Optimum calcium concentration of dialysis fluid for maintenance haemodialysis.

To define the minimum and maximum levels for calcium concentration of dialysis fluid a combination of acute and long-term observations was carried outIn acute experiments the external calcium balance during dialysis was dependent on the gradient between plasma ultrafilterable calcium and dialysis fluid calcium concentration. Changes in plasma calcium during dialysis did not correlate with measured external balance.In long-term studies it was found that raising the dialysis fluid calcium concentration from 5.0 to 6.0 mg./ 100 ml. both arrested biochemical and radiological changes of hyperparathyroidism, and, by causing a progressive fall in plasma phosphates, made metastatic calcification less likely. Raising the concentration to 6.5 mg./lOO ml. in an attempt to compensate for negative alimentary calcium balance caused nausea and vomiting in some patients.A concentration of 6.0+/-0.2 mg./100 ml. is recommended.