Removal of vascular calcification inducer phosphate in different dialysis treatment modalities

Abstract

Approximately 8–10% of the adult population in Europe suffers from kidney diseases. Cardiovascular complications are the leading cause of death in chronic kidney disease (CKD) patients, and vascular calcification is prevalent. High serum phosphate (P) level is a trigger of higher prevalence of vascular calcification in CKD patients. Phosphate is removed from the blood of end-stage renal disease (ESRD) patients regularly by extracorporeal renal replacement therapy, called dialysis. This paper aims to evaluate the calcification capability of CKD phosphate levels and compare the removal of phosphate during the different dialysis modalities. Human vascular smooth muscle cells and rat aortic rings were incubated in a medium containing CKD levels of phosphate. Both, calcium content measurements and histochemical staining proofed significantly increased calcification. Ten uremic patients, five males, and five females mean age 59 ± 16 years, were followed during 40 chronic midweek hemodialysis sessions. Four dialysis modalities with different settings were used once for each patient: hemodialysis (HD), high-flux hemodialysis (HF1, HF2) and postdilutional online hemodiafiltration (HDF). Total removed phosphate (TRP) was calculated by using phosphate concentration and the weight of the total spent dialysate collection. Phosphate reduction ratio (RR) was calculated by using patients’ pre- and post-dialysis phosphate concentrations in serum. Patients’ mean pre-dialysis serum phosphate levels were 1.72 ± 0.57 mmol/L, which is higher than in healthy subjects (0.81–1.45 mmol/L). Phosphate serum reduction ratios achieved during HD procedures were significantly lower from the ratios achieved during HDF and HF2 procedures. The mean total removed phosphate (TRP) values for HD were significantly lower than TRP values of other modalities (HF1, HF2, and HDF). Differences in removal values between HF1, HF2, and HDF were not significant. The results are indicating that phosphate levels presented in CKD increase vascular calcification and it is possible to remove phosphate more effectively by adjusting the dialysis treatment parameters.