Use of sedatives and analgesics is common in mechanically ventilated patients hospitalized in Intensive Care Unit (ICU). That is called " sedation " and aimed to reduce both pain and anxiety and also to allow an effective and atraumatic mechanical ventilation. However, sedation excess and ventilator support excess, both in duration and intensity, are associated with an excess morbidity. Patients usually are systematically sedated after having been intubated. Then, sedation is stopped first before ventilator support is weaning. Several studies shown that rationalized protocols of sedation and ventilation orderings had a beneficial impact on non surgical patients' outcome. Feasibility of these protocols in surgical patients is still unknown. Moreover, no study has evaluated an optimized paired strategy of sedation-ventilation based on the priority setting of ventilation. This priority setting of ventilation should increase patient's comfort in spite of increasing sedatives and analgesics dosing. An paired sedation-ventilation protocol optimized for both duration and intensity of these treatments could improve surgical patients' outcome in ICU.

Intervention group:

• Continuous use of sedatives and analgesics (commonly called "sedation") will be stopped upon enrolment.
• Ventilator asynchrony in Volume assist Controlled Ventilation (VCV) will be treated by switching to Pressure Support Ventilation (PSV) or adjusting setting of VCV.
• Pain, anxiety and agitation will be treated by priority setting of the mechanical ventilator aimed to deliver the most comfortable ventilator support and secondly by adding analgesics and/or psychoactive drugs without inducing a coma state.- Persistent ventilator asynchrony or persistent agitation will be treated by 6-hours continuous sedation periods.
• Extubation will be performed according to criteria defined by the national consensus on mechanical ventilation weaning, which are based on a daily spontaneous breathing trial in the absence of any sedation.

Control group (standard practices):

• Continuous use of sedatives and analgesics (commonly called "sedation") will be daily stopped according to criteria defined by the national consensus on sedation for ICU patients.- During the period before the interruption of sedation, ventilator asynchrony in VCV will be treated by increasing the depth of sedation and then the dose of opioids.
• During the period before the interruption of sedation, pain, anxiety and agitation will be treated by a priority adjustment of sedation according to the nurse driven protocol recommended by the national consensus on sedation for ICU patients.- During the period after the interruption of sedation, ventilator asynchrony will be treated by switching to the PSV mode. In case of return to VCV, asynchrony will be treated by restart of sedation.
• During the period after the interruption of sedation, pain, anxiety and agitation will be treated as for the intervention group.
• Extubation will be performed according to criteria defined by the national consensus on mechanical ventilation weaning, which are based on a daily spontaneous breathing trial in the absence of any sedation.

Inclusion Criteria:

• Ventilated patient in assist control mode after a surgical procedure expected to be ventilated for 12-hours or more
• At least 1 organ dysfunction according to SOFA score
• Non paralyzed because of neuromuscular blocking agents
• Body temperature > or equal 36°CAge > or equal 18
• Surrogate decision maker's consent

Exclusion Criteria:

• Patients without any surgical procedure (medical patients)
• Continuous mechanical ventilation for 24-hours or longer
• Hospitalisation in ICU for 7-days or longer
• Severe ARDS (Acrasis study criteria, New England J Med 2011)
• Neurological injury
• Active toxicomania
• Reduction or cessation of active treatment
• Patient under tutelage
• Pregnancy
• No French health insurance
• Enrollment in another study on sedation or mechanical ventilation