The purpose of this study is to evaluate the effect of dexmedetomidine on hemodynamic responses during laryngoscopy and double lumen endotracheal intubation and assess the adverse effect related to complications of dexmedetomidine.

The cardiovascular responses to laryngoscopy and tracheal intubation are mediated by both sympathetic and parasympathetic nervous system. The hemodynamic responses resulting from sympathetic nervous system stimulation are tachycardia, cardiac arrhythmias, hypertension, increased intraocular pressure, increased intracranial pressure, bronchospasm and myocardial ischemia. Tachycardia is one of the major predictor of intraoperative myocardial ischemia and causes an imbalance of myocardial oxygen supply and demand. Although hemodynamic responses to laryngoscopy and intubation is transient, these effect may be harmful to patients suffering from myocardial and cerebrovascular diseases. The placement of double lumen endotracheal tube may produce similar or greater pressor response than endotracheal tube because of larger sizes and greater carinal stimulation.

Inclusion Criteria:

• ASA Physical Status I-III
• Undergoing Elective Thoracotomy or Thoracoscopy
• Required Left Sided-double Lumen Endotracheal Intubation

Exclusion Criteria:

• Patients with bradycardia (heart rate < 50 beat per minute) or heart block
• Suspected of Difficult Intubation
• Patients Who Are at Risk for Rapid Change of Hemodynamics
• Allergic to Dexmedetomidine
• Hepatic or Renal Impairment (Preoperative Serum Creatinine > 1.5 mg/dl)
• Pregnancy