Acid production and base balance in patients on chronic haemodialysis

Abstract

Acid generation and elimination processes were compared with total base (bicarbonate plus metabolizable anions) turnover in 18 anuric patients undergoing post-dilutional haemofiltration. The study was conducted during the second haemodialysis session of the week by means of a whole-body base balance technique. The results showed that the mean rates of base loss and base gain during dialysis did not differ (i.e. the dialysis base balance approximated to zero). The concurrent mean rate of intestinal base absorption was 66+/-26 mmol/2 days, as calculated from the whole-body balance of the various inorganic cation and anion differences in a metabolic steady state. This level of intestinal base absorption would be capable of neutralizing the 59+/-21 mmol of H(+) ions/2 days that is contributed by sulphuric acid, which is the most important endogenous acid produced in anuric patients. In spite of the fact that intestinal base supply was adequate to neutralize endogenous acid production completely, our patients presented with pre-dialysis non-carbonic acidosis. The depression of plasma bicarbonate levels could not, however, be explained by increased concentrations of the anion gap and organic acids, which were within normal limits both before and after dialysis. We suggest as an alternative hypothesis that this pre-dialysis acidosis may represent an isotonic dilution acidosis that is induced by the ingestion of base-free tap water in order for plasma tonicity to be protected from the accumulation of impermeant dietary solutes, which takes place during the interdialysis period in anuric patients.

Bicarbonate Balance and Prescription in ESRD

“…30,34,37,38 Interdialytic weight gain lowers the bicarbonate level by expanding the bicarbonate space. 34,[42][43][44] Serum bicarbonate is approximately 1 mEq/L lower after the long interdialytic interval than the short interval. 29,45,46 Medication use is important as well; sevelamer hydrochloride reduces serum bicarbonate, whereas phosphate binders containing alkali precursors do the opposite.…”

Relation of Interdialytic Water Retention with Apparent Bicarbonate Space, HCO3-, and pH in Hemodialyzed Uremic Patients

“…In some reports, it is referred that in patients dialyzed three times per week for 4 hours with a blood flow 250 mL/min, dialysate flow 500 mL/min, and IWR 2 less than L. Serum, the prehemodialysis blood, HCO 3 À are approximately 20 mEq/L, serum HCO 3 À value pre-HD less than 17 mEq/L is a serious factor for the development of renal failure osteodystrophy (bone disease). In some reports, it is referred that in patients dialyzed three times per week for 4 hours with a blood flow 250 mL/min, dialysate flow 500 mL/min, and IWR 2 less than L. Serum, the prehemodialysis blood, HCO 3 À are approximately 20 mEq/L, serum HCO 3 À value pre-HD less than 17 mEq/L is a serious factor for the development of renal failure osteodystrophy (bone disease).…”