Antithrombotic Agents in the Management of Sepsis

Sepsis, a systemic inflammatory syndrome, is a response to infection and when associated with multiple organ dysfunction is termed, severe sepsis. It remains a leading cause of mortality in the critically ill. The response to the invading bacteria may be considered as a balance between proinflammatory and antiinflammatory reaction. While an inadequate proinflammatory reaction and a strong antiinflammatory response could lead to overwhelming infection and death of the patient, a strong and uncontrolled proinflammatory response, manifested by the release of proinflammatory mediators may lead to microvascular thrombosis and multiple organ failure. Endotoxin triggers sepsis by releasing various mediators including tumor necrosis factor-alpha and interleukin-1(IL-1). These cytokines activate the complement and coagulation systems, release adhesion molecules, prostaglandins, leukotrienes, reactive oxygen species and nitric oxide (NO). Other mediators involved in the sepsis syndrome include IL-1, IL-6 and IL-8; arachidonic acid metabolites; platelet activating factor (PAF); histamine; bradykinin; angiotensin; complement components and vasoactive intestinal peptide. These proinflammatory responses are counteracted by IL-10. Most of the trials targeting the different mediators of proinflammatory response have failed due a lack of correct definition of sepsis. Understanding the exact pathophysiology of the disease will enable better treatment options. Targeting the coagulation system with various anticoagulant agents including antithrombin, activated protein C (APC), tissue factor pathway inhibitor (TFPI) is a rational approach. Many clinical trials have been conducted to evaluate these agents in severe sepsis. While trials on antithrombin and TFPI were not so successful, the double-blind, placebo-controlled, phase III trial of recombinant human activated protein C worldwide evaluation in severe sepsis (PROWESS) was successful, significantly decreasing mortality when compared to the placebo group. Better understanding of the pathophysiologic mechanism of severe sepsis will provide better treatment options. Combination antithrombotic therapy may provide a multipronged approach for the treatment of severe sepsis.