A Comparison of Intra-op Ketamine vs Placebo in Patients Having Spinal Fusion
Condition: Postoperative Pain
MeSH terms: Pain, Postoperative
Intervention: Ketamine; Placebo
Intervention description: Infusion at a rate of 10 mcg/kg/min; Placebo IV
Intervention MeSH terms: Ketamine
Phase: Phase 4
Study type: Interventional
Primary purpose: Other
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Enrollment: 46.0
Sex: All
Minimum age: 18 Years
Healthy volunteers: No
Keywords: Anesthesia Recovery Period; Spinal Fusion

Summary:

      Postoperative pain is severe after major spine surgery. Opioids such as morphine and
      hydromorphone are routinely used for postoperative pain control. These drugs have significant
      side effects, most importantly respiratory depression, nausea, constipation and tolerance.
      Moreover, many spine surgery patients have used opioid pain medication for back pain long
      term, leading to pre-surgical opioid tolerance and increased postoperative pain. This has led
      to a search for adjuvant medications to reduce the use of opioids and reduce opioid mediated
      side effects and tolerance.

      Ketamine is an intravenous anesthetic with analgesic properties in subanesthetic doses.
      Ketamine is a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors. NMDA
      receptors are involved in central pain sensitization via wind-up phenomenon and altered pain
      memory, a process which can be blocked by ketamine. NMDA receptor antagonists may prevent the
      development of tolerance to opioids and hyperalgesia. Ketamine has been safely used to
      decrease pain in numerous studies. Ketamine can also act as an antidepressant with hours of
      administration.

      Ketamine has rapid brain uptake and subsequent re-distribution with a distribution half-life
      of 10-15 minutes and an elimination half-life of 2 hours. Ketamine does not cause respiratory
      depression.
    

Eligibility criteria:

        Inclusion Criteria:

          1. Adult (>/=18)

          2. male or female

          3. Undergoing surgery for multilevel (>2 level) spinal fusion from a posterior approach.

          4. General anesthesia

          5. English speakers such that they can complete the pain score and satisfaction
             questionnaires whose scores are a critical outcome variable.

          6. If female, subject is non-lactating and is either: a. Post-menopausal or post
             hysterectomy; b. Of childbearing potential but is not pregnant at time of baseline as
             determined by pre-surgical pregnancy testing.

          7. Subject is American Society of Anesthesiologists (ASA) physical status 1, 2, or 3.

        Exclusion Criteria:

          1. Cognitively impaired (by history)

          2. Subject with a history of psychosis

          3. Subject known to have significant hepatic disease

          4. Subject for whom opioids or ketamine are contraindicated

          5. Patients with narrow angle glaucoma

          6. Increased intracranial or intraocular pressure

          7. If female, is either pregnant or lactating.