Effect of time-dependent dialysate bicarbonate concentrations on acid-base and uremic solute kinetics during hemodialysis treatments.

Recent studies have suggested benefits for time-dependent dialysate bicarbonate concentrations (D) during hemodialysis (HD). In this clinical trial, we compared for the first time in the same HD patients the effects of time-dependent changes with constant D on acid-base and uremic solute kinetics. Blood acid-base and uremic solute concentration were measured in twenty chronic HD patients during 4-h treatments with A) constant D of 35 mmol/L; B) D of 35 mmol/L then 30 mmol/L; and C) D of 30 mmol/L then 35 mmol/L (change of D after two hours during Treatments B and C). Arterial blood samples were obtained predialysis, every hour during HD and one hour after HD, during second and third treatments of the week with each D concentration profile. Blood bicarbonate concentration (blood [HCO]) during Treatment C was lower only during the first three HD hours than in Treatment A. Overall blood [HCO] was reduced during Treatment B in comparison to Treatment A at each time points. We conclude that a single change D in the middle of HD can alter the rate of change in blood [HCO] and pH during HD; time-dependent D had no influence on uremic solute kinetics.