Vascular calcifications as a footprint of increased calcium load and chronic inflammation in uremic patients: a need for a neutral calcium balance during hemodialysis?

Cardiovascular complications caused by an accelerated atherosclerotic disease represent the largest single cause of mortality in chronic renal failure patients. The rapidly developing atherosclerosis of the uremic syndrome appears to be caused by a synergism of different mechanisms, such as malnutrition, oxidative stress and genetic factors. Recent studies provide evidence that chronic inflammation plays an important role in the pathogenesis of cardiovascular diseases. Hyperphosphatemia and an increased calcium-phosphate ion product have also been associated with an increased risk of death. Cardiovascular calcifications secondary to increases in phosphate and calcium load in dialysis patients might exert an important contribution to the excess cardiovascular mortality and morbidity in dialysis patients. Elevated serum levels of plasma C-reactive protein (CRP) are associated with the extent and severity of the atherosclerotic processes as well as with an increased risk of experiencing myocardial infarction and sudden cardiac death in apparently healthy subjects. In patients affected by pre-dialytic renal failure increased levels of CRP and IL-6 were recorded in 25% of our population; CRP and IL-6 were inversely related with renal function. These data suggest the activation - even in the predialytic phase of renal failure - of mechanisms known to contribute to the enhanced cardiovascular morbidity and mortality of the uremic syndrome. In recent years we have investigated the hypothesis that the chronic inflammatory state of the uremic patient could be at least in part due to the dialytic technique. We have shown that the increase of CRP in stable dialysis patients may be due to the stimulation of monocyte/macrophage by backfiltration of dialysate contaminants. During conventional dialysis, a positive calcium balance and a concomitant inflammatory state may act as cofactors in the development of cardiovascular calcifications. We suggest that this hypothesis should be verified by clinical studies. A reevaluation of the ideal calcium levels in the dialysate is warranted: a neutral intradialytic calcium balance is probably more appropriate, although not easily attainable.