Pre and interdialytic acid-base balance in hemodialysis patients

In an observational study, nine hemodialysis patients using 35 mmol/l bicar bonate dialysate were studied over a 44-hour interdialytic interval. Serum bicarbonate was measured at regular intervals at home and the mean time ave raged concentration was 27.0 +/- 1.2 mmol/l. Seven of the nine patients sho wed a slow linear decline in bicarbonate whilst in two patients levels were unchanged. In 8 of 9 patients the average of the post and predialysis bica rbonate accurately predicted the time-averaged (area under the curve) bicar bonate concentration. In addition, pre-dialysis serum bicarbonate was measu red in 46 patients after both a 2 and 3-day interdialytic interval. The ser um bicarbonate was significantly lower after the 3-day interdialytic interv al (3-day, 22.1 +/- 0.6 vs 2-day, 23.0 +/- 0.5 mmol/l, p<0.05). The results from this study emphasize the importance of standardization of bicarbonate measurement in order to avoid spurious acidosis.