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A Semi-Automated and Reproducible Biological-Based Method to Quantify Calcium Deposition In Vitro
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A Semi-Automated and Reproducible Biological-Based Method to Quantify Calcium Deposition In Vitro

Published on: June 2, 2022

Effect of high bicarbonate hemodialysis on ionized calcium and risk of metastatic calcification

Barry Kirschbaum1

  • 1Division of Nephrology, Department of Internal Medicine, Virginia Commonwealth University, P.O. Box 980160, Richmond, VA 23298, USA. bkirschb@hsc.vcu.edu

Clinica Chimica Acta; International Journal of Clinical Chemistry
|April 30, 2004
PubMed

Insights

High bicarbonate dialysate in hemodialysis patients did not lower ionized calcium immediately post-dialysis. However, phosphate rebound may increase metastatic calcification risk, rendering predictive formulas unreliable.

Area of Science:

  • Nephrology
  • Clinical Chemistry

Background:

  • Chronic hemodialysis patients often have calcium and phosphate metabolism disturbances, leading to renal osteodystrophy and vascular calcification.
  • Ionized calcium is the active form, but total calcium is typically measured, necessitating predictive formulas for ionized calcium levels.

Purpose of the Study:

  • To evaluate the effect of high bicarbonate dialysate on acid-base parameters, electrolytes, and calcium and phosphate levels in chronic hemodialysis patients.
  • To assess the immediate post-dialysis risk of hydroxyapatite formation and metastatic calcification.

Main Methods:

  • On-site measurement of acid-base parameters, electrolytes, and ionized calcium using the OPTI Critical Care Analyzer with E-Ca cuvettes.
  • Assays for total calcium, phosphate, and albumin were also performed.

Main Results:

  • High bicarbonate dialysate (1.25 or 1.5 mmol/l calcium, 40 mmol/l bicarbonate) increased post-dialysis pH and total CO2.
  • Total and ionized calcium increased significantly only in patients with central venous catheters, not those with fistulas or grafts.
  • Phosphate concentrations decreased in all patients post-dialysis.

Conclusions:

  • Metabolic alkalosis from high bicarbonate dialysate did not decrease immediate post-dialysis ionized calcium or alter hydroxyapatite formation risk.
  • A potential 40% phosphate rebound 2 hours post-dialysis could increase metastatic calcification risk 2.8-fold.
  • Formulas to calculate ionized calcium are not reliable for this patient population.
Abstract

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