The Lateral Decubitus Body Position Might Improve the Safety of Ultrasound-Guided Supraclavicular Brachial Plexus Nerve Block

BACKGROUND: To investigate whether body mass index (BMI) and changes in body positioning have any correlation with the distance from the pleura to the inferior trunk of the supraclavicular brachial plexus. PATIENTS AND METHODS: Twenty stroke patients with upper limb spasticity and complex regional pain syndrome were recruited for this study. Distance from the pleura to the inferior trunk was measured in the supine position, body turned sideways at 45 °, and in the lateral decubitus position. Correlations between BMI and measured distances in these body positions were evaluated. A linear musculoskeletal ultrasound transducer was used to conduct these distance measurements. RESULTS: The distance from the pleura to the inferior trunk in the supine position was calculated to have an average of 0.42 ± 0.06 cm (D1), 0.44 ±0.05 (D2) when lying sideways at 45 °, and 0.87 ± 0.08 cm (D3) in the lateral decubitus position. The Kruskal–Wallis test revealed significant differences when comparing D3 with D1, and D3 with D2 (p < 0.001). Positive correlations were observed between BMI and D1 (Spearman’s rho = 0.62, p = 0.004, two-tailed), and between BMI and D2 (Spearman’s rho = 0.61, p = 0.005, two-tailed). The strongest positive correlation was observed between BMI and D3 (Spearman’s rho = 0.78, p < 0.001, two-tailed). DISCUSSION: In the lateral decubitus body position, the distance from the pleura to the inferior trunk increased significantly by 2-fold and was positively correlated with BMI. The increased distance may improve the safety of the nerve block procedure. As a result, it is recommended that patients be placed in the lateral decubitus body position when performing ultrasound-guided supraclavicular brachial plexus nerve block of the inferior trunk.