Assessment of temperature will be continuously monitored by esophageal probe (MON-A-THERM, 12Fr, COVIDIEN, Dublin, Ireland) (Teso), ZHF sensor (SpotOn, 3M, St Paul, MN, USA) (TZHF) and, in patients requiring cardiac output monitoring, by femoral arterial catheter (Pulsiocath PICCO, PULSION, Munich, Germany) (Tart). The correct positioning of the esophageal probe will be controlled by chest X-ray. The ZHF temperature sensor (TZHF) will be placed on the forehead as recommend by the manufacturer and connected to the SpotOn monitor. Intra cerebral temperature (Tbrain) will be obtained with an intracranial probe used as calibrator for partial pressure of O2 in brain (PbO2, Licox®Combined Oxygen and Temperature Probe 462 mm device necessary for monitoring severe brain injured patients. The ZHF sensor will be changed every 24 hours according to the manufacturer's directions for use. Temperatures will be recorded automatically at a 5-minutes interval via the patient's monitor with an electronic data acquisition system (Data Collect, Phillips) for a maximum of 5 days.