Critical care : the official journal of the Critical Care Forum
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Thrombin is a multifunctional protein, with procoagulant, inflammatory and anticoagulant effects. Binding of thrombin to thrombomodulin results in activation of Protein C and initiation of the Activated Protein C anticoagulant pathway, a process that is augmented by the endothelial cell Protein C receptor (EPCR). Activated Protein C has demonstrated antithrombotic, anti-inflammatory, and profibrinolytic properties. ⋯ Activated Protein C has also been shown to modulate inflammation. When the level of thrombomodulin or Protein C is reduced in sepsis there is a vicious cycle of coagulation and inflammation, with potentially lethal consequences. In vitro studies and animal models have shown that Activated Protein C blunts the inflammatory and coagulant response to sepsis through a variety of mechanisms.
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Severe sepsis, defined as sepsis associated with acute organ dysfunction, results from a generalized inflammatory and procoagulant host response to infection. Coagulopathy in severe sepsis is commonly associated with multiple organ dysfunction, and often results in death. The molecule that is central to these effects is thrombin, although it may also have anticoagulant and antithrombotic effects through the activation of Protein C and induction of prostacyclin. ⋯ Thrombomodulin on endothelial cells coverts Protein C to Activated Protein C, which has important antithrombotic, profibrinolytic and anti-inflammatory properties. A number of studies have shown that Protein C levels are reduced in patients with severe infection, or even in inflammatory states without infection. Because coagulopathy is associated with high mortality rates, and animal studies have indicated that therapeutic intervention may result in improved outcomes, it was rational to initiate clinical studies.
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Cerebral vasospasm is a poor resulting outcome of a ruptured cerebral aneurysm; to clarify the mechanism of vasospasm it is important to improve this outcome. C-type natriuretic peptide (CNP) is present in the brain as a cerebral vasodilator; it is also an endothelium-derived relaxing factor produced via cGMP. We speculated that CNP might be an inhibitor of cerebral vasospasm after subarachnoid hemorrhage (SAH). ⋯ CNP concentrations in the CSF were high in the acute phase after SAH, whereas plasma CNP concentrations remained constant. However, our findings did not support our hypothesis because we did not find any relationship between vasospasm and changes in CNP concentrations in the CSF.