To test the hypothesis that approaching the internal jugular vein with the needle bevel down would produce less injury to the vessel wall compared to the bevel up approach during central venous catheterization.

Inclusion Criteria:

• patients undergoing surgery that requires the placement of a central venous catheter at the internal jugular vein

Exclusion Criteria:

• anatomical anomaly in the neck region
• recent history of central venous catheterization