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Increased total to ionized calcium ratio during continuous venovenous hemodialysis with regional citrate anticoagulation

Meier-Kriesche, Herwig-Ulf MD; Gitomer, Jeremy MD; Finkel, Kevin MD; DuBose, Thomas MD

CLINICAL INVESTIGATIONS
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Background Citrate anticoagulation is commonly used for continuous venovenous hemodialysis (CVVHD) to minimize the risk of bleeding complications. We have previously reported a liver failure patient undergoing citrate-based CVVHD with elevated serum total to ionized calcium ratio. Diminished liver metabolism of citrate with resultant elevated systemic citrate was thought to be the cause.

Methods To determine the incidence and clinical significance of an elevated total to ionized calcium ratio during citrate-based CVVHD, 161 patients undergoing citrate-based CVVHD were screened for the presence of an elevated total to ionized calcium ratio (the subset with increased total to ionized calcium ratio comprised the study group). Because all patients in the study group had liver failure, two control groups of patients with normal total to ionized calcium ratios were formed—those without liver failure (control I) and those with liver failure (control II).

Results An elevated total to ionized calcium ratio was detected in 12% of all patients. Thirty-three percent of liver failure patients demonstrated an elevated total to ionized calcium ratio. The study group demonstrated significantly higher mean total calcium levels, significantly lower mean ionized calcium levels, and significantly higher mean total to ionized calcium ratios than controls. As a result, the study group also had significantly increased mean calcium chloride replacement requirements in comparison with controls. The mean calcium to citrate infusion ratio was elevated in the study group in comparison with controls. An elevated total to ionized calcium ratio was associated with increased mortality in comparison with controls. No patients suffered complications from ionized hypocalcemia or elevated serum total calcium.

Conclusions Systemic citrate accumulation as evidenced by an elevated total to ionized calcium ratio occurs commonly in patients requiring CVVHD using citrate-based regional anticoagulation. Observing changes in the total to ionized calcium ratio can aid in early detection of patients with hepatic failure who are unable to appropriately metabolize citrate and will require calcium chloride infusion rates significantly above normal.

From the Division of Renal Disease and Hypertension, The University of Texas Medical School at Houston, Houston, TX.

Observing changes in the total to ionized calcium ratio can aid in early detection of patients with hepatic failure who are unable to appropriately metabolize citrate and will require calcium infusion rates significantly above normal.

© 2001 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins