Sedation is very important in critical care. Critically ill patients are submitted to many stressor factors that have potential to affect longterm outcomes. However, oversedation is associated with increased morbidity, including increased time of mechanical ventilation and ICU stay and longterm psychological complications. Daily interruption of sedation is associated with less time under mechanical ventilation and less posttraumatic stress disorder. Intermittent sedation, when compared with continuous sedation, is also associated with decreased time of mechanical ventilation. The aim of this study is to compare intermittent sedation with daily interruption. Our primary endpoint is free-days of mechanical ventilation in 28 days.

A comparison of intermittent sedation - keeping analgesia with fentanyl and midazolam or propofol as boluses if agitation (SAS 5 or more) after adequate analgesia - and daily interruption of sedation - analgesia with fentanyl and sedation wiht midazolam or propofol continuously with daily interruptions every morning until patients awake and can follow simple commands. Sedation is restarted in half previous dosage if agitation (SAS 5 or more) occur.

Inclusion Criteria:

• Patients under mechanical ventilation with less of 24 hours and a expectative of stay intubated for more than 24 hours

Exclusion Criteria:

• Intubation secondary to a neurological cause
• Pregnant women
• Severe asthma or COPD decompensation
• Palliative care