). A study by Wallaeys et al. described the pathways involved in transport of Cr across the dialysis membrane (Wallaeys, Cornelis, Sabbioni, 1988). Padovese et al. confirmed that fresh peritoneal dialysate contained a Cr level 17 fold above the indicative reference plasma Cr concentration (Padovese et al., 1992). Borquet et al. studied the kinetics of Cr in Continuous Ambulatory Peritoneal Dialysis patients (Borguet et al., 1996) and justified, with mathematical models, Cr accumulation in blood and tissues. In haemodiafiltration (HDF), the reinfusion fluids and large membrane pores, which allow the passage of larger protein molecules, are additional factors influencing the balance of trace elements (Van Renterghem, Cornelis and Vanholder, 1992). Accumulation or depletion of trace elements may be more relevant if we use large quantities of reinfusate, as in the case of on-line production of reinfusate (Canaud et al., 1998). For these reasons we studied Cr levels in patients treated by HDF with large amounts of on-line produced reinfusate and dialysate. We compared Cr whole blood concentrations with those of our HD patients and studied Cr concentrations in on-line HDF patients through an extended period. In order to guarantee safety of HDF patients, other trace elements, as well as Cr, were monitored both in blood and in dialysis fluids.