prospective randomized double-blind controlled study

Total of 69 ASA (American Society of Anesthesiologist) physical status class I or II patients will be enrolled.

Randomly assigned to three group according to the depth of guide-wire prior to tissue dilation during central catheterization via right internal jugular vein. (Group 1: 15 cm / Group 2: 17.5 cm / Group 3: 20 cm)

Central catheterization will be performed by anesthesiologists who be blinded to this study protocol.

An investigator will monitor and record whether any arrhythmia will occur.

The incidence of occurrence of arrhythmia will be compared between three groups.

Inclusion Criteria:

• patients receiving general anesthesia requiring central venous catheterization via right internal jugular vein.
• ASA (American Society of Anesthesiologist) physical status class I or II

Exclusion Criteria:

• at the pre-anesthetic evaluation, history of any arrhythmia
• when monitoring before the induction of anesthesia in the operating room, newly arrhythmia is observed.
• abnormal electrolyte at the pre-anesthetic evaluation
• too difficult to access right internal jugular vein for central catheterization (too short neck, infection at the site of right internal jugular vein, ventriculoperitoneal shunt or chemo-port existence at the site of right internal jugular vein. too close site to operating field)