Cardiac surgery with extracorporeal circulation (ECC) yields a deep immune system dysfunction that exposes patients to postoperative infectious complications. Among these, post-operative mediastinitis with Staphylococcus aureus (SA) generates significant morbidity and mortality. Two radically different approaches have been proposed in recent years to reduce the incidence of this complication. A first approach has attempted, without real success, to decrease postoperative immunosuppression. The second, more efficient, consisted of screening and preoperatively treating patients colonized with SA. However, although its incidence has decreased, postoperative mediastinitis remains a terrible nosocomial infection. The authors believe that a thorough analysis of the immunological changes induced by cardiac surgery will initiate active therapeutics to reduce the post-operative immunosuppression phase, thereby decreasing the risk of nosocomial infections. In addition, a study of the interactions between the operated (host) and staphylococcus aureus (pathogenic) immune systems will provide a better understanding of the mechanisms that expose patients to this bacterium.

In particular, changes induced by the ECC will be evaluated on:

• Indoleamine 2,3-dioxygenase activity (IDO)
• Apoptosis of lymphocytes and dendritic cells
• Polymorphonuclear neutrophils (PMNs)
• Myeloid Derived Suppressor Cells (MDSC )

After general anesthesia and arterial catheterization and prior to the start of ECC, blood samples will be taken for flow cytometry studies, for the purification of PMNs and monocytes. The purified PMNs and monocytes will then be used for the measurement of cytokine, phagocytosis and bactericidal production capacities.

The morning following surgery, blood samples will be taken and follow the same process.

Inclusion criteria

• Patients over 18 years of age
• Patients who require cardiac surgery (valvular and / or coronary) with extracorporeal circulation.

Non inclusion criteria

• Chronic respiratory diseases,
• Preoperative left ventricular dysfunction (LVEF <50%),
• Immunosuppression (HIV infection, systemic corticosteroid therapy, history of cancer in the year before surgery),
• Persons subject to legal protection (safeguard of justice, curatorship, guardianship),
• Persons deprived of liberty.

Patients in the aftermath of an ECC for cardiac surgery are investigated to look for the origin of a hypo-reactivity of PMNs and macrophages during exposure to staphylococcus aureus