Is the Type of Hemodialysis Important to Control Serum Phosphate?

not effi cacious if not associated with dietary restriction and P binders. In this issue of Blood Purifi cation , Bolasco et al. compared P kinetics in standard HD and on-line hemodiafi ltration with endogenous reinfusion (HFR) by using a new method to measure P levels into the dialysate. This issue is of interest because sensitivity of the common automatic analyzers is inadequate to precisely quantify the low P concentrations into the dialysate. Nevertheless, from the clinical point of view, the most important fi nding of the study is that the dialytic P removal by HFR was comparable to that obtained by standard HD, and that both types of dialysis allowed to maintain the plasma P levels below the recommended target in most patients [4] . However, HFR also decreases infl ammatory stimuli because of purity of reinfusion solution, adsorption of infl ammatory cytokines by resin and optimal balance of bicarbonate [5] . This point is critical; in fact in uremic patients, infl ammation and metabolic acidosis worsens nutritional status. Taken together, these fi ndings suggest that HFR may be an option more suitable than standard HD to ameliorate P balance in the subset of patients with impaired nutritional status or signs of systemic infl ammation. Long-term controlled studies on this issue are still required to verify this hypothesis. Of note, standard hemodiafi ltration techniques (HDF), where ultrafi ltrate is not reinfused, signifi cantly increase P removal, of about 40% versus HD, because of A high serum phosphate (P) level is an independent determinant of morbidity and mortality in hemodialysis (HD) patients, with values of 4.5 mg/dl to be considered as the ideal target [1, 2] . To date, however, the therapeutic interventions have generally failed with about 50% of patients showing predialytic p values 1 5.5 mg/dl [2, 3] . Prevention of hyperphosphatemia is based on restriction of dietary P intake and reduction of intestinal absorption of P; however, both the therapeutic approaches are weakened by major drawbacks. Indeed, lowering of protein intake ! 1.0 g/kg b.w./day to reduce dietary P is not safe since this is the minimum level to avoid malnutrition in HD patients; HD, in fact, induces protein catabolism by means of loss of amino acids and albumin, and by infl ammatory stimuli as well. On the other hand, use of P binders to decrease absorption may be associated with detrimental effects dependent on excessive load of aluminum or calcium; a more valid alternative is likely represented by the new generation of calcium and aluminum-free agents but compliance to prescription is often hardly achieved for these drugs. On the basis of these observations, the role of dialytic removal in the achievement of adequate P levels becomes relevant. Standard 4-hour HD allows to remove about 800 mg/session, that is, 2,500 mg in 1 week. This amount is almost half of the quantity of P derived from a normal protein intake. Therefore, standard intermittent HD is Published online: February 10, 2006