Comparison of Dexmedetomidine and Remifentanil Infusion During CABG

• serum potassium concentration [ Time Frame: at 24 hour before anesthetic induction ] [ Designated as safety issue: Yes ]
  serum potassium concentration at the day before anesthetic induction
  
  
• serum potassium concentration [ Time Frame: 1 minutes before anesthetic induction ] [ Designated as safety issue: Yes ]
  1 minutes before anesthetic induction (etomidate injection)
  
  
• serum potassium concentration [ Time Frame: 20 minutes after start of anesthetic induction ] [ Designated as safety issue: Yes ]
  serum potassium concentration 20 minutes after start of anesthetic induction (at the end of anesthetic induction)
  
  
• serum potassium concentration [ Time Frame: 2 hour after the start of anesthetic induction ] [ Designated as safety issue: Yes ]
  serum potassium concentration at 2 hour after anesthetic induction (after mammary artery dissection and graft formation)
  
  
• serum potassium concentration [ Time Frame: 3 hour after start of anesthetic induction ] [ Designated as safety issue: Yes ]
  serum potassium concentration at 3 hour after end of anesthetic induction (after the anastomosis of coronary graft)
  
  

• arterial blood gas analysis results [ Time Frame: 24 hour, 1 min before anesthetic induction, 20 min, 2 and 3 hour after the start of anesthetic induction ] [ Designated as safety issue: Yes ]
  arterial blood gas analysis results
  
  
• incidence of hypokalemia [ Time Frame: 24 hour, 1 min before anesthetic induction, 20 min, 2 and 3 hour after the start of anesthetic induction ] [ Designated as safety issue: Yes ]
  incidence of hypokalemia (serum K < 3.5) incidence of hypokalemia (serum K < 4.5)
  
  
• hemodynamic parameters [ Time Frame: 24 hour, 1 min before anesthetic induction, 20 min, 2 and 3 hour after the start of anesthetic induction ] [ Designated as safety issue: Yes ]
  hemodynamic parameters (blood pressure, heart rate, central venous pressure, cardiac output, SvO2)
  
  
• inotropics, vasopressor requirement [ Time Frame: 24 hour, 1 min before anesthetic induction, 20 min, 2 and 3 hour after the start of anesthetic induction ] [ Designated as safety issue: No ]
  inotropics, vasopressor requirement
  
  
• Myocardial injury marker [ Time Frame: 2, 24, 48 hour after the end of surgery ] [ Designated as safety issue: No ]
  serum concentration of CK-MB, Troponin (i)as a marker for myocaridial injury
  
  
• Left ventricular function [ Time Frame: 72 hour before, during (immediate after grafting), 72 hour after surgery ] [ Designated as safety issue: No ]
  left ventricular function determined by Tei index, ejection fraction of preoperative, intraoperative, postoperative echocardiography
  
  

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.