Coagulation inhibitors in the treatment of sepsis.
Despite advances in supportive care, sepsis and septic shock continue to be major causes of morbidity and mortality in critically ill patients. The lack of efficacy of anti-inflammatory drugs in patients with sepsis has shifted interest toward developing alternative treatments. The observation that clotting system activation may in part underlie the physiological derangements of sepsis has resulted in efforts to target the clotting cascade as a therapeutic strategy. Anticoagulants have been shown to ameliorate physiological derangements and improve survival in animal sepsis models. Three agents have undergone extensive study in humans: recombinant human activated protein C (rhAPC, drotrecogin-alpha), antithrombin III (ATIII) and tissue factor pathway inhibitor (TFPI). While a recent Phase III study of rhAPC suggests a survival benefit in patients with sepsis, major concerns about this trial include the manner in which the study was conducted, the potential toxicity of rhAPC and the questionable efficacy of this agent in patients with low mortality risk. Further clinical testing of rhAPC appears to be necessary to better define the target population most appropriate for its use. In contrast, a large Phase III study of high dose ATIII in patients with sepsis failed to show a treatment benefit with this agent. Finally, while TFPI has undergone extensive preclinical and Phase II testing, the results of Phase III studies have not been published. In summary, while coagulation inhibitors may ultimately have a therapeutic role in selected subgroups of patients with sepsis, the efficacy and safety of this class of agents remain to be proven.