Abstract
Background: Large-scale adoption of regional citrate anticoagulation (RCA) is prevented by risks of the technique as practiced traditionally. Safe RCA protocols with automated delivery on customized dialysis systems are needed. Methods: We applied kinetic analysis of solute fluxes during RCA to design a protocol for sustained low-efficiency dialysis (SLED) for critically ill patients. We used a high-flux hemodialyzer, a zero-calcium (Ca) dialysate, a dialysis machine with online clearance and access recirculation monitoring, and a separate optical hematocrit (Hct) sensor. Flow rates were Q<sub>B</sub> = 200 ml/min for blood; Q<sub>D</sub> = 400 ml/min for dialysate, with Na = 140 mmol/l and HCO<sub>3</sub> = 32 mmol/l; Q<sub>citrate</sub> = 400 ml/h of acid citrate dextrose A; ultrafiltration as indicated. The Q<sub>Ca</sub> was infused into the return blood line, adjusted hourly based on online Hct and a <24-hour-old albumin level. Results: Using the SLED-RCA protocol in an anhepatic, ex vivo dialysis system, ionized Ca (iCa) was >1 mmol/l in the blood reservoir and <0.3 mmol/l in the blood circuit after citrate but before Ca infusion (Q<sub>Ca</sub>) with normal electrolyte composition of the blood returning to the reservoir. Clinically, SLED-RCA completely abrogated clotting, without adverse electrolyte effects. The Q<sub>Ca</sub> prediction algorithm maintained normal systemic iCa (0.95–1.4 mmol/l) in all patients. The high citrate extraction on the dialyzer prevented systemic citrate accumulation even in shock liver patients. Safety analysis shows that building a dialysis system for automated SLED-RCA is feasible. Conclusion: Using predictive Q<sub>Ca</sub> dosing and integrating control of the infusion pumps with the dialysis machine, SLED-RCA can be near-automated today to provide a user-friendly and safe system.
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