Randomized, Double-blind, Placebo Controlled Study on the Effect of a Single Postoperative Administration of Low Dose Ketamine After Gastric Bypass and Gastrectomy Surgeries

This is a randomized, double-blind, placebo-controlled, two-arm parallel, single-center study. One hundred subjects (50 in each arm) will be enrolled. Subjects, between the ages 18 and 65, undergoing laparoscopic gastric bypass or sleeve gastrectomy will be recruited and consented during the preadmission visit prior to surgery. Eligible subjects will be randomized to one of the two treatment group in a 1:1 ratio to receive either IV ketamine (0.4mg/kg) or matching placebo. Both men and women will be recruited, and there is no limitation as to racial and ethnic origin. In the PACU, patients will receive either 0.4mg/kg IV ketamine or placebo. All patients will also receive standard post-anesthetic monitoring and care, as well as routine care after transfer out of the PACU. Patients are followed until the date of discharge, and endpoints (see below) are collected from patient reports as well as from medical charts. During their hospital stay (and once after their discharge from the hospital), patients will fill out five questionnaires which provide estimates of their postoperative pain control, mood and function, and quality of postsurgical recovery. An additional component of the study, which is entirely optional, is to obtain patient serum samples (about two teaspoons) in the operating room and 15 minutes and 4 hours after ketamine infusion. The investigators will use these samples to assess levels of IL-1, IL-6, TNF-α, and BDNF, which are markers for pain. In addition, with patient consent, the investigators will also store serum samples for future research use to measure other cytokines and neurotrophic factors and molecular markers associated with pain and depression.