A Study of Heat Loss in Patients Undergoing General Anesthesia Warmed with a Heated Mattress with Esophageal Temperature Monitoring Compared to Facial Infrared Thermography

摘要

Patients under general anesthesia are at risk from lowering of body temperature. In major surgery procedures temperature should be monitored. An infrared camera can be an alternative method for monitoring temperature during general anesthesia. This study was designed to investigate if central temperature can be monitored in noninvasive way during general anesthesia using an infrared camera, in order to study the efficiency of heated surgical mattresses. 52 Patients over 50 years old, under 30 BMI, elected for procedures of over 2 hours were included. The patients were randomized in to two groups, (n = 23) without additional warming during general anesthesia, and those (n = 29) heated with a warm mattress set to a temperature of 39 degrees C. The groups did not statistically differ in demographic data or the onset temperature. Esophageal central temperature for both groups showed a similar trend in patient heat loss up to 1 hour 30 minutes after intubation, respectively from 36.49 +/- 0.46 degrees C to 35.79 +/- 0.64 degrees C in the unheated group and from 36.45 +/- 0.47 degrees C to 35.95 +/- 0.58 degrees C in the heated group. Patients from both groups continued cooling, but patients from the "warmed" group cooled slower than the controls. There was no statistical difference between groups at 1 hour 45 minutes (p = 0.19). Infrared data from the inner canthi showed similar temperature fall from 35.78 +/- 0.86 degrees C to 35.18 +/- 0.85 degrees C at 1 hour 30 minutes in the control group and 35.53 +/- 0.93 degrees C to 35.26 +/- 0.74 degrees C in the "warmed" group. A significant correlation was found between esophageal temperatures measures with infrared inner canthi of the eyes. (p < 0.001). This proves the possibility of monitoring temperature with infrared technology and also confirms the validity of infrared measurement at the inner canthi of the eyes to represent internal body temperature.