On the day of surgery, in operating room, routine monitoring including electrocardiogram, peripheral oxygen saturation, non-invasive blood pressure and Bi-spectral (BIS) electrode will be attached and baseline vitals will be recorded. A peripheral intravenous cannula (16 G) and right radial arterial cannula (18 G) will be secured under local anaesthesia.

Pre-operative cardiac Troponin I levels sent.

All patients will be induced with midazolam 0.05 mg/kg, fentanyl 10 μg/kg and Propofol at the rate 2mg/kg. Rocuronium 1-1.2 mg/kg will be given to facilitate tracheal intubation. Mechanical ventilation will be controlled using 50% oxygen with a tidal volume of 6–8 ml/kg. A normal end tidal carbon dioxide pressure (35–45 mmHg) will be adjusted the respiratory frequency at 12–16 breaths/min. Transesophageal echocardiograph and urine output will be monitored.

In the propofol group (group P), anaesthesia will be maintained with propofol 10 mg/kg/h throughout the intraoperative period. In Propofol and dexmedetomidine (group PD), the anaesthesia will be maintained with dexmedetomidine 0.5 mcg/kg bolus over 10 min than 0.4 mcg/kg/min throughout the surgical procedure and propofol at infusion rate of 2–10 mg/kg/h.

In both groups the muscle relaxation will be maintained with Rocuronium 0.1 mg/kg at every 60 minutes and the depth of anaesthesia will be maintained between 40-60.

The cold cardioplegia solution will be prepared by magnesium sulfate 2.5 g, potassium chloride 2 g, and sodium bicarbonate 0.5 g in 500 ml physiologic saline, and administered into the aortic root every 30 min. The CPB procedure and surgical techniques will be under moderate hypothermia (32-34 °C) were standardized. The CPB prime volume, 1000–1500 ml calculated by patient’s weight, containing balanced salt solution, mannitol, and. The perfusion pressure (50–70 mmHg) will be maintained by a continuous non-pulsatile blood-flow rate of 2.0–2.5 l/min/m�’2 during CPB. All patients will be weaned off CPB by the support of epinephrine and norepinephrine. The patients will be withdrawn from the study if the CPB time was less 60 min or over 240 min or repeated CPB will be more than two times.

After completion of surgery the anaesthetic drugs will be discontinued and patients will be shifted to ICU. In the ICU, the vasopressor requirement will be recorded and further blood sample for biochemical marker will be sent at 6 hours, 24 hours and 72 hours.