Ahmed, S., Hossain, M. M., & Khatun, U. S. (2014). Pre-emptive analgesia : effect of low dose Ketamine as pre-emptive analgesia in postoperative pain management after lower abdominal surgery. Journal of the Bangladesh Society of Anaesthesiologists, 17(1), 17–22. https://doi.org/10.3329/jbsa.v17i1.4046