Hemodialysis using Carbostar improves calcium homeostasis by correction of metabolic acidosis

Masai Motoyuki, Sakai Takehiko, Uchino Junji, Ishimaru Atsushi, Inomata Fumi, Yoshida Toyohiko

doi:10.4009/jsdt.45.635

It has been reported that hemodialysis using acetate-free bicarbonate dialysate (Carbostar containing 3 mEq/L of calcium, 2 mEq/L of citric acid, and 35 mEq/L of bicarbonate), corrects metabolic acidosis and decreases the plasma calcium concentration when changing from bicarbonate dialysate (containing 3 mEq/L of calcium, 8 mEq/L of acetate, and 30 mEq/L of bicarbonate). We examined the change in blood gas analysis and serum calcium in 18 patients undergoing maintenance hemodialysis (HD) using CP. Plasma bicarbonate increased rapidly from 23.1±2.3 mEq/L at the start of HD to 28.7±1.3 mEq/L 2 hours later, and thereafter increased slowly to 30.0±1.1 mEq/L at the end of HD (about 4 hours later). This suggests that the accumulation of the buffer base occurs during HD. Post-dialysis ionized calcium decreased in patients with a high ionized calcium concentration at predialysis, increased in patients with a low calcium concentration, and had a tendency to converge with 1.15 mmol/L at the end of HD. It has been considered that an increase in total calcium during HD is mainly due to an increase in the complex calcium. Calcium mass balance during dialysis was studied in the same patients using the continuous syringe extraction method in dialysate. Mean calcium mass transfer was -37.5±162.9. The mean calcium mass transfer related to diffusion was 160.6±144.7. The mean calcium mass transfer related to diffusion was inversely correlated with the predialysis plasma total calcium(r=-0.61, p<0.01). The mean calcium mass transfer related to ultrafiltration was -327 to -83.753 (-198.0±67.3). The negative calcium balance mainly depended on ultrafiltration. The patients were classified into low (i-PTH<60 pg/mL), normal (i-PTH 60-180 pg/mL), and high (i-PTH>180 pg/mL) PTH groups based on measurement of the intact PTH during the previous year of treatment with bicarbonate dyalysate (containing 3 mEq/L of calcium, 8 mEq/L of acetate, and 30 mEq/L of bicarbonate). Then, changes of i-PTH and plasma Ca levels were compared between before and after changing the dialysate to CP. In all three groups, the plasma calcium concentration at the end of dialysis decreased after changing the dialysate to CP. Plasma calcium concentrations before dialysis in normal and high PTH groups did not change. The plasma calcium concentration before dialysis in the low PTH group was higher than that in the normal PTH group before changing the dialysate, but it decreased significantly after changing the dialysate to CP. The plasma i-PTH level increased in the normal and low PTH groups. It was considered that the cause of the increase in PTH of the low PTH group depends on the relatively low concentration of plasma calcium during HD and decreased plasma calcium before HD, due to the improvement of calcium regulation which occurred by the correction of metabolic acidosis.

Hemodialysis using Carbostar improves calcium homeostasis by correction of metabolic acidosis

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