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_bic) 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_bic 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_bic of 35 mmol/L; B) D_bic of 35 mmol/L then 30 mmol/L; and C) D_bic of 30 mmol/L then 35 mmol/L (change of D_bic 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_bic concentration profile. Blood bicarbonate concentration (blood [HCO₃]) during Treatment C was lower only during the first three HD hours than in Treatment A. Overall blood [HCO₃] was reduced during Treatment B in comparison to Treatment A at each time points. We conclude that a single change D_bic in the middle of HD can alter the rate of change in blood [HCO₃] and pH during HD; time-dependent D_bic had no influence on uremic solute kinetics.