Agreement Among Three Methods of Intraoperative Core Temperature Monitoring: Nasopharyngeal Probe, TaiDoc TD-1261 Infrared Tympanic Thermometer, and 3M SpotOn™ Skin Sensor

Keeping a patient's body temperature normal during surgery is an important part of safe anesthetic care. When the body temperature drops below 36°C (called inadvertent perioperative hypothermia), patients face higher risks of bleeding, wound infection, heart problems, and a slower recovery. To prevent these complications, anesthesiologists monitor core body temperature continuously during surgery. Three monitoring methods are commonly used in clinical practice: (1) a nasopharyngeal probe - a small soft sensor inserted through the nose and placed at the back of the throat, which provides continuous readings and is considered the gold standard; (2) an infrared tympanic thermometer (TaiDoc TD-1261) - a handheld device that measures ear temperature in about one second; and (3) the 3M SpotOn™ sensor - a non-invasive adhesive patch placed on the forehead that continuously estimates core temperature without requiring insertion into any body cavity. Although all three methods are used interchangeably at Srinagarind Hospital, no study has directly compared all three simultaneously in the same patient to determine how well they agree with each other. If significant differences exist between methods, a clinician who switches from one device to another may unknowingly under-detect or over-estimate hypothermia. This study will enroll 92 adult patients scheduled for elective surgery under general anesthesia at Srinagarind Hospital, Khon Kaen University. All three temperature sensors will be applied at the same time, and readings will be recorded simultaneously every 15 minutes throughout the operation. The main goal is to determine whether each device gives results close enough to the nasopharyngeal probe to be safely used as an alternative. The study is observational - no medications or procedures will be added to routine care.

Inclusion Criteria: * Age ≥ 18 years * We will include 3 independent groups of patients receiving general anesthesia with tracheal intubation: Group 1: Cardiac surgery Group 2: Thoracic surgery Group 3: General surgery, including neurosurgery * Expected surgical duration ≥ 60 minutes * ASA Physical Status Classification I- III * Able to provide written informed consent Exclusion Criteria: * Prior nasal surgery, nasal polyps, deviated nasal septum, or significant epistaxis history precluding safe nasopharyngeal probe insertion * Otitis media, tympanic membrane perforation, significant cerumen impaction, or external auditory canal deformity that would prevent reliable infrared tympanic temperature measurement * Facial or forehead skin lesions, burns, or known adhesive hypersensitivity at the planned 3M SpotOn™ application site, craniotomy, and head and neck surgery. * Baseline core temperature \< 35.0°C or \> 38.5°C at preoperative assessment * Planned use of neuraxial anesthesia as the primary or adjunct technique * Emergency procedures, pregnancy, or procedures involving deliberate hypothermia or cardiopulmonary bypass.