[Ultrasound-guided interscalene block: Influence of anatomic variations in clinical practice].

OBJECTIVES: This study aimed to evaluate visibility of interscalenic brachial plexus (IBP) variations with ultrasonography (US). Secondary end-point compared success rate of the interscalene block (IB) in shoulder surgery with or without the presence of variation.

STUDY DESIGN: Retrospective descriptive study, conducted in two University Departments of Anesthesiology.

PATIENTS AND METHODS: One hundred and forty-six (27 volunteers and 46 patients) high-resolution US of interscalene region were reviewed. Single shot IB in 46 patients were analyzed over the first 30 minutes comparing groups with variation or not.

RESULTS: Forty-nine percent (71/146) regions presented at least one visible variation by US. Thirty-three percent (48/146) showed an intramuscular passage of a root, 8% (12/146) showed a C5 root ahead of the anterior scalene muscle and 23% (33/146) an artery crossing the roots or trunks. Thirty-seven percent (54/146) presented an artery close to the plexus which could be close to the needle. In the forty-six IB performed, the presence of a variation did not show any difference in the sensitive and motor blocks at the 30th minute (p>0.05).

CONCLUSION: The high-resolution cervical US highlights the IBP variations. These variations appear not to have any relevant influence on the performance of the single shot IB.