It has been reported that volatile anesthetics preconditioning mediates protection of organ via microRNA. We want to study on the effects of isoflurane preconditioning on expression of microRNA and mRNA in the specimens of internal mammary artery and ascending aorta.

1. Sixty patients scheduled for off-pump coronary artery bypass surgery were randomly assigned to isoflurane wash-in/wash-out group(S-I group, n=30)or propofol intravenous anesthesia group(P group, n=30).
2. Anesthesia and monitoring method All patients were monitored according to the American Society of Anesthesia guidelines and received standard general induction of anesthesia.
3. SI group:10min after intubation,begin to isoflurane wash-in/wash-out operation:isoflurane administration was interrupted for at least 10 min,by washout with a high fresh gas flow(10 l/min)to achieve a MAC value below 0.2. Following the interruption,sevoflurane was again washed in with a high fresh gas flow(6 l/min)to achieve 1 MAC end-tidal concentration as soon as possible,and repeated twice periods of 10 minutes.Discontinuation of the halogenated agent for at least 15 minutes during the last wash out time.
4. P Group:propofol infusion 3-5μg/kg/h.
5. When isoflurane inhaled anesthetic,propofol are stopped infusion.If during this interruption the BIS value increased to>50,0.5 mg/kg propofol was administered repeatedly in boluses until the BIS value have returned to<50.

6.1h after isoflurane preconditioning,specimens of internal mammary artery(surplus arterial tissue is obtained from the repair internal mammary artery)and ascending aorta(the stump after ascending aortic punch)will be saved, and before isoflurane preconditioning,1h,3h,5h after isoflurane preconditioning, central venous blood samples will also be drawn.

Inclusion Criteria:

• age >18 years
• written informed consent;
• scheduled procedures;
• planned isolated OPCABG(multiple bypass are allowed; planned combined intervention such as CABG plus valve surgery are not allowed);
• ejection fraction> 50%;
• NYHA class Ⅱ~Ⅲ;
• serum creatinine <150μmol / l;
• preoperative platelet content > 100 × 109 / l;
• preoperative hemoglobin> 120 g / l

Exclusion Criteria:

• pregnancy;
• planned valve surgery or surgery on the aorta;
• left main coronary artery stenosis> 75%;
• echocardiographic examination revealed moderate to severe mitral, tricuspid, or aortic regurgitation or stenosis;
• unstable or ongoing angina;
• recent (< 1 month) or ongoing acute myocardial infarction;
• use of sulfonylurea, theophylline or allopurinol;
• previous unusual response to an anesthetic agent;
• inclusion in other randomised controlled studies in the previous 30 days; (10)any general anesthesia performed in the previous 30 days;
• emergency operation (not scheduled);
• kidney or liver transplant in medical history, liver cirrhosis (Child B or C);
• chronic respiratory disease (such as chronic obstructive pulmonary emphysema)