Calcium and Phosphate Control by Dialysis Treatments

Abstract

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.

Phosphate Kinetics in Hemodialysis: Application of Delayed Pseudo One-Compartment Model

“…Even in case of the model with delay, the volume of central phosphate compartment is about 79% of the measured ECW. Estimated using both models average masses of removed phosphate are in agreement with previous reports that describe conventional HD [5,26] . The observed difference between mass calculated directly from the experimental data and mass estimated by mathematical models are due to the averaging and the approximation of phosphate dialyzer clearance.…”

“…600-700 g in a medium-sized man) is in plasma, 14% in cells and 85% in bones [4,5] . Intracellular phosphate is in equilibrium with extracellular phosphate with a ratio of 0.6 [5,6] .…”

The Importance of Adherence in the Treatment of Secondary Hyperparathyroidism

“…These include fibroblast growth factor-23 increase, vitamin D reduction and in the late stages of the disease, calcium (Ca) and phosphorus (P) modifications. SHPT is strongly related to both cardiovascular and bone diseases and contributes to the definition of chronic kidney disease-mineral bone disorder (CKD-MBD) [1]. Despite the importance of a good control of SHPT, in recent years, DOPPS data have described both in the United States and Europe the progressive increase of the mean levels of parathormone (PTH) levels in the dialyzed population.…”

The Control of Hyperphosphatemia in Renal Failure: Between Vascular Calcification and Inflammation

“…In addition to elderly age, male gender, inflammation, mineral metabolism abnormalities and diabetes, new potential factors are emerging which help to better understand the pathogenesis of VC in CKD. In the last decade, both new molecular and cellular mechanisms have been investigated in the pathophysiology of secondary hyperparathyroidism and VC in CKD [3][4][5] . Accordingly, different bone-related proteins are now certified for their capacity of promoting or inhibiting the process of extraskeletal calcification [6,7] .…”