Effects Of Head Rotation On The Anatomic Relationship Of The Internal Jugular Vein And The Common Carotid Artery–an Ultrasonographic Study

Background and objective: The overlap between internal jugular vein(IJV) and common carotid artery(CAA) has been thought to be a risk of carotid artery injury when practicing internal jugular vein catheterization. Amounts of researches using ultrasound find that the anatomic relationship of IJV and CAA could be affected by head rotation. Scans have been performed from different angles lateral to the neck, but misleadingly depict the relationship of the IJV to the CCA. In this study, we observe the relationship of IJV and CAA by scanning strictly from the anterior to posterior using ultrasound at different head rotation.Methods: This study is a repeated measure design and a total of 131 patients were enrolled. By using ultrasonic scanning, the anatomic features of IJV and CAA both at thyroid cartilage level(prominentia laryngea level) and at the apex of the angle formed by the division of the sternocleidomastoid muscle(triangle level) with 0°, 15°, 30° and 45° right rotation were observed. Based on the ultrasound images, the cross sectional area(S) together with the width(W) of IJV and CAA, the safe puncture range, the overlapping ratio, the angle between the horizontal axis and the line from the midpoint of RIJV to that of CAA(α angle), as well as the distance including the skin to the midpoint of RIJV were measured. In addition, we analyzed the population whose W overlapping ratio was greater than 10% or 20%, and we considered the overlapping ratio larger than 20% as positive case. Furthermore, we divided the relationships between the IJV and CAA to anterior-lateral, lateral, posterior-lateral and extremely-posterior-lateral position according to α angle. We conducted counting statistics in these four regions with different rotations.Results: 1. No gender differences were found with regard to the cross section area and width of CAA at different rotations. Both cross section area and width of RIJVincreased compared to 0°, while there were no significant differences among 15° to 45°. 2. At both levels, the safe puncture range of RIJV increased parallelly with head rotation within 0° to 30°, and there was no statistical difference between 30° and 45°. 3. At prominentia laryngea level, the overlapping degree decreased as head rotation increased from 0° to 30°, and no statistical difference was found between 30° and 45°. There were no significant differences among different rotations at triangle level. 4. At both prominentia laryngea and triangle levels, RIJV located mainly at lateral and posterior-lateral positions. Besides, α angle extended along with gradually increasing RIJV shifted to lateral position while head rotation changing from 0° to 45°. 5. The distance including the skin to the midpoint of RIJV decreased as head rotation increasing. 6. CAA at triangle level was smaller than that at prominentia laryngea level, while RIJV was thicker and the safe puncture area was larger. In addition, the overlapping degree was less and the ratio of lateral position was higher than prominentia laryngea level at the same head rotation.Conclusion: The puncture conditions for RIJV catheterization were more optimal at 30° to 45° of head rotation. RIJV located mainly at lateral and posterior-lateral positions at different rotations and RIJV gradually shifted to lateral position while head rotation increasing. It would be much better to select triangle level for central venous catheterization than prominentia laryngea level.