Clinical and biological profiles associated with the time of occurrence of citrate accumulation in patients receiving continuous renal replacement therapy

BACKGROUND: Citrate accumulation (CA) is a feared complication in critically ill patients undergoing regional citrate anticoagulation (RCA) for continuous renal replacement therapy (CRRT). This study aimed to describe the characteristics of patients presenting CA within a large cohort of unselected critically ill patients receiving RCA-CRRT depending on the time of occurrence of CA after CRRT initiation. METHODS: This retrospective, multicenter observational study performed in nine intensive care units (ICU) in Lyon, France, included patients treated with RCA-CRRT between January 2020 and January 2022. CA was defined by a total to ionized calcium ratio (tCa/iCa) ≥ 2.3 associated with hypocalcemia and metabolic acidosis. RESULTS: Among 2080 patients, 76 (3.7%) developed CA: 69 (91%) experienced CA within 24 h after CRRT initiation (initial CA) and 7 (9%) after 24 h (late-onset CA). Only lactate levels at CRRT initiation differed between patients with initial CA and those with late-onset CA (10 mmol/l 4.6-16 vs 1.4 mmol/l 1-3.8, p = 0.006 respectively). In the initial CA group, 39 (57%) exhibited signs of CA within 6 h or less (immediate CA) and 30 (43%) showed signs of CA between 6 and 24 h. Over the first 24 h, patients with initial CA presented a marked increase in lactate levels, worsening norepinephrine requirements, persistent elevation of the tCa/iCa ratio, decrease in prothrombin time, and increase in transaminases. Patients with immediate CA showed higher lactate concentration and more severe metabolic acidosis at CRRT initiation compared to patients with early CA whereas other markers did not differ significantly between the two groups. The area under the Receiver Operating Characteristic curve of lactate and pH for predicting immediate citrate accumulation were 0.75 0.62 - 0.87 and 0.74 0.62 - 0.85 respectively, with optimal cutoff values of 10.6 mmol/L and 7.14 respectively. The ICU mortality rate among patients with CA was 97% compared to 55% in the whole cohort. CONCLUSIONS: CA is a rare phenomenon in patients under RCA-CRRT. Severe metabolic acidosis with hyperlactatemia at CRRT initiation is the most relevant marker to identify patients at risk of immediate CA and should encourage close monitoring of tCa/iCa ratio.