Table 3.

The effect of different concentrations of dialysate bicarbonate on dialysate composition and diffusion gradients

n = 10 (HDF)	26_DHCO3	32_DHCO3	Pa
Dialysate tCa (mmol/L)	1.36 ± 0.07	1.30 ± 0.04	0.03
Dialysate iCa (mmol/L)	1.260 ± 0.015	1.164 ± 0.01	<0.001
Plasma iCa pre (mmol/L)	1.178 ± 0.062	1.189 ± 0.054	0.66
Plasma iCa post (mmol/L)	1.253 ± 0.05***	1.150 ± 0.026*	<0.001
Dialysate pH	7.18 ± 0.03	7.26 ± 0.03	<0.001
Dialysate HCO3 (mmol/L)	28 ± 0.6	34.2 ± 1.0	<0.001
Diff(iCa) pre (mmol/L)	0.312 ± 0.062	0.204 ± 0.045	<0.001
Diff(iCa) post (mmol/L)	0.249 ± 0.05***	0.237 ± 0.027*	0.42
Diff(pH) pre	−0.194 ± 0.040	−0.101 ± 0.035	<0.001
Diff(pH) post	−0.210 ± 0.021	−0.196 ± 0.025***	0.18
Diff(HCO3) pre (mmol/L)	7.12 ± 1.51	13.49 ± 1.3	<0.001
Diff(HCO3) post (mmol/L)	6.94 ± 0.82	8.13 ± 0.98***	0.02
ΔDiff(iCa) (mmol/L)	−0.063 ± 0.040	0.033 ± 0.031	<0.001
ΔDiff(pH)	−0.017 ± 0.030	−0.095 ± 0.022	<0.001
ΔDiff(HCO3) (mmol/L)	−0.18 ± 1.62	−5.36 ± 1.58	<0.001

Data are shown as means ± SD.

post, postdialysis; pre, predialysis; Δ, intradialytic change; Diff(iCa), diffusion gradient calculated as the differences between inflow dialysate and predialysis plasma water concentrations for iCa: Diff_iCa = 1.12 × inlet dialyser iCa concentration − plasma water iCa concentration, where 1.12 is the Gibbs–Donnan factor.

^aP-value of unpaired test between groups using dialysate bicarbonate 26 and 32 mmol/L.

*P < 0.05 compared with pre-dialysis plasma concentration (paired test).

***P< 0.001 compared with pre-dialysis plasma concentration (paired test).