[Control of calcium and phosphate metabolism and prevention of vascular calcifications in uremic patients]

Abstract

Vascular calcifications are more frequent in dialysis patients than in the general population or in patients with cardiovascular disease (CVD) and normal renal function. The reasons for this high incidence are multiple; they include traditional factors such as hypertension, diabetes, dyslipidemia, and specific factors such as sodium overload, hyperomocysteinemia, chronic inflammation and oxidative stress, as well as mineral metabolism disturbances. Specifically, hyperphosphatemia and the elevated calcium (Ca) x phosphate product have been associated with an increased risk for the development of vascular calcification and death. Treatment with Ca salts can induce hypercalcemia, increased Ca x phosphate product and Ca overload. Sevelamer substitution for Ca salts has been documented to attenuate the progression of coronary artery and aortic calcification. A possible mechanism explaining this observation could be ongoing Ca loading related to oral Ca ingestion. Treatment with Ca salts could induce Ca overload, particularly in patients dialyzed against a high dialysate Ca (>1.5 mmol/L) solution, which is known to determine a positive dialysis balance. Conversely, an overall negative Ca balance can result from low Ca dialysate use (1.25 mmol/L) when the patients do not receive Ca supplements or vitamin D metabolites. Maintaining normal Ca and phosphate balances remains a primary goal in the management of dialysis patients. Control of hyperphopshataemia should be achieved either using Ca and aluminum-free phosphate binders, such as sevelamer, or Ca salts, alone or in combination, provided that a daily oral elemental Ca intake of 1.5 g is not exceeded.