In vitro simulations of peritoneal dialysis: a systematic approach to demonstrating isonatric contraction with sodium...

Two sodium dextran sulfates (DS) were investigated as possible osmotic agents for use in peritoneal dialysis using an in vitro model. Initial studies with a medium molecular weight DS (Mn = 4.000) showed that sodium clearances were higher than water clearances and that both are linear functions of the concentration of polymer. In another series of studies using a low molecular weight DS (Mn = 5,000), it was found that sodium clearances decrease linearly as sodium chloride (NaCL) is added to the initial dialysate solution with only a slight increase in ultrafiltration. By plotting sodium clearances and water clearances as functions of added NaCl at constant polymer concentration, the point at which sodium clearance and water clearances are equal can be determined and, at that point, isonatric contraction can be demonstrated in the vitro model.