Acid-base changes and acetate metabolism during routine and high-efficiency hemodialysis in children

Changes in acid-base status and plasma acetate concentrations were studied in eight children during 11 hemodialysis sessions. During dialysis, the blood bicarbonate concentration fell (20.5 +/- 0.7 to 19.6 +/- 0.8 mEq/liter), the Pco2 fell (33.4 +/- 0.8 to 27.5 +/- 1.4 mm Hg), and the pH rose (7.42 +/- 0.01 to 7.48 +/- 0.02). During the hour after dialysis, the bicarbonate concentration rose to normal (23.4 +/- 0.7 mEq/liter), the PCO2 rose (32.8 +/- 0.8 mm Hg), and the pH remained unchanged. The half-life of plasma acetate, measured after dialysis, was 8.7 min. During five "high-efficiency" dialysis sessions (urea clearance, greater than 3.0 ml/min/kg), blood bicarbonate concentration fell 3.2 mEq/liter, PCO2 fell 8.7 mm Hg, and plasma acetate rose to 7.51 mmoles/liter, whereas during six "routine efficiency" dialysis sessions (urea clearance. 1.5 to 3.0 ml/min/kg), blood bicarbonate rose 1.0 mEq/liter, PCO2 fell 36 mm Hg, and plasma acetate rose to 3.52 mmoles/liter. At 1 hour after the end of dialysis, blood bicarbonate, PCO2, and plasma acetate concentrations were similar in the two groups. Clinical problems occurred more frequently in the high-efficiency group during dialysis although the difference was not significant. The data indicate that (1) dialysis with acetate buffer effectively corrects predialysis metabolic acidosis, (2) although children have a high rate of acetate metabolism, during high-efficiency dialysis this rate is exceeded by the influx of acetate, and acid-base abnormalities occur. These abnormalities are transient but may cause clinical problems.