Ultrasound evaluation of the anatomical characteristics of the internal jugular vein and carotid artery--facilitation of internal jugular vein cannulation.

BACKGROUND AND PURPOSE Literature review revealed major variations in the anatomic characteristics of the right internal jugular vein (IJV) and carotid artery (CA) by the use of the ultrasound machine. The purpose of this study is to examine the anatomical characteristics of the right IJV and CA and to evaluate the IJV cannulation outcomes by the standard ultrasound guided vs. ultrasound localized technique as suggested by Lin and colleagues. Additionally, the study assessed the impact of changing the ultrasound transducer direction on the location of right IJV relative to the CA METHODS: Patients (n = 100) were randomly assigned to either and ultrasound-guided or ultrasound-localized technique for IJV cannulation. The 'Site Rite' II ultrasound transducer was directed perpendicular to the floor at the apex of the clavicle-sternocleidomastoid triangle at the level of the cricoid cartilage with the head turned to contralateral side of cannulation and table tilted to 30 degrees in Trendelenburg position. Cannulation outcomes, including successful cannulation, access time, success time, and difficult cases were evaluated. Aborted difficult cases included prolonged procedural time exceeding four minutes and carotid puncture, and these were examined by technique, IJV size and its location relative to CA. The location of the IJV relative to CA was evaluated firstly with the ultrasound transducer directed perpendicular to the floor and secondly with the transducer directed perpendicular to the skin (Fig 1). RESULTS With the ultrasound transducer directed perpendicular to the floor, the depth of the IJV from the skin (15 mm) was comparable to its diameter (14.1 mm), while the CA A-P diameter was around half that of the IJV (7.4 mm) (Table 2). Also, the majority of patients showed lateral (51%) and posterolateral (14%) positions of the IJV relative to the CA. Directing the transducer perpendicular to the skin resulted in more anterolateral positions (77%) with 6% total overlap. Cannulation of the IJV was successful in 94% in both randomization groups, with 91.5% of the patients achieving first pass cannulation in the ultrasound-guided group and 87.2% in the ultrasound-localized (Table 3). Access time (6.9 +/- 13 sec and 5.9 +/- 14.6 sec) and success time (13.5 +/- 14.2 sec and 13.2 +/- 15.0 sec) were comparable for both groups. Reasons for aborted difficult cannulation included prolonged procedural time in 2% and carotid puncture in 4%, in both techniques. Compared to the successful cases, difficult cases were characterized by a significantly greater degree of anterolateral (exceeding 15 degrees) location ofthe IJV relative to the CA(p-value = 0.046) and a significantly smaller IJV size (mean 10.3 mm vs. 14.3 mm, p-value = 0.035) (Table 4). However, in multivariate analysis controlling for the technique utilized, only the relation between the size of IJV and the occurrence of difficult cases remained significant. With each 1 mm decrease in IJV size, there was a 37% significant increase in the risk of difficult cases. CONCLUSIONS Findings of the study show that both ultrasound guided and ultrasound localized techniques yield similar cannulation outcomes. Additional to the anteraloteral position of the IJV relative to the CA, a small IJV size constitutes a powerful predictor for the incidence of prolonged procedure time and carotid puncture for IJV canulation. Finally, the transducer direction has a significant impact on the assessment of the location of the IJV relative to the CA.