Study to Evaluate Hemodynamic Effect of Different Loading Doses of Precedex in Post-surgical Intensive Care Unit (ICU) Patients

Inclusion Criteria: 1. Subject or the subject's legally authorized representative has voluntarily signed and dated the informed consent document approved by the Research Ethics Board (REB). 2. Initially intubated and mechanically ventilated adult post-operative subjects in an intensive care setting (e.g., post operative care unit, post anesthesia care unit, etc.) that are expected to require sedation for at least 2 hours. 3. Has an American Society of Anesthesiologist (ASA) classification of 1, 2, 3 or 4. ASA Physical Status Classification System * P1 A normal healthy subject * P2 A subject with mild systemic disease * P3 A subject with severe systemic disease * P4 A subject with severe systemic disease that is a constant threat to life * P5 A moribund subject who is not expected to survive without the operation * P6 A declared brain-dead subject whose organs are being removed for donor purposes. 4. If female, subject must be postmenopausal, surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy), or practicing at least one of the following methods of birth control: * hormonal contraceptives (oral, parenteral or transdermal) for at least 3 months prior to study drug administration * intrauterine device (IUD) * double-barrier method (condoms, contraceptive sponge, diaphragm or vaginal ring with spermicidal jellies or cream). Exclusion Criteria: 1. Subjects \<18 years of age. 2. Subjects with a 2nd degree Mobitz Type II or 3rd degree heart block, unless the subject has a permanent pacemaker or pacing wires are in situ. 3. Subjects with a known allergy to dexmedetomidine. 4. Hypotension based on repeat assessments prior to (within 15 minutes) starting study drug defined as Systolic BP \<90 mmHg or Diastolic BP \<60 mmHg. 5. Pre-existing bradycardia prior (within 15 minutes) to starting study drug defined as HR \<50 bpm. 6. Subjects who, in the opinion of the Investigator, have any other condition where the risks of dexmedetomidine would be expected to outweigh its benefits (e.g., cardiogenic shock on \>2 vasopressors, death anticipated within 48 hours).