Managing acute-on-chronic pain in opioid-tolerant individuals is complex and challenging; exploring new analgesia regimens for this population is essential. Ketamine is an N-methyl D-aspartate antagonist that blocks transmission of painful stimuli and could be a useful medication for this patient population. A new low-dose ketamine protocol as an adjunct to conventional pain therapy was implemented in a major urban Level 1 trauma center in Canada. A retrospective before-and-after chart review was conducted to explore the research question, “What is the effect of low-dose ketamine continuous intravenous infusions on pain of highly opioid-tolerant adults following spinal surgery?”.