Adding heparin to citrate in continuous renal replacement therapy may extend filter lifespan in COVID-related AKI

Background: COVID may predispose patients to thrombosis and lower filter lifespan Association between D-dimer level (DD) and filter clotting in Continuous Renal Replacement Therapy (CRRT) has not been described Methods: All patients who needed CRRT in Hospital das Clinicas (Brazil) during March to May 2020 (COVID related-AKI (COV+), n=37) and August to September 2019 (COVID unrelated-AKI (COV-), n=18) were studied Anticoagulation in CRRT in COV+ was done with citrate 3mmol/L (ACD, n=19), or citrate 4mmol/L plus non-fractioned heparin 10U/Kg/h (ACD/Hep, n=18), while in COV- with citrate 3mmol/L only Data are expressed in median [IQR] We performed Spearman's correlation between DD and time-free of filter clotting (TFC), and Kaplan-Meier curve to study filter survival by anticoagulation method and DD Results: ACD/Hep group presented lower filter clotting in 72h when compared to other groups (ACD/Hep: 35% vs ACD: 100% vs COV-: 80%, p< 0 05) Analyzingfilter clotting per patient-day, ACD/Hep also presented less clotting than ACD group (ACD/Hep: 41% vs ACD: 100%, p< 0 05) In COVID patients, median TFC was 33 5 h [17 0;72 0] (ACD: 29 0 h [13 0;68 5], ACD/Hep: 40 0 h [17 0;62 0], p: NS) Clotting time from obese patients did not differ from non obese patients (obese: 31 0 h [18 5;57 2] vs non-obese: 56 0 h [16 8;72 0], p: ns) Median DD in all COVID patients was 3,519 [1420- 13,883] Patients with DD below median (<3,500) had higher TFC (ACD high DD: 19 0 h [9 00;27 5], ACD/Hep high DD: 34 0 [17 0;62 0], ACD low DD: 57 0 h [27 2;66 8], ACD/Hep low DD: 67 0 h [26 0;72 0];Figure 1) There was statistically significance in correlation between DD and TFC in ACD patients, but not in ACD/Hep group Conclusions: Heparin may extend filter lifespan in CRRT, and this benefit seem to be greater in high DD patients