Patients who are in the intensive care unit after surgery and require mechanical breathing support (intubation and ventilation) usually require sedation to avoid agitation and excessive stress responses. Short-acting sedatives such as midazolam and propofol are the drugs typically used for this. Propofol provides for fast sedation and fast recovery from sedation. Midazolam is slower to sedation and slower for recovery, but may provide some advantages over propofol, such as a lower incidence of hypotension (low blood pressure). This study will look at propofol compared to a product with fast sedation and recovery like that of propofol but with less of a chance for hypotension like with midazolam. Patients will be treated with the product for up to 8 hours and then will be monitored for 8 hours following treatment.