Little is known about nutritional Parameters that potentially influence the course of intensive-care unit acquired weakness (ICU - AW). The investigators aim to elucidate the nutritional profiles in blood, urine and muscle in respective patients at risk.

Inclusion Criteria:

• Age ≥18 years
• Written informed consent obtained from the patient's legal representative and later from the patients (as soon as possible)
• Individuals diagnosed with severe head trauma or intracerebral hemorrhage ("central nervous system group") or with severe sepsis/ septic shock ("Sepsis group") at any time from ICU admission until day 5 (i.e. day of screening)
• Patient on the ICU for ≥ 5 days ("ICU long stayer")

Exclusion Criteria:

• Language other than German or French
• Institutionalized Individuals (e.g. prisoners, severe pre-existing mental incapacity)
• Patients with known pre-existing neurological or psychiatric disease that will make informed consent likely impossible
• Patients with known pregnancy or known to be lactating will not be included to the investigation. Due to the observational/ diagnostical nature of the study, a pregnancy test will not be performed.
• Patients on extracorporeal membrane oxygenation (ECMO)
• Clinical signs of pre-existing malnutrition (Body mass index <18)
• Pre-existing evidence for history of anorexia or bulimia
• Parenteral nutrition received within last 5 days (for more than 12 hours) or evidence for parental nutrition needed within next 7 days
• Terminal disease (i.e. life expectancy <14 days)
• Patients with active malignancy
• Patients on biologicals interfering with metabolism (e.g. infliximab)
• Patients on chronic steroid medication (i.e. prednisone equivalent dose >10mg/day)
• Patients on neuromuscular blocking agents on a regular basis (i.e. on a repetitive basis within last 48 hours or evidence for need within next 7 days)
• At screening (day 5): prescribed caloric intake substantially higher (i.e. > 150% of caloric need of indirect calorimetry) than indirect calorimetric results (in intubated patients) or i.e. standard-of-care (25 Kcal/kg body weight/day)
• Severe adipositas defined as BMI >40
• Known pre-existing allergy to standard enteral formulae
• Subject previously enrolled to an interventional trial that is not considered standard-of-care (e.g. investigation of new medication/drug or medical devices)

critically ill patients with severe Sepsis/shock ("Sepsis Group") or intracerebral conditions (CNS Group)