Hemodiafiltration with online regeneration of the ultrafiltrate

The concept of regeneration of dialysis fluids and of ultrafiltrate in part icular has been recently revisited. Hemodiafiltration with online regenerat ion of the ultrafiltrate allows the concomitant infusion of sodium, calcium , and bicarbonate. Here, we studied the adsorptive characteristics of an in tegrated two-step sorbent system relative to different solutes present in t he ultrafiltrate: sodium, calcium, phosphate, bicarbonate, uric acid, creat inine, and beta(2)-microglobulin. In vitro studies were performed in order to differentiate the relative roles for each sorbent (mineral-activated cha rcoal or hydrophobic resin) in adsorbing st given solute. Ex vivo studies w ere performed in order to evaluate the presence of cytokines (interleukin-1 beta and tumor necrosis factor-alpha), of cytokine (interleukin-1 beta and tumor necrosis factar-alpha)-inducing activities, and of the cytokine rele ase in response to exogenous bacterial lipopolysaccharide by normal whole b lood incubated with ultrafiltrate samples obtained at 15, 120, and 240 minu tes after the start of treatment. The results of the present studies show t he presence of immunomodulatory substances in the ultrafiltrate and the sig nificant (P < 0.01) increase in the lipopolysaccharide-induced release of b oth interleukin-1 beta and tumor necrosis factor-alpha. The biological rele vance of the ultrafiltrate and the possible relevance of the online, endoge nous reinfusion are discussed.