Ancillary Effects of Dexmedetomidine Sedation After Cardiac Surgery

• Drug: Dexmedetomidine
  Dexmedetomidine
• Drug: Placebo
  Normal saline administration matching dexmedetomidine rate of infusion
  Other Name: Saline

• Active Comparator: Dexmedetomidine
  Dexmedetomidine infusion, without a bolus dose, (or a comparable volume of placebo) will be initiated before the surgical incision at a rate of 0.1 mcg/kg/hr at the end of bypass, the dose will be increased to 0.2 mcg/kg/hr. Postoperatively patients will continue to receive the study medication at a rate of 0.4mcg/kg/hr. The study medication infusion will be continued for a total of 24 hours from the initial administration time intra-operatively.
  Intervention: Drug: Dexmedetomidine
• Placebo Comparator: Placebo
  normal saline administration matching dexmedetomidine rate of infusion.
  Intervention: Drug: Placebo

Inclusion Criteria:

1. 18-85 years old;
2. Scheduled for cardiac surgery with bypass (CABG, valve, or combined);
3. Able to provide a written informed consent;
4. Hemodynamically stable (heart rate>= 55).

Exclusion Criteria:

1. Sick sinus syndrome or Wolff-Parkinson-White syndrome
2. Atrio-ventricular block
3. Hypersensitivity or known allergy to dexmedetomidine
4. Hepatic disease, e.g. twice the normal level of liver enzymes
5. AF within 1 preoperative month;
6. Permanent pacemaker;
7. Use of amiodarone or dexmedetomidine within the last 30 days;
8. Patients with an ejection fraction under 30% or who had severe heart failure
9. Myocardial infarction in the previ¬ous 7 days;
10. Body mass index =< 40 (BMI= mass (kg) / height (m)2);
11. Those tak¬ing clonidine within last 48 hours.