Dexmedetomidine Versus Ketamine Combined With Fentanyl for Sedation-Analgesia in Colonoscopy Procedures: A Randomized Prospective Study - Pourfakhr, Pejman; Nouri, Khaton; Shariefnia, Hamid Reza; Moharari, Reza Shariat; Khajavi, Mohammad Reza (Acta Medica Iranica, 2019)