Ultrasonographic assessment of internal jugular vein diameter and its relationship with the carotid artery at the apex, middle, and base of the triangle formed by two heads of sternocleidomastoid muscle: A pilot study in healthy volunteers

BACKGROUND: Anteroposterior (AP) diameter of internal jugular vein (IJV) and its relative position with carotid artery (CA) varies in the triangle formed by two heads of sternocleidomastoid muscle, which is the site of insertion of needle for IJV cannulation. This study assessed the maximum AP diameter of the IJV in supine and Trendelenburg positions and during Valsalva maneuver (supine position) at the apex, middle, and base of the triangle and to study the relationship of the IJV with the CA. MATERIALS AND METHODS: Twenty-five healthy volunteers were included and ultrasonography of IJV was performed in supine and Trendelenburg positions and during Valsalva maneuver (supine position) at the apex, middle, and base of the triangle bilaterally. The AP diameter of IJV was measured. The relative anatomical position of IJV was assessed as anterior (A), anterolateral (AL), or lateral (L) to CA in neutral head position and 30°, 45°, and 90° head rotation to the contralateral side in supine position. RESULTS: The difference in right IJV diameter was significant (P = 0.001) between supine vs. Trendelenburg position at the base of the triangle. Within one position there was significant difference between apex and base of the triangle. The left IJV diameter was significantly different between supine vs. Trendelenburg position at the apex (P = 0.004), middle (P = 0.003), and base of the triangle (P-value = 0.001). There was significant difference between supine vs. Valsalva maneuver at the middle (P = 0.011) and base (P = 0.014) of the triangle. The right IJV was more L or AL to the CA in apex with head in neutral or 30° rotation. The left IJV was more L or AL to the CA in middle with head in neutral position. CONCLUSION: Trendelenburg and Valsalva increase diameter of IJV on both right and left side. Diameter of IJV is greater at the base of the triangle. IJV is lateral or anterolateral when the head is either neutral or turned 30° to the contralateral side.