Sepsis and complications to sepsis are major causes of mortality in critically ill patients. Rapid treatment of sepsis is of crucial importance for survival of patients. In the ICU, the infectious status of the patient is often difficult to assess because symptoms cannot be expressed (unconscious or sedated patients) and signs may present atypically because of immunologic incompetence and masking by the drugs given and thermo-therapy. Biological and biochemical markers of inflammation (White Blood Cells (WBC), C-reactive protein) may often be influenced by other parameters than infection, such as: trauma, surgery, other types of inflammation such as rheumatoid diseases (C-reactive protein) and gluco-corticosteroid treatment (WBC), and may be unacceptably slowly released after progression of an infection. At the same time, lack of a relevant antimicrobial therapy in an early course of infection may be fatal for the patient.