Efficacy of Dexmedetomidine Versus Clonidine to Control Delirium in Patients Undergoing Coronary Artery Bypass Grafting

After Ethics committee approval, and a written informed consent will be taken from every patient, . Patients with a history of mental illness, severe dementia, delirium or undergoing emergency procedures will be excluded.

Anesthesia management will be standardized to minimize any effect of anesthetic type on neurological outcomes. Premedication with midazolam will be limited to a maximum of 0.05 mg/kg.

Anesthesia will be induced with 12 μg/kg fentanyl, 5-7mg/kg thiopental sodium, and 0.15 mg/kg pancuronium and maintained with 1% to 2.0% isoflurane. The heart rate and blood pressure will be maintained within 20% of the baseline values. Anticoagulation will be achieved with heparin to maintain an activated clotting time above 480 s.The CPB circuit will be primed with 1.8 l lactated Ringer's solution and 50 ml of 20% mannitol. Management of CPB will include systemic temperature drift to 32 C, targeted mean perfusion pressure between 60 and 80 mmHg, and pump flow rates of 2.2 l/min/m2 . Myocardial protection will be achieved with antegrade cold blood cardioplegia. A 32-μ m filter (Avecor Affinity, USA)will be used in the arterial perfusion line. Before separation from CPB, patients will be rewarmed to 36 to 37C. After separation from CPB, heparin will be neutralized with protamine sulfate, 1 mg/100 U heparin, to reach an activated clotting time within 10% of baseline.All patients will be transferred to ICU after surgery. Patients will be randomly allocated to either dexmedetomidine or clonidine (control) groups according to a computer-generated randomization code, with allocation ratio 1:1 .Opaque sealed envelopes will be done according to the randomization schedule and opened by a physician not involved in the study . Upon arrival to ICU, in the dexmedetomidine group, patients will receive an infusion of 0.5-0.7 μg/kg/h then 1.4 μg/kg/h if Richmond assessment sedation score from +1 to +4

+4 Combative ,+3 Very agitated ,+2 Agitated,+1 Restless, 0 Alert and calm, -1 Drowsy , -2 Light sedation, -3 Moderate sedation, -4 Deep sedation, -5 Unarrousable A four millilitres vial of dexmedetomidine ( 100 micrograms per ml)will be drawn up and diluted in 46 ml of normal saline.The infusion of dexmedetomidine will be continued for a maximum period of 24 h. Taking into consideration if the heart rate less than 60 per minute or persistent hypotension reduce infusion rate by 0.2 μg/kg/h.Dexmedetomidine infusion will not be discontinued before extubation. Once the patient will be extubated, wean the infusion by 0.1μg/kg/h till reaching 0.2μg/kg/h. Slow the weaning rate if evidence of withdrawal reactions as agitation or hypertension occur. In clonidine group, the patients will receive 0.5μg/kg then 0.1-0.2 μg/kg/h.

Five ampoules of clonidine(750 μg) was drawn up and diluted in 45ml of normal saline.