Factors affecting transperitoneal calcium flux in patients undergoing continuous ambulatory peritoneal dialysis

Continuous ambulatory peritoneal dialysis (CAPD) is now accepted widely as effective dialytic method for end stage renal disease. Abnormality of calcium metabolism is the etiology of renal osteodystrophy (ROD), however metabolic changes are yet obscure in patients on CAPD. In this work, we studied factors affecting transperitoneal calcium flux in forty seven patients. All patients (forty two men and five women) aged 25-67 years (average 47 years) were treated by CAPD for 0.2-5.4 years (average 2.2 years). They were medicated calcium carbonate as a phosphate binder and la-hydroxyvitamin D₃(0.25-0.75 /¼g/day). Their serum total calcium level was 9.62± 1.28 mg/dl (mean±SD) and albumin level was 3.94±0.44g/dl (mean±SD). Transperitoneal calcium flux was a significant correlation between ultrafiltration volume (UFV) [PC0.001] and serum total calcium concentration level [P<0.001]. Total calcium concentration of effluent was 135.7± 15.1 mg/bag (mean±SD) and net calcium influx was + 14.8mg/bag. Ionized calcium concentration in effluent showed a highly significant correlation to total calcium concentration [P<0.001]. A calcium ionized ratio {% \ ionized calcium concentration/total calcium concentration x 100) was constant (approx. 73%) regardless of dialysate dextrose concentration or ultrafiltration volume. There was no significant correlation between this ratio and dialysate PH. Furthermore, dialysate non-ionized calcium concentration showed no significant correlation to dialysate albumin concentration. It was suggested that diffusible calcium fraction except ionized calcium concerned with transperitoneal flux. In other words, complexed calcium fraction (diffusible, but not ionized calcium) was an important fraction in regard to transperitoneal calcium flux.