Microvascular responses to cardiopulmonary bypass.

Cardiopulmonary bypass can result in proinflammatory and procoagulant changes that can contribute to morbidity and mortality in heart surgery patients. These responses, many of which are mediated by activation of endothelial cells, normally serve to repair damaged tissue or as defenses against infection. Once activated in the setting of surgery and trauma, these responses may cause unwarranted tissue destruction if they occur inappropriately or too diffusely. The proinflammatory response results in the release of cytokines and subsequent localization of neutrophils, which can disrupt the endothelial barrier and damage underlying tissue. The procoagulant response is characterized by the transcriptional activation of tissue factor, subsequent thrombin generation with subsequent microvascular thrombosis. Techniques to inhibit endothelial cell activation while attempting to preserve the body's anti-infectious and repair mechanisms are being investigated. These include hypothermia, blockade of adhesion molecules, blocking of chemotactic factors such as interleukin-8, and prevention of transcriptional activation by inhibiting the action of nuclear factor kappa-B, which activates genes involved in this process.