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

Background: 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.

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

Methods: 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.

Results: 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.

Conclusion: 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.