Inclusion Criteria:  Age more than 18 years, both genders ASA I -IV, who will undergo elective cardiac surgeries (CABG, MVR, AVR), receiving invasive ventilation, at Aga Khan University Hospital.  Exclusion Criteria:  Patients undergoing emergency cardiac surgeries Patients with a history of stroke within 6 weeks Patients with a previous history of delirium Patients with a previous history of psychiatric illness Patients with a history of medications for psychiatric illness Patients undergoing reopen surgeries