Interscalene block using ultrasound guidance: impact of experience on resident performance.

Background: We evaluated the weekly progress of anesthesiology residents performing an interscalene block with ultrasound guidance (UG) for block success rates and for the specific time intervals: (i) time to image the brachial plexus and (ii) time from insertion of the block needle until motor stimulation occurred. Our primary objective was to characterize the influence of experience over the course of the regional anesthesia rotation on the performance of a UG interscalene block by anesthesiology residents.
Methods: Residents conducted an interscalene block with UG under the supervision of attending anesthesiologists experienced in this technique. Block efficacy, time intervals required to perform the block, and acute complications were recorded. We compared success rates over the course of the rotation, and analyzed process time data with respect to trainee level of experience, week of the trainee rotation, and patient body habitus.
Results: Twenty-one trainees conducted 222 blocks over a consecutive 7-month period. Block success rate was 97.3%, and did not change significantly over the course of the 4-week rotation. Total block time and imaging time significantly decreased over the 4-week rotation, while the needle insertion-to-stimulation time did not change. Slower imaging time was predicted by obesity.
Conclusion: The success rates for a UG interscalene block provided by supervised residents were initially high, and remained so throughout the 4-week rotation. Trainees required less time to image the nerves and to perform the block over the course of the rotation.