A randomized controlled study on the effects of acetate-free biofiltration on organic anions and acid-base balance in hemodialysis patients.

Metabolic acidosis correction is achieved by the transfer of bicarbonate and other buffer anions in dialysis. The aim of this study was to evaluate changes in the main anions of intermediary metabolism on standard hemodiafiltration (HDF) and on acetate-free biofiltration (AFB). A prospective, in-center, crossover study was carried out with 22 patients on maintenance dialysis. Patients were randomly assigned to start with 12 successive sessions of standard HDF with bicarbonate (34mmol/L) and acetate dialysate (3mmol/L) or 12 successive sessions of AFB without base in the dialysate. Acetate increased significantly during the standard HDF session from 0.078 +/- 0.062mmol/L to 0.156 +/- 0.128mmol/L (P<0.05) and remained unchanged at 0.044 +/- 0.034mmol and 0.055 +/- 0.028mmol/L in AFB modality. Differences in the acetate levels were observed at two hours (P<0.005), at the end (P<0.005) and thirty minutes after the session between HDF and AFB (P<0.05). There were significantly more patients above the normal range in HDF group than AFB group (68.1% vs 4.5% P<0.005) postdialysis and 30 minutes later. Serum lactate and pyruvate concentrations decreased during the sessions without differences between modalities. Citrate decreased only in the AFB group (P<0.05). Acetoacetate and betahydroxybutyrate increased in both modalities, but the highest betahydroxybutyrate values were detected in HDF (P<0.05). The sum of postdialysis unusual measured organic anions (OA) were higher in HDF compared to AFB (P<0.05). AFB achieves an optimal control of acid-base equilibrium through a bicarbonate substitution fluid. It also prevents hyperacetatemia and restores internal homeostasis with less production of intermediary metabolites.