SERUM IONIZED CALCIUM, PARATHYROID-HORMONE AND PHOSPHATE IN UREMIC PATIENTS DURING AND BETWEEN HEMODIALYSIS

The serum concentrations of actual ionized calcium (at actual pH), adj usted ionized calcium (at pH 7.4), pH, intact parathyroid hormone (PTH ) and phosphate were studied in ten patients during and between two he modialysis sessions using a dialysate containing 1.66 mmol/l of calciu m. Actual ionized calcium and adjusted ionized calcium increased durin g hemodialysis from 1.19 to 1.38 and 1.43 mmol/l, respectively (mean v alues) and returned to predialysis values within five and nine hours p ostdialysis. Serum PTH decreased from 165 ng/l to 55 ng/l (median valu es) during hemodialysis but two-hour postdialysis the level did not di ffer significantly from the predialysis level. Serum phosphate decreas ed from 2.05 mmol/l to 1. 11 mmol/I during hemodialysis, and increased slowly towards the predialysis level. The level of pH increased from 7.40 to 7.47 during hemodialysis and reached predialysis level after n ine hours. In a multivariate analysis including actual and adjusted io nized calcium, pH, phosphate and PTH, only actual or adjusted ionized calcium was associated with the level of PTH. We conclude that the eff ect of dialysate calcium on the levels of ionized calcium and PTH is o f very short duration postdialysis.