Coagulation inhibitor substitution during sepsis.

This review presents the rationale for and main results of coagulation inhibitor substitution during experimental and human sepsis. Activation of the contact system induces activation of the classical complement pathway with generation of anaphylatoxins, of the kinins pathway and of fibrinolysis. Physiologic inhibition depends on the C1-inhibitor (C1-Inh.). Septic patients exhibit a relative deficiency of biologically active C1-Inh. Substitution with concentrations of C1-Inh has been safely performed and preliminary results are consistent with a possible beneficial effect on hypotension and vasopressor requirement in septic shock. The extrinsic pathway is the main initial coagulation process involved in sepsis-induced DIC. Endothelial and monocyte generation of tissue factor (TF) is activated by bacterial products and endotoxin. Activation of TF is counteracted by a specific tissue factor pathway inhibitor (TFPI). The potential for TFPI substitution to inhibit the activation of the coagulation cascade in sepsis requires further study. Thrombin generation is inhibited by antithrombin III (AT III) and the protein C-protein S system. During sepsis, AT III is consumed and degraded by elastase. Animal studies have shown that DIC and death were prevented by high doses of AT III concentrates. Although a significant reduction in the duration of biological symptoms of DIC has been reported in most human studies, the usefulness of AT III substitution in human sepsis is still debated. None of the studies was able to document a statistically significant reduction in mortality. Protein C is activated by thrombomodulin and, with its cofactor protein S, inhibits factors Va and VIIIa. The free level of protein S depends on the level of the C4b binding protein (C4bBP), an acute-phase complement regulatory protein. During sepsis, protein C activity is significantly reduced, either by acute consumption or by thrombomodulin down-regulation, and increased levels of plasma C4bBP inhibit protein S. Infusion of activated protein C and protein S substitution both protect animals from the lethal effects of bacteria. Combining these different coagulation inhibitors should be carefully studied before its use in septic patients is recommended.