Assessment of sonographic skills of novices for identification of anatomical structures in ultrasound guided axillary brachial plexus block

The axillary approach of brachial plexus block (AxBPB) is preferred for its relative safety and ease to perform and commonly performed for providing anesthesia and analgesia involving upper limb procedures below elbow like distal forearm, wrist and hand surgeries. Ultrasound guidance has helped not only in minimizing complications like inadvertent vascular puncture and neural injury, but also in improving block success and reduction in dose of local anesthetic requirement because of real-time visualization and drug deposition close to nerves. The information on the ability of novices to quickly and accurately identify the essential structures one needs to know while performing an AxBPB is scarce. This will provide insight into the aspects of education and training needed to impart the requisite knowledge for novices and aid in structured competency-based training before they perform ultrasound guided axillary block. This study aims to assess the accuracy and time taken for sonoanatomy identification of essential anatomical structures in the axillary brachial plexus block by novices.

Informed consent will be obtained from the 22 first- and second-year postgraduate students assessed to be eligible based on their ultrasound experience of performing less than five nerve blocks. The recruited resident doctors will be given training including structured e-learning tutorials, didactic lectures on ultrasound machine and physics, anatomy, ergonomics, scanning technique and sonoanatomy of axillary brachial plexus block, and hands-on volunteer scanning, by the investigator experienced with the technique. The students will then move on to scan the patients coming for elective surgeries before the start of their respective surgeries. Adult patients between the ages of 18-60 years coming for elective surgery will be recruited after obtaining written, informed consent. Obese individuals (BMI ≥ 30kg/m2) with any anatomical or pathological abnormality in the axillary area will be excluded. Performing the axillary block is not a part of this study. Participants other than the one performing the scan will not observe the procedure or be present in the scanning room. The side of the subject to be scanned will be randomised using a block randomisation table. The scanning will be performed using a same machine with a high-frequency (6-13MHz) linear transducer (Sonosite Edge II, Bothell, USA). Before the trainees perform the scan, the blinded investigator will scan to identify the structures and its relation, to rule out any anatomical variation. The resident doctors will be briefed about the structures to be identified with respect to axillary brachial plexus block, including median nerve, ulnar nerve, radial nerve and musculocutaneous nerve, axillary artery, axillary vein and conjoint tendon of lattisimus dorsi and teres major. Once they identify the structures, they will be asked to freeze the image and point the structure and label them before saving the image. They can unfreeze and proceed to identify other structures and continue to label them in a similar manner until all seven structures are identified and marked. They can identify and label multiple structures at a time too. Also, the time taken to identify will be noted in seconds, from the start of scanning to the time when the image was frozen to label a particular structure. The participants will not be corrected or provided feedback during or after performing the scan. The data will be collected by an anesthesiologist who is not a part of the data analysis. The images will be saved and reviewed later as correct or incorrect identification by the principal investigator experienced in ultrasound guided regional anesthesia, blinded to the person performing the scan. Failure to mark any structure will be interpreted as incorrect identification.