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Axillary Temperature, as Recorded by the iThermonitor WT701, Well Represents Core Temperature in Adults Having Noncardiac Surgery

Pei, Lijian, MD*,†; Huang, Yuguang, MD*,†; Mao, Guangmei, PhD, MPH‡,§; Sessler, Daniel, I., MD§

doi: 10.1213/ANE.0000000000002706
Technology, Computing, and Simulation: Original Clinical Research Report

BACKGROUND: Core temperature can be accurately measured from the esophagus or nasopharynx during general anesthesia, but neither site is suitable for neuraxial anesthesia. We therefore determined the precision and accuracy of a novel wireless axillary thermometer, the iThermonitor, to determine its suitability for use during neuraxial anesthesia and in other patients who are not intubated.

METHODS: We enrolled 80 adults having upper abdominal surgery with endotracheal intubation. Intraoperative core temperature was measured in distal esophagus and was estimated at the axilla with a wireless iThermonitor WT701 (Raiing Medical, Boston MA) at 5-minute intervals. Pairs of axillary and reference distal esophageal temperatures were compared and summarized using linear regression and repeated-measured Bland–Altman methods. We a priori determined that the iThermonitor would have clinically acceptable accuracy if most estimates were within ±0.5°C of the esophageal reference, and suitable precision if the limits of agreement were within ±0.5°C.

RESULTS: There were 3339 sets of paired temperatures. Axillary and esophageal temperatures were similar, with a mean difference (esophageal minus axillary) of only 0.14°C ± 0.26°C (standard deviation). The Bland–Altman 95% limits of agreement were reasonably narrow, with the estimated upper limit at 0.66°C and the lower limit at −0.38°C, thus ±0.52°C, indicating good agreement across the range of mean temperatures from 34.9°C to 38.1°C. The absolute difference was within 0.5°C in 91% of the measurements (95% confidence interval, 88%–93%).

CONCLUSIONS: Axillary temperature, as recorded by the iThermonitor WT701, well represents core temperature in adults having noncardiac surgery and thus appears suitable for clinical use.

From the *Department of Anesthesiology, Peking Union Medical College Hospital, Beijing, China

Outcomes Research Consortium, Cleveland, Ohio

Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio

§Department of Outcomes Research, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio.

Published ahead of print December 29, 2017.

Accepted for publication September 29, 2017.

Funding: This work was supported by the Raiing Medical, Boston, MA. None of the authors has a personal financial interest in this research. The sponsor was not involved in data analysis or interpretation.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Reprints will not be available from the authors.

Address correspondence to Yuguang Huang, MD, Department of Anesthesiology, Peking Union Medical College Hospital (PUMCH), 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China. Address e-mail to (

© 2018 International Anesthesia Research Society
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