Regional citrate anticoagulation (RCA) for continuous venovenous hemodiafiltration (CVVHDF): initial experience

In the intensive care setting, some patients develop acute renal failure (ARF) as a component of multiple organ failure, and are at high risk for bleeding. The inapropriate control of anticoagulation during CVVHDF may lead to bleeding due to excessive anticoagulation, while circuit clotting decreases dialysis effectiveness, increases blood losses and the need for transfusion. The risk of bleeding may be minimized by using RCA. Citrate reduces ionized calcium (Ca_i²⁺) by chelation. Therefore, we decided to establish RCA in our ICU. A total of 11 patients (APACHE = 25, 18-35) with ARF were treated with CVVHDF. They were on vasoactive drugs and under hemodynamic monitoring and mechanical ventilation. CVVHDF: Q_b 100 ml/min, Q_d 1-2 l/h, minimal UF600 ml/h. RCA protocol (UCLA, San Diego, EUA): 4% trisodium citrate (arterial line), CaCl₂ 1 mEq/10 ml (central venous line), dialysate (Na⁺ 117, K⁺ 4, Cl^- 122.5 and Mg²⁺1.5 mEq/l, without Ca²⁺ and alkali) and postfilter replacement solution (0.9% saline). Goal: post-filter Ca_i²⁺ from 0.25 to 0.35 mmol/l. Citrate and calcium rate infusion changed from 150 to 190 ml/h and from 40 to 90 ml/h, respectively. A total of 1194 h of treatment (110 h/patient) was performed and 21 filters (mean filter life 57 h) were used. Mean initial serum and during treatment Ca_i²⁺ was 1.11 and 1.10 mmol/l, respectively. Ca_i²⁺ postfilter was 0.29 mmol/l. Two severe hypocalcemic (Ca_i⁺² < 0.90 mmol/l), two hypercalcemic (Ca_i⁺² > 1.35 mmol/l) and one hypernatremic (Na⁺ > 150 mEq/L) episodes occurred. Important metabolic alkalosis (HCO₃^- > 30 mEq/l) was present in two situations. There were no bleeding episodes related to RCA. In conclusion, RCA is a feasible treatment in the ICU. However, it demands constant metabolic control (four to six times/day). Postfilter Ca_i²⁺ measurement, instead of activated clotting time (ACT), can be used to guide citrate rate infusion. Filters showed good performance during this study.