No effect of Valsalva maneuver or Trendelenburg angle on axillary vein size

A new technique for establishing ultrasound-guided central access involves the use of the axillary vein, the distal projection of the subclavian vein, via the lateral chest.

To examine the effects of Valsalva maneuver and Trendelenburg positioning on axillary vein cross-sectional area (CSA).

Using a group-sequential design, we enrolled stable emergency patients and measured their axillary veins sonographically. Patients were measured while supine, then after a Valsalva maneuver, and then at 5°, 10°, 15°, and 17° of Trendelenburg positioning, pausing 2 min after each change. We asked patients to score their discomfort from 0 to 10 in each position.

We enrolled 30 adult patients with a median age of 39 years (range, 20-66 years). Treating physicians considered 11 of these patients to have hypovolemia. The Valsalva maneuver decreased CSA (Mean difference = -0.03 cm(2)), (95% confidence interval [CI] -0.10-0.04). Trendelenburg positioning did not statistically increase CSA. The 5° position caused the largest increase, that is, 0.04 cm(2) (95% CI -0.04-0.12) in the entire group and 0.1 cm(2) (95% CI -0.07-0.28) in the hypovolemic subgroup. At greater degrees of Trendelenburg positioning, patients reported higher discomfort scores or simply dropped out.

The Valsalva maneuver and Trendelenburg angles above 10° do not increase axillary vein area but do increase patient discomfort. Our data suggest optimal positioning in the supine resting position or at a 5° Trendelenburg position.