Dynamic variation of the axillary veins due to intrathoracic pressure changes: A prospective sonographic study

The ultrasound-guided axillary vein is becoming a compulsory alternative vessel for central venous catheterization and the anatomical position offers several potential advantages over blind, subclavian vein techniques.

To determine the degree of dynamic variation of the axillary vein size measured by ultrasound prior to the induction of general anesthesia and after starting controlled mechanical ventilation.

Prospective, observational study.

One hundred ten patients undergoing elective surgery were enrolled and classified according to sex, age, and body mass index. Two-dimensional cross-sectional vein diameter, area, and mean flow velocity were performed using ultrasound on both the left and right axillary veins of each subject before and after induction of anesthesia.

There was statistically significant evidence showing that the axillary vein area increases when patients are mechanically ventilated. When considering venous flow velocity as a primary outcome, velocity decreased after patients moved from spontaneous to mechanical ventilation (coefficient = -0.267), but this relationship failed to achieve statistical significance (t = -1.355, p = 0.179).

Anatomical variations in depth and diameter as well as the collapsibility due to intrathoracic pressures changes represent common challenges that face clinicians during central venous catheterization of the axillary vein. A noteworthy increase in vessel size as patients transition from spontaneous to mechanical ventilation may theoretically improve first-pass cannulation success with practitioners skilled in both ultrasound and procedure. As a result, placing a centrally inserted central catheter after the induction of anesthesia may be beneficial.