Effect of Buprenorphine on Characteristics of Ultrasound-Guided Supraclavicular Brachial Plexus Block With Levobupivacaine and Bupivacaine-A Prospective Double-Blind Randomized Controlled Trial - Pushpavathi Ture; Ashwini H R; Jyothi B; Ajay Ture; Likhith L M; Kalaivani S (Indian Journal of Health Sciences and Biomedical Research KLEU, 2026)