Udompornmongkol, V. “The effect of intravenous dexmedetomidine to intrathecal bupivacaine on spinal block duration in orthopedic surgery: a double blind controlled study”. Thai Journal of Anesthesiology, vol. 43, no. 4, Jan. 2018, pp. 316-27, https://he02.tci-thaijo.org/index.php/anesthai/article/view/110602.