Electrodialysis of Blood Using Ion-Exchange Membranes

THE correction of electrolyte imbalance and the removal of retention products of the blood during renal failure is at present achieved by the use of artificial kidneys which permit the diffusion of solutes through a semi-permeable membrane. Several types of apparatus used successfully for hemodialysis include those described by Kolff and Watschinger (1956) and Alwall, Norviit, and Steins (1948). Unfavourable reactions Which sometimes occur during dialysis are changes in the arterial blood pressure, hxmolysis, pyrogenic reactions, leukopaenia, and thrombocytopaenia. The maintenance of blood pressure is hazardous because of the large and variable volume in the extra-corporeal circulation; in the case of the Kolff twin-coil artificial kidney the volume of the blood in both loops is 750 ml. The other reactions are probably caused by the extensive surface area of cellophane tubing in contact with blood. To achieve a satisfactory clearance of solutes this arca must be about 18,000 sq. cm. The use of an electric current to accelerate the diffusion of blood electrolytes across cellophane membranes has been described by Sorrentino (1958). As a current is carried through a solution by charged ions, the rate of movement of ions across a menmbrane is directly proportional to the current passed, and is not determined by the surface area of the membrane. The apparatus to be described was constructed in order to determine what rates of ion-exchange could be safely achieved by electrodialysis. Instead of cellophane membranes, stiff sheets incorporating ion-exchange resiins were used, as in the apparatus described by Anderson and Wylam (1956) for the demineralization of plant extracts. In principle, it consists of a sheet A of resin permeable selectively to anions, and a sheet C permeable to cations (see fig.). The electrolytes in solution