This is a prospective, randomized, single blinded, controlled clinical trial designed to compare the clinical effects of sedation with dexmedetomidine versus propofol in patients undergoing cardiac surgery.

The study will include adult patients of both sexes scheduled for elective cardiac surgery with the use of cardiopulmonary bypass (including coronary artery bypass grafting, valve repair/replacement, and combined).

The patients included in the study will be randomized in 1:1 ratio using computer generated numbers into two groups. The first group of patients, upon arrival to the intensive care unit will be sedated with continuous dexmedetomidine infusion in doses 0.2-0.7 mcg/kg/h. Dexmedetomidine infusion will be discontinued before weaning from mechanical ventilation and extubation. The second group of patients, upon arrival to the intensive care unit will be sedated with continuous propofol infusion in doses 1-2 mg/kg/h. Propofol infusion will also be discontinued before weaning from mechanical ventilation and extubation.

Sedation level will be assessed using Richmond Agitation and Sedation Scale (RASS) every two hours. Postoperative analgesia will be managed according to protocol (opioid analgesics, non-steroid anti-inflammatory drugs, paracetamol), with pain level assessment using visual analog scale (0 - no pain; 10 - unbearable pain).

The following data will be registered: age, sex, body mass index (BMI), hemoglobin, heart rate, and LVEF. Among the postoperative parameters, the following will registered: duration of mechanical ventilation (in hours), extubation time, ICU and hospital length of stay (in days), postoperative hemoglobin, blood product transfusion rates, occurrence of atrial fibrillation and assessment of delirium. Assessment of delirium will be performed using the confusion assessment method for intensive care unit (CAM-ICU) every 12 hours during five postoperative days.

Inclusion Criteria:

• patients undergoing open heart surgery with the use of cardiopulmonary bypass (including coronary artery bypass grafting, valve repair/replacement, and combined)
• left ventricular ejection fraction (LVEF) >40%.

Exclusion Criteria:

• preoperative atrial fibrillation
• previous history of interventionally treated arrhythmias
• second and third degree atrioventricular block
• bradycardia with heart rate ≤50/min
• pacemaker
• renal or hepatic insufficiency
• emergency procedures
• history of serious mental illness, delirium, and severe dementia