Mechanical ventilation (MV) is the most frequently used life-support modality in intensive care units (ICUs). To reduce anxiety, stress and promote tolerance of MV, nurses frequently administer a variety of sedative medications to their patients based on subjective observations.

The investigators hypothesize that patient-controlled sedation, compared to clinician-directed sedation, will decrease sedative exposure while decreasing patient anxiety during the episode of mechanical ventilation.

A study to determine whether critically ill patients, during a substantial portion of their time on mechanical ventilation, can reduce anxiety symptoms better with PCS than their caregivers while reducing over-sedation, duration of mechanical ventilation and length of ICU stay will require hundreds of subjects enrolled on a multi-day protocol. However, patient-controlled sedation has been used in less than 20 patients and only for less than 24 hours. Therefore this study is designed to:

1. Establish the feasibility of subject recruitment and protocol adherence in a randomized pilot trial that compares patient-controlled sedation (PCS) using dexmedetomidine to usual sedation practice in mechanically ventilated patients. Feasibility will be defined by: a) number and proportion of patients or proxies who consent to enrollment, b) proportion of eligible subjects enrolled on Days 1,2,3,4 etc, of mechanical ventilation, c) number of days on protocol, up to five days, that subjects successfully use the PCS device, d) ability of ICU nurses to adjust the pump and adhere to the infusion rates of the PCS protocol.
2. Develop and refine the study protocol including: a) improving the proportion of patient daily assessments actually completed such as anxiety and delirium scales, b) develop a protocol to reliably determine when the subject is not able to self-manage their sedation due to weakness, confusion or severe illness; c) create rules for suspending PCS therapy and d) develop a post-ICU symptom interview.
3. Estimate effect sizes on key variables to inform the design of a future randomized trial to compare: a) sedative exposure, anxiety levels, and delirium occurrence between groups, b) adverse event rates and protocol violations related to the drug, pump or both; and c) duration of mechanical ventilation and ICU stay.

Inclusion Criteria:

• adult intubated patients with respiratory failure expected to require mechanical ventilation for at least an additional 48 hours
• subjects have to have at least a 50% chance of being able to operate the PCS machine (i.e., adequate hand strength and cognition)

Exclusion Criteria:

• aggressive ventilatory support such as positive end expiratory pressure > 15 cm of water, prone ventilation, use of high-frequency oscillator ventilator
• hypotension requiring vasopressors (systolic blood pressure < 85 mmHg), second or third degree heart block or bradycardia (heart rate < 50 beats/min.)
• permanent condition preventing the use of push button device (e.g., paralysis)
• pregnancy or lactation
• acute hepatitis or liver failure
• general anesthesia 24 hours prior
• acute stroke or uncontrolled seizures
• acute MI
• severe cognition or communication problems (e.g., coma as main reason for intubation, deafness without signing literacy, dementia or severe delirium)