In a study of anaesthetised infants and children, the right internal jugular vein as assessed by ultrasonography was measured with the head in the neutral position, and then at 40 degrees and 80 degrees of rotation to the contralateral side. The 40 degree position resulted in an increase in IJV diameter but with less overlap with the carotid artery than the 80 degree position. The authors conclude that rotating the head 40 degrees to the left results in the best balance of increased IJV diameter versus overlap with the carotid.
Effects of head rotation on the right internal jugular vein in infants and young children
Anaesthesia Volume 65, Issue 3, Pages 272-276