[The technological progress in haemodialysis: on-line hemodiafiltration].

Abstract

Patients with the end-stage renal disease who demand replacement of renal function are faced with numerous concomitant diseases and conditions, as well as with the possible side-effects and complications of the dialysis procedure. Intradialytic complications include hypotension and cardiac arrhythmias caused by rapid changes in electrolyte concentration and volume status. Long-term complications include increased incidence of cardiovascular diseases, malnutrition and increased mortality. Two major mechanisms are involved in removal of uremic toxins through the dialysis membrane: diffusion and convection. Diffusion removes only low molecular weight substances, while larger molecules may be removed by convection which also enables larger ultrafiltration. Haemodiafiltration (HDF) combines diffusion and convection. Convective transport may be enhanced by increased volume of suspstitution fluid. In order to avoid impractical addition of solutes in the bags, online (OL)-HDF has been constructed. Substitution fluid is prepared directly in the dialysis machine, in non-limited quantity with high level of microbacterial purity. It is obligatory to employ high-flux dialysers, while it is necessary to achieve high ultrafiltration with transmembrane pressure < 300 mmHg, what demands appropriate hydraulic sieving potential and surface. Sieving coefficient must be high enough to enable passage of bigger toxins, but to prevent loss of albumin. Patients treated with OL-HDF have decreased incidence of hypotension, cramps and cardiac arrhythmias. Dialysis dose is 30% higher with significant decrease in the concentration of beta2-mycroglobulin. Additional effects are favourable profile of leptin, one of the regulators of nutritional status in dialysis patients, as well as the antiinflammatory effects.