The optimal degree of neck rotation during internal jugular vein (IJV) cannulation remains undetermined because previous studies suggested using sonography, but without puncturing the vein. We assessed whether a neutral position (NP) of the head (0 degrees) during ultrasound-guided cannulation of the IJV was safer than rotating the neck to 45 degrees head turned. The effect of these 2 positions during ultrasound-guided cannulation on major complications was the primary outcome