Dexmedetomidine Use in ICU Sedation and Postoperative Recovery in Elderly Patients and Post-cardiac Surgery

Increasing numbers of elderly patients are undergoing cardiac surgery. Elderly patients may have prolonged recovery following cardiac surgery when compared to other groups of patients, and are at higher risk of postoperative delirium, postoperative neurocognitive decline and reduced quality of life following hospital discharge. The goals of sedation and analgesia for patients following cardiac surgery are multifold and include postoperative pain relief, the facilitation of ventilation, resolution of hypothermia and normalization of electrolyte balances. The choice of sedative agent however can impact postoperative outcomes. Dexmedetomidine has been associated with improved quality of recovery in patients undergoing major spine surgery and with a reduced incidence of delirium, both of which can impact a patient's quality of life following surgery. The investigators hypothesized that the use of dexmedetomidine as a sedative agent immediately following cardiac surgery in elderly patients would result in improved quality of recovery and a reduced incidence of delirium in the postoperative period, when compared to propofol. The investigators were also interested as to whether there was an associated improvement in neurocognitive outcomes in this population. Questions: * Does the use of dexmedetomidine as a sedative agent in ICU in elderly patients following cardiac surgery result in improved Quality of Recovery scores when compared with propofol? * Does the use of dexmedetomidine as a sedative agent in ICU in elderly patients following CABG+/- AVR result in a reduced incidence of postoperative delirium as compared to propofol? * Do these patients subsequently have a reduction in cognitive decline?