Citrate plasma levels in patients under regional anticoagulation in continuous venovenous hemofiltration

Background: Different methods of regional anticoagulation using citrate in continuous hemofiltration have been described. To date, only such surrogate parameters as pH, anion gap, total calcium concentration, or total calcium-ionized calcium ratio have been proposed to reflect increased plasma citrate levels and thus risk for side effects. However, none of these parameters has been correlated with plasma citrate levels in critically ill patients. Methods: Sixteen patients were treated with continuous venovenous hernofiltration (CVVH) and citrate anticoagulation for a mean of 13 +/- 9 days. Citrate levels were measured every other day, and correlations were calculated with the mentioned parameters. Results: Steady-state citrate levels on treatment day 3 were 16.39 +/- 15.77 mg/dL (range, 2.63 to 73.49 mg/dL [853 +/- 821 mu mol/L; range, 137 to 3825 mu mol/L]). The highest correlation was found between citrate plasma level and total calcium-ionized calcium ratio (R = 0.85; P < 0.001). pH (R = -0.15) and anion gap (R = 0.36) were not helpful in estimating citrate plasma levels in patients treated with citrate-CVVH. Conclusion: Calculating total calcium-ionized calcium ratio is a simple tool that correlates best with citrate plasma levels. We recommend close monitoring of this parameter in all patients administered high doses of citrate as part of regional anticoagulation protocols.