Disturbances of mineral metabolism and vascular calcifications in dialysis patients (review)
Malberti, F.; Ravani, P.
Giornale Italiano di Nefrologia Organo Ufficiale Della Societa Italiana di Nefrologia 21(3): 238-244
2004
ISSN/ISBN: 0393-5590 PMID: 15285002 Document Number: 574397
Vascular calcifications are more frequent in dialysis patients than in the general population or in patients with cardiovascular disease and normal renal function. The reasons for this high incidence are multiple. They include traditional factors such as hypertension, diabetes, dyslipidaemia, and specific factors such as sodium overload, hyperomocysteinaemia, chronic inflammation, oxidative stress as well as disturbance of mineral metabolism. Specifically, hyperphosphataemia and the elevated calcium (Ca) x phosphate product have been associated with an increased risk for development of vascular calcification and death. Even though a causal relationship between the use of Ca- containing phosphate binders and the development of vascular calcifications has not been documented, treatment with Ca salts can induce hypercalcaemia, increased Ca x phosphate product, and Ca overload. A net intestinal Ca absorption of 180-500 mg has been documented in uraemic patients after a meal containing 1200 mg of Ca. Thus, treatment with Ca salts may induce Ca overload when a patient is dialyszed against a high dialysate Ca (> 1.5 mmol/L) solution, which is known to determine a positive dialysis balance. On the contrary, an overall negative Ca balance can result from the use of a low Ca dialysate (1.25 mmol/L) when the patients do not receive Ca supplements or vitamin D metabolites. Maintaining a normal Ca and phosphate balance remains one of the primary goals in the management of dialysis patients. Control of hyperphopshataemia should be obtained using either Ca and aluminium- free phosphate binders, such as sevelamer, or Ca salts, while avoiding a daily oral elemental Ca intake > 1.5 g.