Accuracy of Non-invasive Temperature Measurement in Deep Hypothermia; a Prospective Cohort Study

The study is a prospective cohort study on patients undergoing elective thoracic surgery in deep hypothermia. The goal is to assess the accuracy of non-invasive temperature devices compared to a gold standard representing core temperature.

At the study hospital, Oslo University Hospital Rikshospitalet, patients undergoing thoracic surgery will already have several routes of temperature monitoring as part of standard procedure. Before cardiopulmonary bypass bladder temperature is normally used as a reference for core temperature. After cardiopulmonary bypass is established, temperature is monitored directly in the circulating blood, hence reflecting core temperature.

For measuring the epitympanic temperature we will use the Metraux Epitympanic Thermometer (Walpoth, Galdikas et al. 1994), a nasopharyngeal temperature probe (Mon-a-Therm, General Purpose Temperature Probe 12Fr/Ch, Covidien) and a new transcutaneous device (SpotOn 3M). The temperature will be measured in degrees Celsius. The first reading will be noted just after induction of anaesthesia and compared to the bladder temperature. After cardiopulmonary bypass (CPB) is established and therapeutic hypothermia is induced, the values for both non-invasive and blood temperature will be recorded every minute. After reaching the target temperature according to the blood temperature, we will continue recording the non-invasive temperature until relative similarity is established. The process will be repeated during re-warming.