The Influence of Dialysate Calcium on Progression of Arterial Stiffness in Peritoneal Dialysis Patients

BACKGROUND: One of the origins of cardiovascular disease in dialysis patients is arterial stiffness. The aim of our study was to assess the relationship between the calcium content of peritoneal dialysis (PD) solution and arterial stiffness. PATIENTS AND METHODS: We enrolled into the study 49 PD patients who had been treated with the same PD solution for the preceding 6 months. The calcium content of the PD solution was 1.25 mmol/L in 34 patients (low-Ca group) and 1.75 mmol/L in 15 patients (high-Ca group). Study patients were followed for 6 months on the same PD prescription. Arterial stiffness was assessed by measurement of augmentation index (AI) and brachial pulse wave velocity (PWV) at baseline and at month 6 (SphygmoCor: Atcor Medical, West Ryde, NSW, Australia). Demographic data were recorded from patient charts. RESULTS: Mean age of the whole group was 51 +/- 11 years, prevalence of diabetes was 14%, duration of PD was 43 +/- 30 months, percentage of women was 45%, and percentage of patients using a cycler was 33%. We observed no differences between groups with regard to those variables or creatinine clearance, residual renal function, Ca, phosphorus, parathormone, C-reactive protein, lipid parameters, and use of phosphate binder with or without Ca content. Mean arterial pressure was higher in the high-Ca group, but the difference was not statistically significant (100 +/- 22 mmHg vs 88 +/- 18 mmHg, p = 0.06). At baseline, AI was significantly higher in the high-Ca group than in the low-Ca group (27% +/- 10% vs 21% +/- 9%, p < 0.05). Measurements of PWV were not different between the groups (8.4 +/- 1.1 m/s vs 8.5 +/- 1.7 m/s). Measurement of arterial stiffness parameters at month 6 revealed that PWV had increased in the high-Ca group (to 9.6 +/- 2.3 m/s from 8.4 +/- 1.1 m/s, p < 0.05), but had not changed in the low-Ca group (to 8.2 +/- 1.9 m/s from 8.5 +/- 1.7 m/s). The AI did not change in either group. CONCLUSIONS: These data suggest that Ca exposure through PD solution plays a role in the progression of arterial stiffness, which may be related to increased vascular calcification.