The Effects of Heated Humidified Gases on Body Temperature and Shivering in Patients under General Anesthesia

Purpose: This study was performed to determine the effects of heated humidified anesthetic gases, via a heated and humidified circuit (HHC), on body temperature and shivering. Methods: A quasi-experimental design with pretest and posttest measures was used. Data was collected from 71 patients who underwent musculoskeletal surgery for clavicle or upper arm fractures under general anesthesia from June 4 to September 31, 2009. The experimental group consisted of 34 patients who received heated and humidified gas through a HHC, which was set at 40 ̊C, and continued to be warm during the period from the endotracheal tube intubation to extubation. The control group was made up of 37 patients who were provided with gas through a standard breathing circuit system with no added heat and humidity. The collected data was analyzed by chi-square test and t-test. Results: The esophageal temperature was significantly higher in the experimental group at 20, 30 and 40 minutes after intubation compared with those of the control group. However, there were no differences in the tympanic membrane temperature and in the level of shivering between the two groups. Conclusion: The finding partially supports evidence for applying HHC in patients undergoing surgery under general anesthesia to prevent hypothermia. However, further studies are required to measure the effects of HHC on body temperature and shivering over time considering different results among researches.