Participants who are enrolled into the trial will undergo randomization into either the experimental or control arm by the IDS department at time of presentation to the hospital. The infusate will be prepared by the IDS department at a ketamine concentration of 500mg/250ml with all IV bags labeled "Investigational Ketamine / Placebo - PRO27024" prior to dispersal to the pre-operative nurse. All elective surgery patients will receive alvimopan beginning in the pre-operative area and administered by the RN at least 30 minutes prior to administration of narcotic medications. A total of 60 patients will be enrolled (see sample size calculation in c.2.3), 30 into each arm. All infusion rates will be calculated based on ideal body weight (IBW), unless actual body weight (ABW) is less than ideal. IBW is calculated for males as 50kg + 2.3*(number of inches over 5 feet) and for females as 45.5kg + 2.3*(number of inches over 5 feet). All investigational infusions will be started by the anesthesia resident or Certified Registered Nurse Anesthetists (CRNA) at the time of anesthesia induction. Patients will receive a bolus of the investigational solution at a calculated dose of 0.25 mg/kg over 5 minutes following anesthetic induction. A continuous infusion of the investigational solution will immediately follow at a rate of 2 mcg/kg/min. Timing of bolus administration along with time of initiation of continuous infusion will be documented with the continuous infusion to run for a duration of 48-hours.