Special K infusion
This was a small but well done RCT of 48 patients presenting to the ED with painful conditions and pain score >5. Ketamine 0.3mg/kg was given either by IV push (5 minutes) or slow infusion (given over 15 minutes). Pain score was reduced the same in each group. The infusion group had marked reduction in feeling of unreality and was less sedated compared to the IV push group.

A prospective randomized, double-dummy trial comparing IV push low dose ketamine to short infusion of low dose ketamine for treatment of  pain in the ED.  Am J Emerg Med. 2017 Aug;35(8):1095-1100. doi: 10.1016/j.ajem.2017.03.004. Epub 2017 Mar 3.