The primary aim of the study is to demonstrate that mitochondrial dysfunction occurs in both skeletal muscle and circulating platelets of severely septic and septic shock ICU-admitted patients, as compared to otherwise healthy surgical ones. In order to better clarify the pathogenesis of mitochondrial dysfunction during sepsis, cardiogenic shock patients (suffering from systemic hypoperfusion) will act as additional controls. Markers of oxidative stress will be measured in tissue samples from septic patients. The clinical relevance of mitochondrial dysfunction during sepsis will be assessed in terms of both skeletal muscle and platelet function.