Survey on the Effect of Transmembrane Pressure on Middle Molecules' Excretion in Bicarbonate Base Hemodialysis

Background and Aims: The transmembrane pressure (TMP) is an important factor in removing the molecules during hemodialysis. In this study we explained the effect of ultrafiltration increase on the clearance of middle molecules in the hemodialysis patients of Kashan.

Methods: This clinical trial is a before-after study that was performed on 40 hemodialyzed individuals in 2008. At the first stage, the participants were dialyzed with ultrafiltration equal to the difference of their present weight and their dry weight and in the 2^nd stage the ultrafiltration was  increased 2 liters and clearance of each solute was mesured in both stages.

Rusults: In the first stage, the amount of reduction in predialysis serum beta 2 microglobulin (beta2M) level was 3.5% (p = 0.05) and in the second stage it was 14.4% (p = 0.001). Excretion of the small molecules (BUN, Cr and P) in the second stage of hemodialysis in comparision with the first stage of dialysis (conventional method) revealed no meaningful change.

In the all previous studies, low flux dialysis membrane had been used in a standard way, and these studies didn't pay attention to ultrafiltration increase but in this research we improved the role of convection in excretion of the middle molecules by ultrafiltration increase through adding TMP. All pores of the low flux membranes are not uniform and unisize. This manufacturing was problem associated with rising hydrostatic pressure through increase TMP help us for removing beta2M with convection.

Conclusions: The results showed that we can increase the amount of excretion of the middle molecules and dialysis capability with increasing the TMP during bicarbonate base hemodialysis through low flux membranes.