Standard versus no post-filter ionized calcium monitoring in regional citrate anticoagulation for continuous renal replacement therapy (NPC trial)

Background Current guidelines recommend monitoring of post-filter ionized calcium (pfCa) when using regional citrate anticoagulation during continuous renal replacement therapy (RCA-CRRT) to determine citrate efficiency for the prevention of filter clotting. However, the reliability of pfCa raises the question of whether routine monitoring is required. Reducing the frequency of pfCa monitoring could potentially reduce costs and workload. Our objective was to test the efficacy and safety of no pfCa monitoring among critically ill patients receiving RCA-CRRT. Methods This study was a non-inferiority randomized controlled trial conducted between January 2021 and October 2021 at King Chulalongkorn Memorial Hospital, Thailand. Critically ill patients who were treated with RCA-CRRT were randomized to receive either standard pfCa monitoring (aiming pfCa level of 0.25-0.35 mmol/L), or no pfCa monitoring, in which a constant rate of citrate infusion was maintained at pre-determined citrate concentrations of 4 mmol/L with blinding of pfCa levels to treating clinicians. The primary outcome was the filter lifespan. Non-inferiority would be demonstrated if the upper limit of the 95% confidence interval (CI) for the difference in filter lifespan between the groups was less than 20 h. Results Fifty patients were randomized to the standard pfCa monitoring group (n = 25) or no pfCa monitoring group (n = 25). The mean filter lifespan was 54 +/- 20 h in the standard pfCa monitoring group and 47 +/- 23 h in the no pfCa monitoring group (absolute difference 7.1 h; 95% CI -5.3, 19.5, P = .25). When restricting the analysis to circuits reaching the maximum duration of circuit lifespan at 72 h and clotted filters, the filter lifespan was 61 +/- 17 h in the standard pfCa group vs 60 +/- 19 h in the no pfCa monitoring group (absolute difference 0.9 h; 95% CI -11.5, 13.4, P = .88). Compared with the no pfCa monitoring group, the standard pfCa monitoring group had a significantly higher mean citrate concentrations (4.43 +/- 0.32 vs 4 mmol/L, P < .001) and a higher rate of severe hypocalcemia (44% vs 20%, P = .13). No statistical differences were found in filter clotting, citrate accumulation, citrate overload and mortality between the two groups. Conclusions Among critically ill patients receiving RCA-CRRT, no pfCa monitoring by maintaining the citrate concentrations of 4 mmol/L is feasible. Larger randomized controlled trials should be conducted to ensure the efficacy, safety and cost-effectiveness of this strategy.