A prospective observational study testing liquid crystal phase change type thermometer placed on skin against oesophageal/pharyngeal placed thermometers in participants undergoing general anesthesia

Abstract

Background: Patient outcomes are influenced by intraoperative temperature management. Oesophageal/pharyngeal temperature monitoring is the standard of care at our institute but is not well tolerated in awake patients. Many non-invasive temperature monitors have been studied. Only the TraxIt® Wearable Children's Underarm Thermometer which contains liquid crystals that undergo phase changes according to temperature is available at our institution. We tested these non-invasive monitors against our standard of care which is the oesophageal/pharyngeal temperature monitor. Methods: We conducted a prospective observational study of 100 patients receiving general anaesthesia for elective surgery. Patients were eligible for inclusion if they were ≥ 18 years old, were planned to have a general anaesthetic > 60 min during which no body cavity (chest or abdomen) would be opened. Patient temperature was measured with an oesophageal/pharyngeal thermistor probe and skin surface temperature monitors placed over the forehead, in the axilla, over the sternum, and behind the ear (over major vessels to the brain). Temperatures were recorded and then analysed using Altman-Bland plots. Pre-determined clinically relevant limits of agreement were set at-/+ 0.5 °C. Results: From the 100 patients we collected 500 data points for each monitor with an average monitoring time of 102 min (30-300 min) across a range of surgical procedures. None of the skin surface temperature monitors achieved the pre-determined limits of agreement and results were impacted by the use of a forced air warmer. Conclusion: The TraxIt® Wearable Children's Underarm Thermometers are not suitable for temperature monitoring during general anaesthesia.