Inclusion Criteria:

1. Age ≥ 45 years
2. Current use of b-blocker therapy>=30 days prior to surgery
3. Undergoing non-cardiac surgery with an expected length of stay ≥ 48 hours for medical reasons
4. Informed consent
5. Undergoing major vascular surgery (excluding carotid endarterectomy, dialysis shunt, and vein stripping) OR

Meet >= 2of the following criteria:

1. Coronary artery disease
2. Congestive heart failure
3. Stroke or transient ischemic attack
4. Diabetes mellitus requiring oral hypoglycemic or insulin therapy
5. Preoperative renal insufficiency (creatinine clearance below 60 mL/min)
6. Peripheral vascular disease, as defined by any of the following: history of ischemic intermittent claudication or rest pain, history of revascularization procedure to legs, peripheral arterial obstruction of >= 50% luminal diameter
7. Age >=70 years
8. Intermediate-risk surgical procedure: intra-peritoneal, intra-thoracic, carotid endarterectomy, major orthopedic (hip, knee, spine) surgery, radical prostatectomy, or head-and-neck surgery

Exclusion criteria: - if meets any of the following

1. Prior adverse reaction to clonidine or a-2 agonists
2. Current use of Clonidine or a-2 agonists
3. Current congestive heart failure
4. Only b-blocker taken by patient is sotalol
5. Left ventricular ejection fraction <=40%
6. Systolic blood pressure < = 90 mmHg
7. Concomitant life-threatening disease likely to limit life expectancy to <=30 days.
8. Clinically significant aortic stenosis, defined as an aortic valve area <=1.0 cm2 and/or peak trans-valvular pressure gradient >= 25 mmHg