Association Between Intraoperative Hypothermia and Preoperative Body Composition in Patients Undergoing General Anesthesia for Gastrointestinal Surgery.

Introduction General anesthesia induces a redistribution of deep body temperature drop, and a decrease in body temperature during surgery is associated with increased blood loss and transfusion requirements, increased incidence of wound infections, and prolonged hospital stays. Furthermore, low body mass index (BMI) is associated with a pronounced decrease in body temperature. However, subcutaneous fat mass, visceral fat mass, and skeletal muscle mass have not been precisely measured. More precise quantification of body composition can be achieved using computed tomography (CT) imaging, which allows the measurement of total fat, subcutaneous fat, visceral fat, and subcutaneous fat areas. Therefore, this study aimed to investigate whether differences in body composition obtained from CT images affect intraoperative temperature variations. Methods This was a single-center, retrospective observational study. The participants were Japanese patients who underwent elective gastrointestinal surgery under general anesthesia between April 1, 2021, and March 31, 2022. Hypothermia was defined as a core temperature of less than 36.0℃. Body temperature during surgery was measured by pharyngeal or bladder temperature, and patients who had a temperature of < 36.0℃ for at least one minute during anesthesia were classified into the hypothermia group, and all other patients were assigned to the control group. We investigated the relationship between fat mass, visceral fat mass, and skeletal muscle mass measured from preoperative CT images, along with preoperative blood sampling data and intraoperative body temperature. To standardize the estimated area, the index was calculated by dividing the heights of the two surpluses. The subcutaneous adipose tissue index (SATI) is the cross-sectional area of subcutaneous fat (cm2) divided by height2 (m2), and the visceral adipose tissue index (VATI) is the visceral adipose cross-sectional area (cm2) divided by height2 (m2). Statistical analysis was performed using the Mann-Whitney U test to compare the hypothermia and control groups. Logistic regression analysis was performed to identify the factors showing significant differences. Furthermore, receiver operating characteristic (ROC) analysis was performed, and the cutoff values were calculated. The significance level was set at p < 0.05. Results The analysis included 35 patients each in the hypothermia and control groups. SATI (cm²/ⅿ²) was significantly lower in the hypothermia group (median 27.91), compared to the control group (median 37.83) (p=0.033). VATI (cm²/ⅿ²) did not significantly differ between the hypothermia (median 32.62) and control groups (median 32.53) (p=0.828). Similarly, SMI (cm²/ⅿ²) exhibited no significant differences between the hypothermia (median 31.93) and control groups (median 34.65) (p=0.19). Univariate and multivariate logistic regression analyses were performed to identify the risk factors associated with the development of hypothermia. SATI was a significant factor in both univariate (OR: 5.45, 95%CI: 1.960-15.20, p=0.01) and multivariate analyses (OR: 5.520, 95%CI: 0.199-15.50, p> 0.001). Conclusions A decreased SATI was associated with intraoperative hypothermia in patients undergoing gastrointestinal surgery. Preoperative CT-based measurements of SATI may serve as a useful tool for predicting the risk of intraoperative hypothermia.