Portable artificial kidney with advantages of hemodialysis, hemofiltration, and hemoperfusion

The FDA (filtration, dialysis, absorption) system developed in the present study operates on the principle of simultaneous filtration of blood and dialysis against its purified filtrate, the filtrate being purified by a multi-adsorption system. The filtration of blood is done using a hemofilter which permits clearance of solutes up to 50,000 daltons and easy removal of excess fluid overload under minimal osmotic imbalance conditions. The clearance of small solutes in the above pure-convective filtration process is enhanced by returning the purified filtrate to the hemofilter which introduces an additional diffusive mass transport to the otherwise pure-convective process. The purification of the filtrate is done by 3 kg charcoal and 450 gm of cation exchanger in the Ca++ and Na+ form. Sufficient urea binding is achieved by raising the post-treatment urea level from 50 mg% to 150 mg% which may be justified as the blood urea level below 300 mg% was found to be nontoxic by others. By this procedure, about 40 gm urea is removed per treatment by 3 kg charcoal and 3 to 4 liters of excess fluid discarded. Three kg of charcoal is found to bind an adequate amount of phosphate, thus eliminating the use of phosphate binders, such as alumina, which is a toxic material. The ion exchangers in the Ca++ and Na+ form bind an adequate amount of K+ without altering Na+ and Ca++ levels. The filtrate purification cartridge can be easily regenerated and sterilized, if necessary, thus making it inexpensive. A comparison of the FDA system with other systems clearly showed that it has the advantages of HD, HF, and HP while the major disadvantages of HD, HF, and HP are eliminated in the FDA system.