Trendelenburg (Head-Down tilt) and head rotation: Ultrasonographic effects on the internal jugular vein for catheterization safety.

Most guidelines fail to specify patient positioning during central venous catheterization. The objective was to determine the effects of head-down tilt (Trendelenburg position) and head rotation on the internal jugular vein (IJV). A prospective, observational, longitudinal, and descriptive study using healthy adult volunteers, of both sexes, was performed.