Thoracotomy for lung lesion does not affect the accuracy of esophageal temperature

There are several sites for measuring body temperature. Correct reading of core temperature is imperative for patients undergoing major operations under anesthesia. In certain situations, the sites of measurement may be close to the surgical area, and thus the measurement is easily prejudiced by the influence environment. We hypothesized that the body temperature, if monitored in the esophagus, would be lower than obtained from the tympanic membrane during thoracotomy for lung pathology under general anesthesia.

The study involved 32 patients, of American Society of Anesthesiologists (ASA) physical status I or II, who were to undergo elective thoracotomy for lung disorders. General anesthesia was induced with fentanyl, propofol, and rocuronium and maintained with sevoflurane in oxygen. The tympanic membrane probe was placed prior to when general anesthesia was administered, and the esophageal probe was inserted after administration of general anesthesia. Both the individualized temperatures were recorded at 5-minute intervals, and were compared at each change of surgical situation.

The tympanic membrane temperature was higher than esophageal temperature after initiation of one-lung ventilation (OLV) with statistical significance. The magnitude of decrease in temperature between two individualized temperatures, as compared from start of OLV, was greater in tympanic membrane temperature, especially at 30 minutes after OLV (p < 0.02, difference = -0.09 ± 0.22) and at the time point of the lowest temperature (p = 0.002, difference = -0.14 ± 0.24). There was no clinical difference of situation found (difference > 0.5°C) in the measuring sequences.

The accuracy of esophageal temperature seemed not to be affected during thoracotomy for lung lesion, in comparison with that of tympanic temperature. From clinical viewpoints, the monitoring of esophageal temperature could be more reliable in such surgical situation.