Calcium-free predilution for circuit preservation during CRRT without routine anticoagulation: a retrospective single-center ICU experience

Maintaining circuit patency during continuous renal replacement therapy (CRRT) without heparin or regional citrate anticoagulation (RCA) remains challenging in critically ill adults with bleeding risk or when formal anticoagulation protocols cannot be operationalized. We evaluated a calcium-free predilution strategy for CRRT without dedicated circuit anticoagulation in a real-world intensive care unit. We performed a retrospective single-center observational study of 14 critically ill adults treated with continuous venovenous hemodiafiltration using calcium-free predilution without routine heparin or RCA. Total CRRT-hours, treatment duration, clotting events, and serial acid–base and ionized calcium data were abstracted. The primary descriptive circuit-performance analysis prespecified treatments lasting at least 16 h. The cohort accumulated 525 CRRT-hours. Twelve treatments lasted at least 16 h, with a median CRRT duration of 36 h (IQR 25–57). Three clotting events occurred, corresponding to 0.57 clotting events per 100 CRRT-hours, and 11 of 14 treatments (78.6%) were completed without documented filter clotting. Baseline metabolic derangement was substantial, but serial ionized calcium and acid–base abnormalities were clinically manageable with selective supplementation, and no treatment was discontinued because of uncontrolled hypocalcemia or metabolic toxicity. CRRT using calcium-free predilution was feasible in this small high-risk ICU cohort and achieved acceptable circuit performance despite the absence of formal circuit anticoagulation. This approach should be viewed as a rescue strategy when standard anticoagulation cannot be used or operationalized, not as a replacement for RCA.