The Effects of Ketamine and Methadone on Postoperative Pain for Laminectomy

Inclusion Criteria:

• 18 - 80 years old of either gender, scheduled for elective lumbar laminectomy

Exclusion Criteria:

* American Society of Anesthesiologists (ASA) IV and above
* Intolerance, allergy, or contraindication to use of any medications used in this study
* Significant coronary artery disease (abnormal stress test, myocardial infarction

  * within the last 3 months)
* Increased intraocular pressure (e.g., untreated glaucoma)
* Uncontrolled hypertension (BP \> 140/90)
* Sleep apnea and currently on continuous positive airway pressure (CPAP)
* Increased intracranial pressure or clinical signs thereof
* History of intracranial surgery, stroke, or brain aneurysm
* Cardiac arrhythmias particularly prolonged QT syndrome
* Drugs known to cause prolonged qT: class (IA) antiarrhythmics (quinidine, procainamide, disopyramide), class III antiarrhythmics (sotalol, dofetilide, ibutilide, amiodarone), haloperidol, thioridazine, arsenic trioxide, HIV protease inhibitors, tricyclic antidepressants
* Individuals with significant psychological disorders including: schizophrenia, mania, bipolar disorder or psychosis
* Pregnant or lactating women
* Emergent laminectomy
* Those already receiving ketamine or methadone prior to surgery
* Morbid obesity (BMI \> 40 kg/m2) AND/OR weight \> 150 kg
* Chronic renal failure ( creatinine \> 2.0 mg/dL)
* Liver failure e.g., active cirrhosis
* Alcohol or substance abuse within in the past 3 months
* Uncorrected hypokalemia, hypomagnesemia, hypocalcemia (can be due to diuretics, mineralocorticoid use, laxatives)
* Chronic obstructive pulmonary disease (COPD)/Hypercarbia
* Restrictive lung disease (pulmonary fibrosis, myasthenia gravis)
* Congestive heart failure
* Thyroid disease
* Organ transplant patients
* Drugs/substances known to inhibit methadone metabolism: macrolide antibiotics e.g., erythromycin, cimetidine, astemizole, voriconazole, grapefruit juice