Acetate-free biofiltration: a viable alternative to bicarbonate dialysis.

Eight patients were studied during four sessions of acetate-free biofiltration (AFBF). AFBF is a new dialysis technique with no base replacement agents in the dialysate and with the addition in postdilution mode of bicarbonate (HCO3) solution directly into the extracorporeal blood circuit. In this study the effects on acid-base balance of different infusions of sodium bicarbonate (NaHCO3) ranging from 751 to 1,002 mEq per session was evaluated. There were significant positive correlations between the HCO3 infused and net HCO3 gained (r = 0.776, p less than 0.0001) and between HCO3 infused and plasma intratreatment HCO3 changes (n = 0.562, p less than 0.001). Stepwise multiple linear regression analysis demonstrated that HCO3 infused and plasma predialysis HCO3 values played the major role in HCO3 balance in AFBF. The best correction of metabolic acidosis was obtained with the infusion of 900-1,000 mEq of HCO3. The use of substitution fluid with 145 mEq/L of Na concentration avoids the risk of a positive intratreatment Na balance.