Malnutrition is a major risk factor for morbidity and mortality of patients managed in intensive care unit. Early recognition and treatment of adult malnutrition are recommended in acute care settings especially for patients requiring mechanical ventilation. Biochemical indicators like serum concentrations of albumin and prealbumin (transthyretin) have a tradition of being used as markers of nutritional status but remains influenced by nonnutritional factors. A recent assessment of quadriceps muscle diameter with ultrasound method has gained interest for screening and follow-up of muscle weakness at the bedside in critically ill patients. In this light, the MALICUS project aims to investigate the validity of ultrasound as measurement tool for assessing malnutrition acquired in intensive care unit.

Skeletal muscle is central to cytokine regulation and it contributes 85% of total body glucose clearance. Some research findings suggest that muscle wasting is a smoldering inflammatory state partially driven by cytokines and oxidative stress but these conclusions need to be investigated in context of critically ill patients and perioperative settings.

The investigators search to determine impact of inflammatory biomarkers (IL-1, IL-6 and TNF-α) and oxidative stress (evaluated by quantifying the global anti-oxidative defenses in patient with an original method (Patrol® test) based on the use of excited molecular oxygen (singlet oxygen) as a source of ROS on erosion of lean body mass measure with quadriceps muscle ultrasound. Consequently, in an ancillary study of the MALICUS project, the investigators wish to investigate interaction between acute inflammation and muscle wasting.

Study Population

Subjects will be enrolled from 2 venues:

1. Adults ICU patients (> 18 years) requiring period of mechanical ventilation. Subjects affiliated with an appropriate social security system
2. Adults patients admit requiring ICU length of stay < 48h after eligible surgery

1. MALICUS Study

   Inclusion Criteria:

   - Patient requiring invasive mechanical ventilation

   - Expected duration of ventilation longer than 48 hours

   - Age > 18 years

   • Subjects affiliated with an appropriate social security system

   Non inclusion Criteria:

   - Invasive mechanical ventilation started for more than 48 hours

   - Patient severely malnourished at baseline (at least one of the following criteria)

   • Prealbuminemia < 0,11 g/L

   • BMI ≤ 18,5 (or ≤ 22 beyond 70 years)

   • Unintentional weight loss > 5% in the previous month or > 10% in the last 6 months - Glomerular nephropathy history/nephrotic syndrome, chronic renal failure (MDRD < 30 ml/min), liver cirrhosis or exudative gastro-enteropathy - Glucocorticoid (> 10 mg / day of prednisone equivalent ) long-term therapy ( > 1 month) - Impossible ultrasound measure of anterolateral diameter for the two quadriceps muscles

     - Neuromuscular disease that can cause muscle atrophy at a lower limb, without any support in the ICU

2. Control group - BIOBANK-MALICUS

Inclusion criteria:

• Elective surgery requiring an ICU stay (neurosurgery, vascular surgery, thoracic surgery)
• Expected duration of ventilation shorter than 48 hours

Non inclusion criteria:

• Elective surgery with cardiopulmonary bypass