Bicarbonate hemodialysis: influence on plasma refilling and hemodynamic stability

The present study compares the effect of sodium bicarbonate (LoNaHCO3, Na = 134, HCO3 = 33 mEq/l) and sodium acetate (LoNaAc, Na = 134, acetate 33 mEq/1)dialysate on the extravascular fluid mobilization (VFM) and hemodynamic changes in 6 patients during 3 h of hemodialysis with equivalent fluid ultrafiltration of about 600 ml/h. The cumulative decrease in plasma volume after 1, 2 and 3 h of dialysis was significantly less during LoNaHCO3 dialysis than during LoNaAc dialysis, with plasma volume almost completely refilled by VFM during the first 2 h of LoNaHCO3 dialysis. High sodium acetate dialysate (HiNaAc, Na = 144, acetate = 33 mEq/1) with equivalent fluid ultrafiltration also resulted in less net decrease in plasma volume and greater VFM than LoNaAc, although the temporal pattern of refilling was somewhat different from that during LoNaHCO3: rapid and complete refilling during the early portion of LoNaHCO3, slower and more progressive refilling during HiNaAc, with similar cumulative refilling for LoNaHCO3 and HiNaAc by 3 h. Mean arterial pressure (MAP) tended to decrease during LoNaAc dialysis, whereas MAP remained stable during LoNaHCO3 and increased slightly during HiNaAc. This study, therefore, suggests that improved hemodynamic stability utilizing bicarbonate dialysate may be due, in part, to greater plasma refilling and better preservation of plasma volume.