In the modified Seldinger's maneuver, after guide-wire insertion into the right internal jugular vein, "we will measure the distance between the skin puncture site and the outside of anterior wall of the jugular vein. Next, we will insert the dilator on the guidewire by the measured length."

In the modified Seldinger's maneuver, after guide-wire insertion into the right internal jugular vein, "we will insert the dilator on the guidewire as commonly used method of the practitioners."

For soft tissue dilation just after guidewire insertion in central venous catheterization through the right internal jugular vein, investigators will measure the distance between the skin puncture site and outside of anterior wall of the vein with real-time ultrasonography in the measured depth group. Next, practitioner will insert the dilator by the measured length and continue to insert the central venous catheter. For the conventional group as a control group, practitioner will perform the central venous catheterization with a manner used routinely by the practitioner.

hematoma from the vascular wall puncture by the dilator

distance between skin puncture site and the outside of the anterior wall of the internal jugular vein which will be measured by real-time ultrasonography