Pre-operative Intra-nasal Dexmedetomidine or Insulin for Prevention of Early Post-operative Cognitive Dysfunction in Patients Undergoing Elective Coronary Artery Bypass Graft.

3 ml of saline 0.9 % twice daily for 2 days preoperatively at fixed time ( 9 am and 6 pm)

20 IU of regular insulin on 3 ml saline 0.9% twice daily for 2 days preoperative via mucosal atomization device at fixed times ( 9 am, 6 pm)

1.5 mic/kg on 3 ml saline 0.9% twice daily for 2 days preoperative via mucosal atomization device at fixed times ( 9 am, 6 pm)