Dialysis adequacy and response to erythropoiesis-stimulating agents: what is the evidence base?

Despite an increase in the use and average dose of erythropoiesis-stimulating agents (ESA) over the past 15 years, a substantial percentage of patients still do not achieve hemoglobin targets recommended by international guidelines. A clear relationship among hemoglobin or hematocrit levels, ESA dose, and increase in dialysis dose has been pointed out by a number of prospective or retrospective studies. This is particularly true in patients receiving inadequate dialysis. Increasing attention also has been paid to the relationship between dialysis, increased inflammatory stimulus, and ESA response because dialysate contamination and low-compatible treatments may increase cytokine production and consequently inhibit erythropoiesis. The biocompatibility of dialysis membranes and flux are other important factors. However, in highly selected, adequately dialyzed patients without iron or vitamin depletion, the effect of these treatment modalities on anemia seems to be smaller than expected. The role of on-line treatments still is controversial given that it is still difficult to discriminate between the effect of on-line hemodiafiltration per se from that of an increased dialysis dose. Very preliminary results obtained with short or long nocturnal daily hemodialysis on anemia correction are encouraging.