Preliminary technical and clinical evaluation of a new hollow fiber dialyzer with a 5 microns thick cuprophan membrane.

In vitro and in vivo studies were performed on 10 dialyzers with 5 microns thick cuprophan membrane to evaluate hydraulic properties and permeability to solutes. Inlet and outlet pressures of the filter were measured at different blood flows to assess the resistance of the device and the end-to-end pressure drop. Hysolated ultrafiltration was performed to evaluate the spontaneous filtration at increasing blood flows, the ultrafiltration rate at different transmembrane pressures and, finally, the sieving coefficients for solutes. Standard hemodialysis was also performed to study the clearances throughout a 4-h session. During hysolated ultrafiltration the UF rate was increased up to 37 ml/min showing a very high hydraulic permeability of the membrane. The spontaneous filtration rates related to blood flow were quite low. Since the end-to-end pressure drop in the filter was also relatively low at high blood flow we may conclude that the geometry of the device is able to dissociate the influence of blood flow on the hydrostatic pressure inside the filter. This results in a easy modulation of the membrane permeability to water. Sievings were surprisingly high and clearances were stable along the dialysis session (BUN = 196 ml/min, creatinine = 161 ml/min and phosphate = 163 ml/min).