Inclusion criteria | |
Age 18 to 55 years inclusive | |
Scheduled for general anesthesia where 50% nitrous oxide in oxygen would be used | |
Endotracheal intubation or laryngeal mask airway insertion would be used | |
Afebrile (preoperative oral or temporal scan temperature between 36.2 and 37.4 °C inclusive) | |
Positioned supine or lithotomy | |
Forced air warming would be used | |
Expected duration of anesthetic to be at least 60 min | |
Exclusion criteria | |
Emergency surgery or any other aspiration risk | |
Age < 18 years or > 55 years | |
Pregnant | |
Incarceration | |
Febrile illness | |
Anticipated difficult airway | |
Contraindication to nitrous oxide use | |
Contraindication to nasal instrumentation | |
Nasal surgery | |
Current or recent epistaxis | |
Requirement for foreign language interpreter | |
Allergy to propofol | |
Malignant hyperthermia risk | |
Inability to oxygenate on less than 50% oxygen | |
Cardiac surgery | |
Neuro-surgery | |
Receiving vasoactive infusions | |
Significant valvular heart disease | |
Unstable cardiac disease | |
Requiring prone or lateral positioning | |
Inability to provide informed consent | |
Inability to use forced air warming | |
Untreated hypo- or hyper-thyroidism | |
ASA class 4, 5 or 6a | |
Anticipated inability to tolerate any of the 4 different anesthetic induction options in this study |