Adsorption in hemodialysis

The use of sorbents in different blood purification techniques is reviewed. The sorbents used in these therapies are divided into two groups: (1) Adso rption occurs fundamentally because of the hydrophobic properties of the so rbents. In this group, the sorbents used in different dialysis techniques a re charcoal and nonionic macroporous resins. (2) Adsorption occurs by chemi cal affinity, such as ion exchange resins and chemisorbents. Sorbents were initially used in hemoperfusion, which caused many adverse events; later, w ith the use of coated charcoal, these undesired effects decreased or disapp eared, but the adsorptive properties, water control, and acid-base balance stilt created problems. For these reasons, the use of sorbents in the treat ment of chronic renal failure was almost totally discontinued. Little by li ttle, interest in these substances has reappeared, and at present, they hav e been used in combination with other blood purification techniques such as hemodialysis hemofiltration, peritoneal dialysis, and finally, hemodiafilt ration. Within the various hemodiafiltration techniques, paired filtration dialysis-charcoal is being used to regenerate the ultrafiltrate, which is u sed as the replacement fluid. Charcoal regenerates the ultrafiltrate and tr ansforms it into a physiological solution with a normal electrolyte composi tion, calcium, bicarbonate, and glucose, having eliminated the majority of both middle and large molecule uremic toxins.If regeneration is done proper ly, this replacement fluid is bacteria and endotoxin free. Studies currentl y are underway on the adsorption of different inflammatory substances in th e ultrafiltrate, which could lead to improvement in the biocompatibility of the system.