Cardiopulmonary bypass (CPB) surgery initiates a systemic inflammatory response induced by extrinsic (e.g. anesthesia, contact activation within the extracorporeal circuit, endotoxemia) and intrinsic (e.g. tissue damage, endothelial cell activation, ischemia-reperfusion injury of myocardium) factors. Monocytes are important players in systemic inflammation and the main producers of pro- and antiinflammatory cytokines. Monocytes activated by the extracorporeal circuit lead to a dysregulation of inflammatory homeostasis, increased levels of proinflammatory plasma mediators such as TNF-a, IL-1β, IL-6 and IL-18 are joined by antiinflammatory cytokines such as IL-10. This strong inflammatory response induces post surgical monocyte immunosuppression which is indicated by an impaired production of ex vivo LPS induced TNF-a production. Also malfunction of the peripheral circulation with increased lactate levels, pronounced fluid accumulation, increased need of vasopressors and cerebral dysfunction are observed. All of these factors may delay weaning from the ventilator, recovery of organ functions and discharge from ICU. Thus measures to decrease the inflammatory process have the potential to improve the perioperative course.