1. Patient will be identified by surgeon and consented by member of the research team
2. Patient will be randomized to one of three groups on the day of surgery
3. Following securement of the endotracheal tube, the study medication will be administered over 10 minutes via an IV infusion pump.
4. The subject will receive ketamine, ketamine plus magnesium or a placebo.
5. Following surgery, the patient will be taken to the post anesthesia care unit (PACU) and set up with standard ASA monitoring as well as end-tidal CO2 via nasal cannula. A hydromorphone patient controlled analgesia (PCA) pump will be set-up by nursing and given to the patient. Standard dosing of 0.2 mg bolus, every 6 minutes with a maximum 2 mg will be the starting dose as is standard for these patients post-operatively.
6. Primary outcome will be the total amount of hydromorphone used in the first 24 hours post-operatively.
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