Study Objective: To compare the cross-sectional area (in cm²) of the left internal jugular vein (LIJV) and right internal jugular vein (RIJV) in anesthetized children, and measure the response to the Trendelenburg tilt position (TBRG) and a positive inspiratory pressure hold.

Design: Prospective, nonrandomized study.

Setting: University medical center.

Patients: 45 ASA physical status I and II children, ages 6 months to 8 years, undergoing general anesthesia and mechanical ventilation.

Interventions: The cross-sectional area of both internal jugular veins was measured with a 5-MHz, two-dimensional surface transducer, at the level of the cricoid cartilage. Three measurements were obtained: 1) with the patient supine, 2) during a 10-second breath-hold with a positive inspiratory pressure (PIP) of 20 cm H₂O, and 3) with the patient at 20 degrees TBRG. Data were analyzed with two-way analysis of variance (ANOVA) and Student-Newman-Keuls test, with a p < 0.05 considered significant.

Measurements and Main Results: In supine patients, the cross-sectional area of the RIJV was larger than the LIJV in 31 patients (69%), and equal or smaller in 14 patients (31%) (0.80 ± 0.38 vs. 0.59 ± 0.22; p = 0.002). A PIP hold, but not TBRG, significantly dilated the RIJV (0.8 ± 0.38 at baseline vs. 0.93 ± 0.42 with TBRG; p = not significant vs. 1.1 ± 0.46 with PIP; p < 0.05), whereas neither maneuver was effective with the LIJV.

Conclusions: The cross-sectional area of the RIJV is often greater than the LIJV; the TBRG was not effective to increase the cross-sectional area of the internal jugular veins, and only a PIP hold increased significantly the cross-sectional area of the RIJV. In this study, the LIJV appeared of smaller size and less compliant compared with the RIJV.