Antithrombin activity and central venous catheter-associated thrombosis in critically ill children at high risk of bleeding

Background: Normalization of antithrombin activity may prevent catheter -associated thrombosis in critically ill children at high risk of bleeding. Objectives: To characterize the temporal pattern of antithrombin activity, assess its association with catheter -associated thrombosis and clinically relevant bleeding, and evaluate its relationship with thrombin generation in these children. Methods: In this prospective cohort study, critically ill children <18 years old at high risk of bleeding with central venous catheter were eligible. Antithrombin activity and thrombin generation were measured from platelet -poor plasma and after in vitro antithrombin supplementation. Systematic surveillance ultrasound was performed to diagnose thrombosis. Children were followed for bleeding. Results: We enrolled 8 infants (median age: 0.2 years, IQR: 0.2, 0.3 years) and 72 older children (median age: 14.3 years, IQR: 9.1, 16.1 years). Mean antithrombin on the day of catheter insertion was 64 IU/dL (SD: 32 IU/dL) in infants and 83 IU/dL (SD: 35 IU/dL) in older children. Antithrombin normalized by the day of catheter removal. Thrombosis developed in 27 children, while 31 children bled. Thrombosis (regression coefficient: 0.008, 95% CI: -0.01, 0.03) and bleeding (regression coefficient: -0.0007, 95% CI: -0.02, 0.02) were not associated with antithrombin. Antithrombin was not correlated with in vivo change in endogenous thrombin potential (correlation coefficient: -0.07, 95% CI: -0.21, 0.08). In vitro supplementation reduced endogenous thrombin potential (correlation coefficient: -0.78; 95% CI: -0.95, -0.23). Conclusion: These findings may not support normalization of antithrombin activity to prevent catheter -associated thrombosis in critically ill children at high risk of bleeding.