To test the contribution of bicarbonate (Bi) to hemodynamic stability during hemodialysis (HD), we compared the effects of ultrafiltration dialysis with bicarbonate and with acetate under conditions of high-sodium (141 mEq/liter) and low-sodium (130 mEq/liter) dialysate concentrations in 12 stable HD patients. Group 1 was patients (N=5) who had normal findings on autonomic testing; group 2, patients (N=7) who had abnormal findings on autonomic testing. All patients and staff were unaware of which dialysate was being used. During the high-sodium dialysate studies, changes in mean blood pressure (MBP), cardiac output (CO), and orthostatic tolerance to standing after HD were similar in both groups of patients with both acetate and bicarbonate dialysate. When the studies were repeated under low-sodium dialysate conditions, several differences emerged between acetate and bicarbonate HD. In group 1, the frequency of adverse symptoms upon standing after HD were reduced with bicarbonate (P<0.05). In group 2, bicarbonate HD prevented a significant decrease in orthostatic MBP after HD. These results suggest that bicarbonate affords no greater hemodynamic stability than does acetate if a dialysate sodium of 141 mEq/liter is used. With lower sodium dialysate, bicarbonate appears to provide a modest improvement in decreasing orthostatic symptoms and signs in patients with and without autonomic insufficiency.
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