PeriOperative ISchemic Evaluation-2 Trial

Inclusion Criteria: 1. Are undergoing noncardiac surgery; 2. Are ≥ 45 years of age; 3. Are expected to require at least an overnight hospital admission after surgery; AND 4. Fulfill one or more of the following 5 criteria: * History of coronary artery disease * History of peripheral vascular disease * History of stroke * Undergoing major vascular surgery * Any 3 of the following 9 criteria: * undergoing major surgery (i.e. intraperitoneal, intrathoracic, retroperitoneal or major orthopedic surgery * history of congestive heart failure * transient ischemic attack * diabetes and currently taking an oral hypoglycemic agent or insulin * age ≥ 70 years * hypertension * serum creatinine \> 175 µmol/L (\> 2.0 mg/dL) * history of smoking within 2 years of surgery * undergoing urgent/emergent surgery Exclusion Criteria: 1. Consumption of ASA within 72 hours prior to surgery 2. Hypersensitivity or known allergy to ASA or clonidine 3. Systolic blood pressure \< 105 mm Hg 4. Heart rate \< 55 beats per minute in a patient who does not have a permanent pacemaker 5. Second or third degree heart block without a permanent pacemaker 6. Active peptic ulcer disease or gastrointestinal bleeding within previous 6 weeks 7. Intracranial hemorrhage documented by neuro-imaging, in the 6 months prior to randomization. This does not include petechial hemorrhagic transformation of a primary ischemic stroke 8. Subarachnoid hemorrhage or epidural hematoma unless the event occurred more than 6 months prior to randomization and the offending aneurysm or arterial lesion has been repaired 9. Drug-eluting coronary stent in the year prior to randomization 10. Bare-metal coronary stent in the 6 weeks prior to randomization 11. Thienopyridine (e.g., clopidogrel, ticlopidine, prasugrel) or ticagrelor within 72 hours prior to surgery; or intent to restart a thienopyridine or ticagrelor during the first 7 days post-op; or currently taking an alpha-2 agonist, alpha methyldopa, monoamine oxidase inhibitors or reserpine; 12. Planned use - during the first 3 days after surgery - therapeutic dose anticoagulation or a therapeutic subcutaneous or intravenous antithrombotic agent 13. Undergoing intracranial surgery, carotid endarterectomy, or retinal surgery 14. Not consenting to participate in POISE-2 prior to surgery 15. Previously enrolled in POISE-2 Trial