Calcium and phosphate control by dialysis treatments

Calcium and phosphate changes, besides their involvement in bone disease, have been claimed to also be involved in the increased vascular morbidity and mortality of dialysis patients. Even after the recent advances of therapeutic options, their control still remains a challenging problem. Dialysis treatment is a basic approach to the control of these two electrolytes. Calcium control by dialysis is mainly dependent on its mass balance, which is variably influenced by the calcium concentration difference between blood and dialysis solutions (either dialysate or infusion fluids) and by the duration of the treatment. There is no full agreement on the ideal calcium concentration in dialysis fluids, since this choice is also mostly influenced by the concomitant medical therapy. However, there is some consensus in suggesting a lower calcium concentration in standard hemodialysis (HD) treatment (1.25-1.50 mmol/l) than in dialysis treatments characterized by high convective transport. In peritoneal dialysis, calcium balance is affected by its blood dialysate concentration difference and dialysate glucose concentration, with ideal calcium concentration probably being >1.25 and <1.75 (which are the most commonly used concentrations). Phosphate dialysis balance is also a critical and challenging problem, since the possibility to reach an always desired null or possibly negative balance relies on this. Even though some increased phosphate removal can be obtained with the highest efficiency techniques, such as hemodiafiltration as compared with traditional HD, the most impacting factor still remains the duration of dialysis treatment. However, some experimental attempts at increasing phosphate removal independently of increasing dialysis duration are mentioned.