Effect of head rotation on vascular anatomy of the neck: an ultrasound study.

Carotid artery injury is a serious complication of landmark-guided internal jugular catheterization. Studies have determined that the internal jugular vein (IJV) frequently overlaps the carotid artery (CA), which has been postulated to increase the rate of arterial injury. The purpose of this study was to define the anatomic relationship of the IJV and CA by describing CA overlap by the more superficial IJV. We also seek to determine the effect of head rotation on the amount of overlap, which may have implications for IJV catheter placement. We prospectively studied the vascular anatomy of the neck in 156 Emergency Department patients. The primary intervention was head rotation to the left, as if the patient was positioned for right IJV catheterization. The patient's head was positioned at 0, 45 and 90 degrees of rotation. Ultrasound images were obtained in a transverse orientation. The percentage overlap of the CA by the IJV was measured. We also measured the distance between the jugular vein and the carotid artery. In neutral position, there was a mean overlap of 29% at the apex of the sternocleidomastoid. As the head was turned, the percent overlap increased. At 90 degrees, there was a mean overlap of 72%. Differences were determined to be significant by analysis of variance (ANOVA) with a p < 0.001. Furthermore, we found a distance of 10 mm between IJV and CA when the head is in neutral position. As the head was turned, the jugular-carotid distance decreased to 1 mm in the far lateral head position. These differences were also found to be significant by ANOVA with a p < 0.001. We concluded that the IJV overlaps the CA in the neutral position to a significant degree. This overlap increases until the head is fully turned, where most of the CA is overlapped by the IJV. This may help explain the mechanism of CA puncture. We propose two modifications to standard IJV line technique: minimize the patients' head rotation; and use ultrasound guidance for IJV catheterization.