Background: Perioperative hypothermia is common in patients undergoing general anaesthesia and is associated with important adverse events. The 'gold standard' for monitoring body core temperature - the pulmonary artery catheter - is invasive and unsuitable for most patients. For routine clinical practice, other sites and methods of temperature monitoring are commonly used.
Objective: The aim of this study was to evaluate a new temperature sensor (3M SpotOn) using the 'zero heat flux' method attached to the forehead, and compare it to sublingual and nasopharyngeal sensors in terms of correlation, accuracy and precision.
Design: An observational study.
Setting: University Medical Center Schleswig Holstein, Campus Kiel, Germany from October 2013 to January 2014.
Patients: One hundred and twenty patients scheduled for elective gynaecological or trauma surgery undergoing general anaesthesia were enrolled into this study. Data of 83 patients were finally analysed. Patients with unexpected blood loss, haemodynamic instability determined by the need for continuous norepinephrine infusion and/or need for postoperative ventilation were excluded from this study.
Intervention: Temperature monitoring was established after induction of anaesthesia with sublingual and nasopharyngeal probes, and the SpotOn sensor.
Main outcome measures: Body temperature was measured 15, 45 and 75 min after induction of anaesthesia from sublingual and nasopharyngeal probes and the 3M SpotOn sensor at precisely the same moment.
Results: Analysis of 83 data sets revealed that 3M SpotOn temperatures were almost identical with nasopharyngeal temperatures (mean difference 0.07 °C; P = 0.1424) and slightly lower than sublingual temperatures by 0.35 °C (P < 0.0001). Coefficients of determination (r) for both methods were between 0.87 (SpotOn vs. nasopharyngeal measurement) and 0.77 (SpotOn vs. sublingual measurement). Bland-Altman analysis revealed a bias (SD) between 0.07 °C (0.21) (SpotOn vs. nasopharyngeal) and -0.35 °C (0.29) (SpotOn vs. sublingual measurement).
Conclusion: With respect to correlation, accuracy and precision, the 3M SpotOn sensor provides a good measurement of body temperature in comparison to the nasopharyngeal probe and an acceptable measurement in comparison with sublingual thermometry. It is adequate for clinical use.
Trial registration: Clinicaltrials.gov identifier: NCT02031159.