Effect of shoulder positioning on ultrasonic visualisation of the subclavian vein in healthy adults: A prospective observational study

Introduction: Ultrasound guidance is commonly used during central venous cannulation. Subclavian vein is a commonly chosen site, but previous studies found varying results in the ideal positioning of the shoulder for subclavian vein cannulation. The objective of this study is to determine which shoulder position results in the greatest cross-sectional area of the right subclavian vein for cannulation. Methods: In this prospective observational study, ultrasound was performed on healthy adult volunteers to visualise the right subclavian vein in three different shoulder positions: neutral, abduction and retraction. A blinded independent investigator measured the cross-sectional areas by computer software using planimetry method. Statistical analysis was performed by one-way repeated measures analysis of variance. Results: Forty-four adults participated in the study. The mean cross-sectional area of the right subclavian vein in shoulder neutral, abduction and retraction positions were 1.05 ± 0.33 cm2, 1.01 ± 0.31 cm2 and 0.82 ± 0.28 cm2, respectively. When compared to shoulder retraction, the cross-sectional areas were significantly increased in shoulder neutral (P < 0.01) and abduction (P < 0.01) positions. There was no significant difference between shoulder neutral and abduction position (P = 0.71). Conclusion: Positioning the shoulder in neutral or abduction results in the greatest cross-sectional area of the right subclavian vein and may be more ideal for ultrasound guided cannulation.