Traditional agents such benzodiazepines and propofol have long been used to sedate critically ill patients. Unfortunately, these agents have serious disadvantages that may have a negative impact on patient outcomes. These disadvantages include respiratory depression, prolonged mechanical ventilation, paradoxical agitation, myocardial depression, hypotension, tachyphylaxis, physical dependence, and an unpredictable duration of action following long term infusions. Additionally, concomitant use of an opioid or other analgesic is often required for ICU patients to achieve adequate levels of pain relief, which may also prolong awakening and possibly increase respiratory depression.