INFLUENCE OF THE DIALYZER MEMBRANE MATERIAL ON SODIUM-TRANSPORT IN HEMODIALYSIS

Traditionally Gibbs-Donnan coefficients based on the mean charge of pl asma proteins are used as the only correction factor in equations desc ribing sodium transport across the dialyzer membrane. This ignores the possible impact of the membrane material. Correction coefficients (CC ) of the whole dialyzer were measured during in vivo dialysis as a quo tient of dialysate to plasma sodium in an equilibrated state for diffe rent membrane materials used in commercially available dialyzers. Thei r mean value and correlation with total plasma protein content (TPP) w ere evaluated. CC for the six materials evaluated differed both in the intercept and slope of the regression line CC versus TPP: Cuprophan 1 : CC = 1.0253 - 0.00017 x TPP; Hemophan 1: CC = 1.119 - 0.00175 x TPP; Hemophan 2: CC = 1.095 - 0.00111 x TPP; PMMA: CC = 1.0353 - 0.00044 x TPP; SCE:CC = 1.114 - 0.00145 x TPP; and Cuprophan 1:CC = 1.0562 - 0. 00065 x TPP. The observed differences are attributed to the different charge densities of the membrane materials and suggest that for a prec ise description of sodium transport, the role of the membrane material needs to be considered.