Short daily hemodialysis versus online hemodiafiltration: which is better?

The suboptimal nature of conventional hemodialysis (HD) has led to a search for novel treatments. Hemodiafiltration is a strategy to increase combined diffusion and convection, and it represents many theoretical improvements. In contrast, daily HD, with its more frequent treatment, better mimics the physiological functioning of a healthy kidney. Previous studies demonstrated improvements in several health parameters with the use of daily HD, including blood pressure, quality of life and reduced anemia. However, no study has directly compared these two modalities. A prospective sequential study with 9 end-stage renal disease patients (functioning as their own controls) was performed. Patients were switched from conventional hemodialysis (2-3 sessions/week) to short daily HD (2 h / session, 4-6 sessions per week) for four weeks; they were then switched to online hemodiafiltration for another four weeks. All pre-dialysis serum calcium, phosphate, hematocrit, ferritin, iPTH and beta-2 microglobulin were measured before and after conversion from conventional HD to SHD and online HDF (ol-HDF). Single session and weekly spKt/V, StdKt/V and eKt/ V values were calculated during each treatment regimen. After switching from conventional HD to SHD or oL-HDF, improvements were detected in pre-dialysis serum phosphate and Ca x P product, especially in the oL-HDF group. There were no changes in hematocrit, serum calcium or iPTH. The reduction in beta-2 microglobulin was similar in conventional HD and SHD, but it decreased significantly more with oL-HDF. Finally, SHD yielded the highest weekly SpKt/V, eKt/V and StdKt/ V values compared to the other two modalities, while the mean single session Kt/V was greatest in the oL-HDF group. oL-HDF has the potential to remove middle molecules and to improve calcium homeostasis in ESRD patients. Short daily dialysis provides better weekly urea clearance (measured by spKt/V, StdKt/V and eKt/V) than conventional HD or oL-HDF. A new mode of treatment that combines both methods to improve both small and middle molecule clearances may be more promising.