Acid-base balance during biofiltration.

Five patients were shifted from acetate dialysis (AD) to biofiltration (BF); their pre-dialytic acid-base balance (ABB) was re-examined for six months before the start of BF. Samples for ABB were drawn at 0', 30', 60', 120' and 180' during three AD and 1, 2 and 3 hours after them (period A). The same procedure was then repeated two months (period B) and 12 months (period C) after the start of BF. From analysis of the data it is concluded that the correction of AD-acidosis is very rapid during the early two months of BF, but the post-BF ABB may be too alkalotic, with risks if respiratory alkalosis is superimposed. After one year of BF, there were fewer pCO2 falls and pH variations; no more post-BF alkalotic rebounds were observed.