Eligibility Criteria:
Inclusion Criteria:
* Between the ages of 18 to 45
* Normal body weight and habitus, BMI less than or equal to 30
* Non-smoker
* American Society of Anesthesiologists (ASA) physical status classification P1
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: labetalol, ondansetron, glycopyrrolate, ketamine, midazolam