Harris DCH, Yuill E, Chesher DW
Correcting acidosis in hemodialysis: Effect on phosphate
clearance and calcification risk
J Am Soc Nephrol
(Dec) 6:1607-1612 1995
Dialytic removal of phosphorous is limited by its mobilization from a deep
tissue pool into extracellular fluid during dialysis, therefore falling
quite low intrdialytically and rebounding post-dialysis. A conflicting
literature suggests that acetate-based dialysate or excessive alkalosis each
may limit phosphate removal. Authors assessed dialytic phosphate removal,
dialysis delivery, and indices of risk of metabolic calcification in 9
healthy, well dialyzed (Kt/V=1.4), patients undergoing standard hemodialysis
(1.1-1.3 m2 cellulose acetate dialyzeers, QB=225-250 mL/min), in a
randomized crossover comparison of three regimens: 1) dialysate bicarbonate
adjusted to achieve pre-HD bicarbonate of 18-20 mM, 2) dialysate bicarbonate
of 40 mM, plus po sodium bicarbonate as needed to achieve pre-HD bicarbonate
of 24-26 mM, and 3) dialysate bicarbonate modeled from 28 to 40 mM during
dialysis plus po supplementation as needed.
There were no differences in phosphate clearance, mass transfer, serum
concentrations of phosphorous, tribasic phosphate, or calcium at any time
among the three treatments. Bicarbonate was lower, as was pH in the first
(standard bicarbonate) treatment. More po bicarbonate supplementation was
required in the modeled vs. high bicarbonate treatment. There was no
adverse effects of bicarbonate supplementation, including no changes in
interdialytic weight gain.
The authors concluded that, as long as calcium and phosphorous were well
controlled, there were no significant effects of standard, high and modeled
dialysate bicarbonate on dialysis delivery, ultrafiltration, phosphate
removal, hemodynamics or risk of metastatic calcification. Interpretation
is limited by the excellent phosphate control in all subjects studied and
the lack of in vivo validation of their index of calcification risk.
Bicarbonate modeling does not appear justified based on claims of improved
phosphate removal or acid-base control.
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