We are trying to investigate whether intraoperative dexmedetomidine infusion could decrease the incidence of intraoperative hypokalemia and arrhythmia, and myocardial injury in patients undergoing off-pump coronary artery bypass graft, and trying compare these effects with those of remifentanil infusion.

Alpha2-adrenergic agonist, dexmedetomidine, is recently used for sedation, analgesia or adjuvant to general anesthesia. Postsynaptic activation of alpha2 adrenoceptors in the central nervous system (CNS) inhibits sympathetic activity and thus can decrease blood pressure and heart rate. The blockade of sympathetic activity decrease the neuroendocrine stress response and may decrease the incidence of hypokalemia. The hypokalemia can increase the incidence of arrythmia, especially in cardiac patients. We postulated that dexmedetomidine could decrease the neuroendocrine stress response, thus decrease arrhythmia during cardiac surgery. Furthermore, dexmedetomidine have been reported to have cardioprotective effect with previous animal studies.

Therefore, the aim of the present study is to investigate whether the intraoperative dexmedetomidine infusion can reduce the incidence of hypokalemia and arrythmia, and myocardial injury in subjects undergoing off-pump coronary artery bypass graft. We are also trying to compare these effects with those of remifentanil infusion.

Inclusion Criteria:

• Those undergoing off-pump coronary artery bypass graft during March, 2012 ~ February, 2013 in Samsung Medical Center
• Age between 20 and 70 yrs old

Exclusion Criteria:

• Any patients with plasma aldosterone, or glucocorticoid disorder including primary hyperaldosteronism, renovascular hypertension, rennin-secreting tumor, salt-wasting renal disease, Cushing syndrome
• Patients with recent exogenous steroid administration or previous diuretics therapy