Neuroimaging Study of Dexmedetomidine-Induced Analgesia

Inclusion Criteria: * Between the ages of 18 to 45 * Normal body weight and habitus, BMI ≤ 30 * Non-smoker * American Society of Anesthesiologists (ASA) physical status classification P1 * Active health insurance coverage * Fully vaccinated against COVID-19 Exclusion Criteria: * Cardiovascular: myocardial infarction, coronary artery disease, peripheral vascular disease, arrhythmia, congestive heart failure, valvular disease, hypertension * Respiratory: bronchitis, chronic obstructive pulmonary disease, smoking, shortness of breath * Hepatic: hepatitis, jaundice, ascites * Neurologic: seizure, stroke, positive neurologic findings on neurologic examination, multiple sclerosis, Meniere's disease, Parkinson's disease, neuropathy, peripheral stenosis * Gastrointestinal: esophageal reflux, hiatal hernia, ulcer * Endocrine: diabetes, thyroid disease * Renal: acute or chronic severe renal insufficiency * Hematologic: blood dyscrasias, anemia, coagulopathies, on anticoagulant therapy * Musculoskeletal: prior surgery or trauma to head neck or face, arthritis, personal or family history of malignant hyperthermia * Psychiatric: history or treatment for an active psychiatric problem, depression * Reproductive: pregnancy, breast-feeding * Medications: regular use of prescription and non-prescription medications expected to affect CNS function, St. John's Wort * Allergies: dexmedetomidine, ondansetron, glycopyrrolate, phenylephrine * Dermatologic: ulcerative skin conditions or other dermatologic conditions which could interfere with blood pressure cuff placement. * MRI reasons for exclusion: History of head trauma, surgical aneurysm clips, cardiac pacemaker, prosthetic heart valve, neurostimulator, implanted pumps, cochlear implants, metal rods, plates, or screws, intrauterine device, hearing aid, dentures, metal injury to eyes, metallic tattoos anywhere on the body or near the eye.