Chest. 2013 Feb 7. doi: 10.1378/chest.11-2462. [Epub ahead of print] PMID: 23392444

BACKGROUND: The Trendelenburg position is used to distend the central veins, improving both success and safety of vascular cannulation. The purpose of this study was to measure the cross-sectional area (CSA) of the internal jugular vein (IJV) in three different positions using surface ultrasound.

METHODS: Fifty one subjects were enrolled. A Sonosite Titan 180 or M-Turbo portable ultrasound machine with a 10.5 mHz broadband linear surface probe was used. We measured the CSA of the IJV (at end-expiration at the level of the cricoid cartilage) in three positions: 15 degrees reverse Trendelenburg, supine, and 15 degrees Trendelenburg.

RESULTS: The mean CSA at 15 degrees reverse Trendelenburg was 0.83 cm2 (Std Dev 0.86), in the supine position it was 1.25 cm2 (Std Dev 0.98) and at minus 15 degrees Trendelenburg it was 1.47 cm2 (Std Dev 1.03). Moving from reverse Trendelenburg to supine, CSA increased 50 percent. In contrast, lowering the head to a Trendelenburg position increased mean CSA only 17 percent. Surprisingly, Trendelenburg positioning reduced CSA in 9 of 51 subjects.

CONCLUSIONS: Trendelenburg positioning augments CSA only modestly, on average, compared with the supine position, and in some patients reduces the CSA. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT01099254.

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