Does low-calcium dialysate accelerate secondary hyperparathyroidism in continuous ambulatory peritoneal dialysis patients?

A lower-calcium dialysate has been advocated for continuous ambulatory peritoneal dialysis (CAPD) patients for the purpose of increasing oral calcium intake as a phosphate binder and decreasing the need for aluminum-containing phosphate binders and, hence, decreasing the risk of aluminum intoxication. Twelve CAPD patients were evaluated retrospectively after switching from a dialysate containing 3.5 mEq/L of calcium to a new dialysate containing 2.5 mEq/L of calcium. Patients were on the new dialysate for at least 1 year. Serum calcium, phosphate, alkaline phosphatase, aluminum, and intact or N-terminal parathyroid hormone (I-PTH, N-PTH) were measured. Calcium, phosphate, and aluminum did not change significantly. Alkaline phosphatase doubled, but was not statistically significant. I-PTH and N-PTH rose from 2.9 +/- 2.24 to 7.4 +/- 7.4 times normal (p < 0.012). Three of 7 patients who had x-ray evaluations before, during, and 1 year after change of dialysate had radiographic progression of bone disease. Three patients required a parathyroidectomy due to the development of severe secondary hyperparathyroidism. In conclusion, the indiscriminate use of dialysate containing 2.5 mEq/L of calcium, in CAPD patients, may place the patients at higher risk for progression of hyperparathyroidism.