Effect of an optimum dialysis fluid calcium concentration on calcium mass transfer during maintenance hemodialysis

The effect of an optimum dialysis fluid calcium concentration (1.625 mmol/l) on calcium mass transfer from dialysis fluid to patient was assessed in patients on routine hemodialysis. While there was a mean body gain of only 3.0 mmol of calcium during dialysis, a marked variation occurred with losses and gains of body calcium up to 16.4 and 18 mmol respectively. A significant correlation was noted between the mass transfer of calcium and the dialysis fluid calcium concentration (r = 0.834, p less than 0.01) which was found to vary by at least 5%. This variation was due to a manufacturing variation and not due to inaccurate dilution of the dialysis fluid concentrate. These data suggests that such a manufacturing variation may expose maintenance hemodialysis patients to periods of excessive calcium loss or gain and thereby favor renal osteodystrophy or soft tissue calcification. In keeping with published data, the mean measured dialysis fluid calcium concentration (1.61 +/- 0.02 mmol/l) should be satisfactory for most patients and it is recommended that dialysis fluid concentrates be manufactured with closer tolerance limits.