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

Official title

A Prospective Observational Method-Comparison Study of the Agreement Among Nasopharyngeal Temperature Probe, TaiDoc TD-1261 Infrared Tympanic Thermometer, and 3M SpotOn™ Zero-Heat-Flux Skin Sensor for Intraoperative Core Temperature Monitoring in Adult Patients Undergoing Elective Surgery Under General Anesthesia

Overview

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.

Detailed description

Background: Inadvertent perioperative hypothermia (IPH), defined as a core body temperature \< 36.0°C, affects 20-90% of patients undergoing general anesthesia and is associated with coagulopathy, surgical site infection, morbid cardiac events, and prolonged drug metabolism. Accurate intraoperative temperature monitoring is mandated by professional society guidelines.

Study design: Prospective, single-center, triple-method observational agreement study at Srinagarind Hospital, Khon Kaen University, Thailand. All three thermometry modalities are applied simultaneously in each participant. No intervention is assigned; temperature monitoring is additional to standard perioperative care.

Methods: After induction of general anesthesia and tracheal intubation, the nasopharyngeal (NP) probe (reference standard), TaiDoc TD-1261 infrared tympanic thermometer (test method 1), and 3M SpotOn™ zero-heat-flux forehead sensor (test method 2) are placed. Simultaneous temperature readings are recorded at 15-minute intervals from 15 minutes after induction until surgery end. For the TD-1261, two consecutive readings are taken at each time point and averaged; pinna retraction and fresh disposable probe cover are used at every measurement. The SpotOn™ sensor requires a 10-minute equilibration period before the first recorded value.

Statistical analysis: Primary analysis uses repeated-measures Bland-Altman analysis (Myles \& Cui, 2007 framework) to estimate bias and limits of agreement (LoA) for each method pair against the NP probe. Pre-specified clinical acceptability criterion: LoA within ±0.5°C (Sessler, 2008). Variance of differences is decomposed into between-subject (σ²\_B) and within-subject (σ²\_W) components. Secondary analyses: proportional bias assessment, sensitivity/specificity for hypothermia detection (NP \< 36.0°C), intraclass correlation coefficient (ICC, two-way mixed-effects model), and multivariable linear mixed-effects regression for clinical covariates. Sample size: 92 patients (Lu et al., 2016 method; 80% power; α = 0.05; SD of differences = 0.30°C for NP vs. TM; LoA acceptability threshold ±0.50°C; 15% dropout allowance).

This study provides the first institution-specific, population-specific evidence on temperature monitoring agreement in Thai surgical patients and constitutes the first published intraoperative validation of the TaiDoc TD-1261 infrared tympanic thermometer.

Primary outcome measures

• Limits of Agreement Between Each Test Method and the Nasopharyngeal Probe [Time frame: From 15 minutes after anesthesia induction until end of surgery; measurements recorded at 15-minute intervals (estimated total observation window: 60-195 minutes per participant)]

Secondary outcome measures (7)

• Systematic Bias (Mean Difference) of Each Test Method vs. NP Probe [Time frame: From 15 minutes after anesthesia induction until surgery end (15-minute intervals)]
• Proportional Bias Assessment [Time frame: From 15 minutes after anesthesia induction until surgery end]
• Sensitivity and Specificity for Hypothermia Detection [Time frame: From 15 minutes after anesthesia induction until surgery end]
• Intraclass Correlation Coefficient [Time frame: From 15 minutes after anesthesia induction until surgery end]
• Percentage of Paired Measurements Within ±0.5°C [Time frame: From 15 minutes after anesthesia induction until surgery end]
• Clinical Covariate Association With Method Difference [Time frame: Baseline characteristics collected before surgery; temperature data from 15 minutes post-induction until surgery end]
• Incidence of Device-Related Adverse Events [Time frame: From device placement until surgery end]

Eligibility criteria

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.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Observational model

Cohort

Study locations

Thailand · 1 center

• Faculty of Medicine, Khon Kaen University — Khon Kaen

Publications

• Wang J, Liang H, Tian C, Rong G, Shao X, Ran C. Agreement of zero-heat-flux thermometry compared with infrared tympanic temperature monitoring in adults undergoing major surgery. Eur J Med Res. 2025 Jan 30;30(1):60. doi: 10.1186/s40001-025-02317-9. PMID 39885585
• Iden T, Horn EP, Bein B, Bohm R, Beese J, Hocker J. Intraoperative temperature monitoring with zero heat flux technology (3M SpotOn sensor) in comparison with sublingual and nasopharyngeal temperature: An observational study. Eur J Anaesthesiol. 2015 Jun;32(6):387-91. doi: 10.1097/EJA.0000000000000232. PMID 25693138
• Wan L, Shen PY, Zhang SX, Wang LZ. Agreement of infrared ear temperature with nasopharyngeal temperature and diagnostic performance on hypothermia in general anesthetized patients. J Chin Med Assoc. 2022 Nov 1;85(11):1093-1097. doi: 10.1097/JCMA.0000000000000770. Epub 2022 Jul 6. PMID 35797551
• Lu MJ, Zhong WH, Liu YX, Miao HZ, Li YC, Ji MH. Sample Size for Assessing Agreement between Two Methods of Measurement by Bland-Altman Method. Int J Biostat. 2016 Nov 1;12(2):/j/ijb.2016.12.issue-2/ijb-2015-0039/ijb-2015-0039.xml. doi: 10.1515/ijb-2015-0039. PMID 27838682
• Cork RC, Vaughan RW, Humphrey LS. Precision and accuracy of intraoperative temperature monitoring. Anesth Analg. 1983 Feb;62(2):211-4. PMID 6829923
• Torossian A. Thermal management during anaesthesia and thermoregulation standards for the prevention of inadvertent perioperative hypothermia. Best Pract Res Clin Anaesthesiol. 2008 Dec;22(4):659-68. doi: 10.1016/j.bpa.2008.07.006. PMID 19137809
• Matsukawa T, Sessler DI, Sessler AM, Schroeder M, Ozaki M, Kurz A, Cheng C. Heat flow and distribution during induction of general anesthesia. Anesthesiology. 1995 Mar;82(3):662-73. doi: 10.1097/00000542-199503000-00008. PMID 7879935
• Sessler DI. Temperature monitoring and perioperative thermoregulation. Anesthesiology. 2008 Aug;109(2):318-38. doi: 10.1097/ALN.0b013e31817f6d76. PMID 18648241

Identifiers

NCT: NCT07749209 · HE691250

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗