Sympathetic activity could be increased during robot-assisted laparoscopic radical prostatectomy, which is performed in a steep trendelenburg position under CO2 pneumoperitoneum.

Stimulation of the sympathetic nervous system prolongs the QT interval and can increases the susceptibility to life threatening cardiac arrhythmias.

Dexmedetomidine has sympatholytic effects and potential antiarrhythmic properties. Perioperative administration of dexmedetomidine is a potential preventive and treatment strategy for tachyarrhythmia. Thus the investigators decided to evaluate the effect of dexmedetomidine on heart-rate corrected QT interval during robot-assisted laparoscopic radical prostatectomy. Furthermore, the investigators evaluated the Tp-e, Tp-e/QT ratio and Tp-e/QTc ratio as well.

Inclusion Criteria:

1. ASA class I-II
2. Otaining written informed consent from the patients who were undergoing robot- assisted laparoscopic radical prostatectomy

Exclusion Criteria:

1. Emergency operation
2. Cardiac disease (unstable angina, congestive heart failure, valvular heart disease)
3. Ventricular conduction abnormality
4. Prior pacemaker insertion
5. Abnormal electrolyte values
6. Patients who take antiarrythmic agent
7. Hepatic or renal failure
8. Drug hyperactivity
9. Neurological or psychiatric illnesses