Mathematical and clinical investigation of the RP6-rhodial 75 system. Evaluation of high and low middle molecular clearance dialysis.

The clearance for "middle molecules" measured in vitro was considerably higher for a polyacrylonitrile than for a cuprophan membrane, even when the former had been used for patients three times. Using a two pool mathematical model, an adequate correlation was found between the calculated values and those measured during RP6-Rhodial 75 dialysis (RP6). The treatment time needed for dialysis of "middle molecules" with the Gambro 13.5mu in single pass (Gambro S. P.) was four times longer than with RP6. In a long-term clinical study, when RP6 and Gambro S. P. dialysis were compared, no difference in the clinical condition of the patients was found. Clinical condition was not affected by the urea or "middle molecule" levels. The ultrafiltration tolerance was improved during hemodialysis with systems resulting in a low urea clearance.