Determinants of Calcium Infusion Rate During Continuous Veno-venous Hemofiltration with Regional Citrate Anticoagulation in Critically Ill Patients with Acute Kidney Injury

BACKGROUND: It is unclear that how to decide the calcium infusion rate during continuous veno-venous hemofiltration (CVVH) with regional citrate anticoagulation (RCA). This study aimed to assess the determinants of calcium infusion rate during CVVH with RCA in critically ill patients with acute kidney injury (AKI). METHODS: A total of 18 patients with AKI requiring CVVH were prospectively analyzed. Postdilution CVVH was performed with a fixed blood flow rate of 150 ml/min and a replacement fluid flow rate of 2000 ml/h for each new circuit. The infusion of 4% trisodium citrate was started at a rate of 29.9 mmol/h prefilter and adjusted according to postfilter ionized calcium. The infusion of 10% calcium gluconate was initiated at a rate of 5.5 mmol/h and adjusted according to systemic ionized calcium. The infusion rate of trisodium citrate and calcium gluconate as well as ultrafiltrate flow rate were recorded at 1, 2, 4, 6, 12, and 24 h after starting CVVH, respectively. The calcium loss rate by CVVH was also calculated. RESULTS: Fifty-seven sessions of CVVH were performed in 18 AKI patients. The citrate infusion rate, calcium loss rate by CVVH, and calcium infusion rate were 31.30 (interquartile range: 2.70), 4.60 ± 0.48, and 5.50 ± 0.35 mmol/h, respectively. The calcium infusion rate was significantly higher than that of calcium loss rate by CVVH (P < 0.01). The correlation coefficient between the calcium and citrate infusion rates, and calcium infusion and calcium loss rates by CVVH was −0.031 (P > 0.05) and 0.932 (P < 0.01), respectively. In addition, calcium infusion rate (mmol/h) = 1.77 + 0.8 × (calcium loss rate by CVVH, mmol/h). CONCLUSIONS: The calcium infusion rate correlates significantly with the calcium loss rate by CVVH but not with the citrate infusion rate in a fixed blood flow rate during CVVH with RCA.