Acetate metabolism during hemodialysis

We infused acetate into normal human subjects and performed kinetic analysis of the plasma and urine values obtained before, during, and after the infusion. The data were best fitted by a first-order elimination process with a mean metabolic clearance rate of 2.3 L/min. Gotch and Sargent had previously suggested that during dialysis, acetate metabolism was zero order. We performed kinetic modeling of acetate concentrations during dialysis. The data were best fitted to a Michaelis-Menton model (i.e., first-order metabolism at low concentrations and saturated at high concentrations). The mean Km for acetate in the dialysis patients was 8.5 mM and the mean Vmax was 18 mmol/min. Patients with a Vmax less than 7 mmol/min usually had a fall in plasma bicarbonate during dialysis while patients with a Vmax greater than 14 mmol/min usually had a rise in bicarbonate during dialysis. It is concluded that during high-surface-area dialysis, the capacity for acetate metabolism will affect acid-base homeostasis. Kinetic modeling will be useful to define acetate-intolerant patients and may be used to predict patients who will benefit from bicarbonate hemodialysis.