PURPOSE: The primary aim of this project was to decrease the incidence of postoperative delirium after spine surgery. DESIGN: A prospective preimplementation and postimplementation design was used. METHODS: A reduced dose ketamine protocol was implemented for adult patients undergoing elective spinal fusion surgery. Thirty patients were assessed at five time points for the presence of postoperative delirium in the postanesthesia care unit (PACU) using the 3-Minute Diagnostic Interview for Confusion Assessment Method Defined Delirium tool and opioid requirements were compared. FINDINGS: A statistical difference was noted between two groups in the incidence of delirium at three of five time points: on arrival to the PACU, and at 60 and 90 minutes after arrival to the PACU. CONCLUSIONS: This pilot study establishes groundwork for further studies to investigate if the ketamine dose can decrease the incidence of postoperative delirium in the initial 90 minutes after surgery without decreasing its analgesic effect.