Longitudinal Observations on the Mineral Metabolism of Dialysis Patients at the University Hospital

A retrospective review was performed from November 2011 through June 2012 in 49 stable patients receiving ambulatory hemodialysis at the dialysis unit of the University Hospital in San Juan. Measurements of serum phosphate, serum calcium (corrected to albumin levels), intact parathyroid hormone (PTH), and pulse pressure were obtained at 3-month intervals over the course of a 9-month observation period. These longitudinal observations assessed the efficiency of treatment, with the objective being to determine the nature of and then implement such changes as would improve the patients' outcomes. Thirty-three of the 49 patients appeared to have fairly good control of their PTH levels during the observation period. Sixteen patients had levels over 300 pg/ml, and, using Stata data analysis software, a linear relationship with phosphate levels was obtained (p = 0.021, R2 = 0.1037, adjusted R2 = 0.0855). Pulse pressure (PP) measurements obtained at each observation interval showed the following increases: 69% at 3 months, 65% at 6 months, and 57% at 9 months. Calcium-containing phosphate binders were used in one third of the population and vitamin D analogs in 50%. A trend towards a rise in PP was observed as calcium levels increased over 9.5 mg/dl. It is concluded that those patients experiencing that rise need close supervision to avoid the increasing morbidity and mortality associated with mineral metabolism derangement. Wide PPs were observed in these patients during the 9 months of observation, denoting persistent arterial stiffness suggestive of an increase in calcium balance.