Optimal Insertion Depth of Gastric Decompression Tube with a Thermistor for Patients Undergoing Laparoscopic Surgery in Trendelenburg Position

Abstract

Monitoring core temperature is crucial for maintaining normothermia during general anesthesia. Insertion of a gastric decompression tube (GDT) may be required during laparoscopic surgery. Recently, a newly designed GDT with a thermistor for monitoring esophageal temperature has been introduced. The purpose of the present study was to evaluate the optimal insertion depth of a GDT with a thermistor. Forty-eight patients undergoing elective laparoscopic surgery in the Trendelenburg position were included in the study. The GDT was inserted to a depth of nose–earlobe–xiphoid distance (NEX) + 12 cm and withdrawn sequentially, 2 cm at a time, at 5-min intervals. Temperatures of the GDT thermistor were compared with the core temperature of the tympanic membrane (TM) using Bland and Altman analysis. The correlation between optimal insertion depth of the GDT and anatomical distance (cricoid cartilage to the carina, CCD; carina to the left hemidiaphragm, CLHD) was evaluated, and a mathematical model to predict the optimal insertion depth of the GDT with a thermistor was calculated. Temperatures of TM and GDT thermistor at NEX + 4 cm showed good agreement and strong correlation, but better agreement and stronger correlation were seen at the actual location with the most minor temperature differences. The optimal insertion depth of the GDT was estimated as −15.524 + 0.414 × CCD − 0.145 × CLHD and showed a strong correlation with the actual GDT insertion depth (correlation coefficient 0.797, adjusted R2 = 0.636). The mathematical formula using CCD and CLHD would be helpful in determining the optimal insertion depth of a GDT with a thermistor.

Appropriate depth for the esophageal stethoscope placement for temperature monitoring - a pilot study

“…The sample size was predetermined based on the results of the previous study [1,8]. We assumed the correlation coefficient of determination as 0.64 for the pilot study [9], and the sample size was calculated as 13 with a=0.05 and b=0.20.…”

“…The difference between the esophageal temperature and the core body temperatures of TM was used to evaluate the accuracy of the esophageal temperature according to the IDE. The mean difference in temperatures between -0.5 o C and 0.5 o C, which equals ± 1.96 standard deviations (SD) of the Bland-Altman limits of agreement, was assumed as the clinically acceptable accuracy [1,8]. Bland-Altman analysis was performed to evaluate the difference between the esophageal temperatures and core body temperatures obtained from TM, and the location with the best Bland-Altman limits of agreement was set for the appropriate IDE.…”