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

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.

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

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.

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).

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.