Dexmedetomidine is a selective alpha-2 adrenergic agonist that can be considered as an adjuvant to propofol or inhalational anesthetics. Dexmedetomidine mediate its cardiovascular effect through activation of receptors in central and peripheral nervous system. The classic cardiovascular response of dexmedetomidine is the biphasic with initial short-term increase in blood pressure followed by long-lasting decrease in BP and HR. There were several reports about these hemodynamic changes of dexmedetomidine, but not the evaluation of direct effects on cardiac function. The purpose of this study is to evaluate the effects of dexmedetomidine as an anesthetic adjuvant on cardiac function by using the transesophageal echocardiography.

Inclusion Criteria:

1. Above 20 years of age.
2. American Society of Anesthesiologists (ASA) Physical Status I, II, III.
3. general anesthesia

Exclusion Criteria:

1. severe functional liver or kidney disease
2. diagnosed HF ( NYHA class >3)
3. arrhythmia or received treatment with antiarrythmic drug .
4. severe bradycardia (HR < 45 bpm) and AV block
5. pathologic esophageal lesion (esophageal stricture or varix )
6. pregnancy