Evaluation of the influence of the surface membrane and blood flow in medium «cut-off» (MCO) dialyzers.

Introduction: Recently, a new class of dialyzers, medium cut-off membranes (MCO), designed to improve the permeability, which could provide an efficacy similar to hemodiafiltration, have been incorporated into our therapeutic possibilities. To increase the knowledge about its use, the objective of the study was to evaluate the effect of the surface and blood flow (Qb) on the depurative efficacy in the MCO membranes.

Material And Methods: We included 19 patients in the hemodialysis. Each patient received 6 sessions, in which the membrane surface was varied, from 1.7 to 2.0 m, and/or the Qb (300, 350, 400 or 450mL/min). In each session, different solutes were determined at the beginning and end of dialysis.

Results: The surface change of the dialyzer did not show significant differences in the removal of small or large molecules, without changes in albumin loss. The increase in Qb was accompanied by an increase in clearance of small molecules, without showing differences in the percentage reduction of β-microglobulin, myoglobin, prolactin, α-microglobulin and α-acid glycoprotein, except for some comparison with Qb 450mL/min. There were also no differences in the loss of albumin in the dialysis fluid, less than 2.5 g in all situations.

Conclusion: The increase of the surface area from 1.7 to 2.0 m in the MCO dialyzer has not meant a greater depurative effectiveness. In these dialyzers the increase of Qb does not seem to be as determinant as in hemodiafiltration except for the clearance of small molecules.