Continuous Antithrombin III Infusion in a Clinically Relevant Sepsis Model

Background: Despite unacceptably high mortality and economic burden, effective therapeutic strategies for sepsis remain elusive. Discrepancies between drug responses in septic patients and animal models may be caused by differences in drug pharmacokinetics and timing of drug administration. Antithrombin III (AT) is an anticoagulant that might ameliorate sepsis-induced multiple organ dysfunction. Clinical trials using bolus AT infusions are conflicting. AT has a short half-life in mice, so we devised a method to continuously infuse drugs starting 6-12 h after cecal ligation and puncture (CLP) surgery (the time needed for clinical diagnosis of sepsis). We asked, “Is AT effective in our clinically relevant sepsis model?” Methods: We catheterized mouse jugular veins, then connected catheters to osmotic minipumps containing saline. After 1-week stabilization, we performed CLP surgery and replaced each minipump with one containing AT or saline. We set a 6-12-h time delay between sepsis induction and treatment by incorporating a 4 cm saline-filled catheter in the circuit and validated the delay by using FITC-sinistrin. Infusion continued for 7 days. Survival studies were conducted. In separate experiments, we collected blood, kidney, liver, and lung at 48 h for biochemical, histological, and microbiological analyses. To examine effect of administration route, we also compared continuous AT infusion with a conventional bolus AT injection. Results: First, continuous AT infusion significantly improved 7-day survival compared to saline-infusion (65% vs. 29%, p = 0.018). Additionally, continuous AT infusion markedly increased survival vs. a single injection of AT (65% vs. 19%, p = 0.003). Continuous AT attenuated liver injury but not renal and lung injury. Furthermore, vascular leakage and inflammatory cytokine were suppressed only in the liver. Focusing on liver in CLP sepsis, we detected the highest accumulation of bacteria and thrombin production, the target of AT, in the liver at 48 h after CLP. Conclusion: In summary, continuous AT infusion improved 7-day survival after abdominal sepsis. Continuous AT infusion attenuated vascular leakage, inflammation, and organ injury in the liver in late phase of CLP sepsis. Liver may be a critical site of intervention because bacteria accumulate there and induce thrombin generation.