The effect of metrics-based feedback on acquisition of sonographic skills relevant to performance of ultrasound-guided axillary brachial plexus block.

The objective of this study was to examine the effect of metrics-based vs. non-metrics-based feedback on novices learning predefined competencies for acquisition and interpretation of sonographic images relevant to performance of ultrasound-guided axillary brachial plexus block. Twelve anaesthetic trainees were randomly assigned to either metrics-based-feedback or non-metrics-based feedback groups. After a common learning phase, all participants attempted to perform a predefined task that involved scanning the left axilla of a single volunteer. Following completion of the task, all participants in each group received feedback from a different expert in regional blocks (consultant anaesthetist) and were allowed to practise the predefined task for up to 1 h. Those in the metrics-based feedback group received feedback based on previously validated metrics, and they practised each metric item until it was performed satisfactorily, as assessed by the supervising consultant. Subsequently, each participant attempted to perform ultrasonography of the left axilla on the same volunteer. Two trained consultant anaesthetists independently scored the video recording pre- and post-feedback scans using the validated metrics list. Both groups showed improvement from pre-feedback to post-feedback scores. Compared with participants in the non-metrics-based feedback group, those in the metrics-based feedback group completed more steps: median (IQR [range]) 18.8 (1.5 [17-20]) vs. 14.3 (4.5 [11-18.5]), p = 0.009, and made fewer errors 0.5 (1 [0-1.5]) vs. 1.5 (2 [1-6]), p = 0.041 postfeedback. In this study, novices' sonographic skills showed greater improvement when feedback was combined with validated metrics.

Construct validity of a novel assessment tool for ultrasound-guided axillary brachial plexus block.

The purpose of this study was to examine the construct validity and reliability of a novel metrics-based assessment tool, previously developed for ultrasound-guided axillary brachial plexus block. Five expert and eight novice anaesthetists performed a total of 18 ultrasound-guided axillary brachial plexus blocks on the same number of patients. A trained investigator video-taped procedures according to a pre-defined protocol. Two trained consultant anaesthetists independently scored the videos using the assessment tool. Compared with novices, experts completed more steps (mean 41.0 vs. 33.1, p = 0.001), had fewer procedural errors (2.8 vs. 7.9, p < 0.0001), had fewer critical errors (0.8 vs. 1.3, p = 0.030), and fewer total errors (3.5 vs. 9.1, p < 0.0001). The mean inter-rater reliability for scoring of experts' performance was 0.91, for novices' performance was 0.84, and for all performance combined (n = 18) was 0.88. This assessment tool is valid, and discriminates reliably between expert and novice performance for placement of ultrasound-guided axillary brachial plexus blocks.

Nerve localization techniques for peripheral nerve block and possible future directions.

BACKGROUND: Ultrasound guidance is now a standard nerve localization technique for peripheral nerve block (PNB). Ultrasonography allows simultaneous visualization of the target nerve, needle, local anesthetic injectate, and surrounding anatomical structures. Accurate deposition of local anesthetic next to the nerve is essential to the success of the nerve block procedure. Due to limitations in the visibility of both needle tip and nerve surface, the precise relationship between needle tip and target nerve is unknown at the moment of injection. Importantly, nerve injury may result both from an inappropriately placed needle tip and inappropriately placed local anesthetic. The relationship between the block needle tip and target nerve is of paramount importance to the safe conduct of peripheral nerve block. METHODS: This review summarizes the evolution of nerve localization in regional anesthesia, characterizes a problem faced by clinicians in performing ultrasound-guided nerve block, and explores the potential technological solutions to this problem. RESULTS: To date, technology newly applied to PNB includes real-time 3D imaging, multi-planar magnetic needle guidance, and in-line injection pressure monitoring. This review postulates that optical reflectance spectroscopy and bioimpedance may allow for accurate identification of the relationship between needle tip and target nerve, currently a high priority deficit in PNB techniques. CONCLUSIONS: Until it is known how best to define the relationship between needle and nerve at the moment of injection, some common sense principles are suggested.