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Our Experience with Acetate-Free Biofiltration

High permeability membranes, characterized by excellent purification capability and biocompatibility, are used in various methods of treatment for Chronic Renal Failure (CRF). Their high efficacy is proved by the high purification capability towards medium sized molecules, as well as heavier molecules (obviously for an adequate KT/V ratio). From the various types of high flux depurative treatments, we have chosen for particular cases the Acetate-Free Biofiltration (AFB): this method provides a diffusive-convective process, in the absence of a buffer solution in the dialysate, and a "calibrated" administration, in post-dilution, of a sterile and apyrogenic bicarbonate solution. The following circumstances show particular indications for the use of AFB: a) an unstable blood pressure, b) a marked alteration in the Acid-Base Balance (ABB) and c) an acetate intolerance. The latter causes numerous side effects both cardiovascular (vasodilation and myocardial inhibition (1-6), maybe by means of interleukin-1 (1) and prostaglandine-E2 (4) or by means of intraand extra-cellular changes of potassium kinetics (2), causing both intraand inter-dialytic hypotensive episodes) and metabolic (1) (worsening of uremic dislipemia, risk of lactic acidose and only indirect buffer effect) mostly in diabetic and hepatic patients (5). Finally, when acetate was used, a hypocapnic reaction was evident being responsible for a reduction in the cerebral blood flow and an adrenergic effect, which can cause symptomatic intradialytic hypotensive episodies (4). Ten CRF patients, 4 males and 6 females, presenting the above mentioned criteria, were treated with AFB for a period averaging 24.8 months (ranging from 20 to 28 months), following a treatment with conventional Bicarbonate-Dialysis (BD) for a period of 72.3 months (ranging from 2 to 192 months) and Biofiltration (BF) for 16 months (ranging from 12 to 26 months). These patients all had a reduced Karnowsky Performance Index (KPI). In 4 of these, KPI was less or equal to 50. At the end of the treatment, blood pressure values were progressively stabilized, with clear clinical improvements in "high risk" patients, even in the early AFB sessions. The ABB confirmed, an effective reduction of the metabolic acidosis in accordance with the literature (1, 6-11). In particular, the adequacy of the method used can be seen for a treatment time of three hours, in both acute and chronic determinations. The metabolic parameters confirmed the above; the same could be said for the improvement in the general conditions, in certain cases even better than expected. The most interesting aspects of the use of AFB as an alternative to other common methods of artificial blood purification depend on the following: when and why should AFB be used? Our experience during this period has convinced us that AFB is useful in all cases where there is an acetate intolerance, or however a severe malaise not due to an independent organic disease (5). As proof of this, one can take the fact that the best results, in terms of improvement in the clinical and metabolic conditions, are obtained in those cases where an absolutely unsatisfactory response to the traditional depurative treatment is associated with the impossibility of demonstrating a concomitant organic disease. The answer to the second question is even more difficult. The purification efficacy in terms of improvement in the metabolic parameters is evident as well as the acid-base re-equilibrium. We wish to emphasize, in accordance with the literature (12), that the treatments where acetate is used, especially those where the association acetatebicarbonate is used (BF), seem to give better results in stabilizing the interdialytic conditions, during long-