Adsorption in hemodialysis. The use of sorbents in different are used to eliminate excess of calcium and to avoid hard blood purification techniques is reviewed. The sorbents used water syndrome [2]. In medicine, sorbents have been in these therapies are divided into two groups: (1) Adsorption used to rapidly eliminate both industrial and pharmacooccurs fundamentally because of the hydrophobic properties logical exogenous toxins, as well as some endogenous of the sorbents. In this group, the sorbents used in different toxins such as bilirubin or porphyrines. dialysis techniques are charcoal and nonionic macroporous resins. (2) Adsorption occurs by chemical affinity, such as ion Sorbents can be divided into large categories: (1) those exchange resins and chemisorbents. Sorbents were initially that have hydrophobic properties and therefore adsorb used in hemoperfusion, which caused many adverse events; the molecules dissolved in the solution in contact with the later, with the use of coated charcoal, these undesired effects sorbent, and (2) those that eliminate solutes by chemical decreased or disappeared, but the adsorptive properties, water control, and acid-base balance still created problems. For these affinity [3]. Within the first category, hydrophobic sorreasons, the use of sorbents in the treatment of chronic renal bents, there are two subgroups: charcoal and nonionic failure was almost totally discontinued. Little by little, interest macroporous resin. Charcoal is produced both from bioin these substances has reappeared, and at present, they have logical substances such as coconut shells or peach pits been used in combination with other blood purification techand from nonbiological substances, such as petroleum.niques such as hemodialysis, hemofiltration, peritoneal dialysis, and finally, hemodiafiltration. Within the various hemodiafil-Again, according to the definitions of the "Consensus Conference on Biocompatibility," hemoperfusion is the

Reinfusion of ultrafiltrate through an uncoated charcoal cartridge proved to be a safe, well-tolerated and simple technique. Further potential benefits of regenerated ultrafiltrate may also include the maintenance of acid-base balance with reinfusion of endogenous bicarbonate.

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PFD (Paired Filtration Dialysis) is the only hemodiafiltration (HDF) technique in which the ultrafiltrate (UF) is continuously available not mixed with the dialysate. As with all convective or prevailingly convective techniques, a replacement fluid is necessary in an amount equal to the difference between the UF and the desired weight loss. This replacement fluid (R) must have an adequate electrolytic balance (Na+, Ca++, and buffer), and must be sterile and pyrogen-free. Using an uncoated adsorbent charcoal cartridge, we "regenerated" the UF obtained in PFD, eliminating the small (except for urea, which was later eliminated by diffusion in the dialyzing section of the PFD system) and the medium-to-large molecules (vit B12 and myoglobin in vitro and beta-2-microglobulin (B2m) and (hANP) in vivo), but not the electrolytes and the endogenous bicarbonate, so as to verify its possible use as R. This technique, experimentally performed in 12 patients under HDF treatment with standard PFD, with a total mean UF of 9650 +/- 875 ml and the use of 130 g of uncoated charcoal, produced a solution with the following composition: Na+ 135.4 +/- 2.4 mmol/l, K+ 3.4 +/- 1.23 mmol/l, Ca++ 1.18 +/- 0.14 mmol/l, HCO3- 26.7 +/- 2.3 mmol/l, phosphates 2.88 +/- 0.81 mg/dl, urea 63 +/- 14 mg/dl, creatinine 0.08 +/- 0.02 mg/dl, uric acid 0.05 +/- 0.0 mg/dl, beta-2 microglobulin 0.5 +/- 0.5 mg/l, and hANP 4.15 +/- 5 pg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

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