Agreement of infrared ear temperature with nasopharyngeal temperature and diagnostic performance on hypothermia in general anesthetized patients.

Background: Infrared ear thermometry is widely used in clinical practice due to its noninvasive, convenient, and quick sampling. However, its accuracy and feasibility in anesthetized patients have not yet been established.

Methods: We conducted this cross-sectional study to evaluate the agreement between infrared ear temperature and nasopharyngeal temperature in general anesthetized patients and its performance in intraoperative hypothermia, defined as nasopharyngeal temperature <36°C. Adult female patients who underwent gynecological surgery under general anesthesia were enrolled in this study. Infrared ear temperature by Braun ThermoScan PRO 4000 (Braun GmbH, Kronberg, Germany) and nasopharyngeal temperature were measured simultaneously before, during, and after surgery. The agreement between the two temperatures was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. The diagnostic performance of the infrared ear thermometer for hypothermia was evaluated using receiver operating characteristic (ROC) curve analysis.

Results: Fifty-six patients with 168 pairs of simultaneous infrared ear and nasopharyngeal temperatures were included in this analysis. The mean infrared ear temperature was consistently higher than the nasopharyngeal temperature throughout surgery, but the differences were small (0.22, 0.13, and 0.06°C before, during, and after surgery, respectively). The ICC between the two temperatures before, during, and after surgery was 0.70, 0.75, and 0.80, respectively, and 93.5% of the differences fell within the 95% limits of agreement of ±0.5°C. An infrared ear thermometer had high diagnostic accuracy for hypothermia, with an area under the ROC curve of 0.95 (95% confidence interval [CI], 0.92-0.98). The cutoff of infrared ear temperature for hypothermia was 36.2°C with a sensitivity of 0.89 (95% CI, 0.71-0.98) and a specificity of 0.87 (95% CI, 0.81-0.92).

Conclusion: The infrared ear temperature is in good agreement with the nasopharyngeal temperature in general anesthetized patients without hyperthermia and has high performance for detecting hypothermia. An infrared ear thermometer can be a diagnostic tool for intraoperative hypothermia.