Prevalence and multivariable factors associated with inadvertent intraoperative hypothermia in video-assisted thoracoscopic surgery: a single-center retrospective study

BACKGROUND: Inadvertent intraoperative hypothermia increases the risk of adverse events, but its related risk factors have not been defined in video-assisted thoracoscopic surgery (VATS). This study aimed at analyzing the prevalence and factors related to inadvertent intraoperative hypothermia in adults undergoing elective VATS under general anesthesia. METHODS: This was a retrospective study using data from the Peking University People’s Hospital from January through December, 2018. Data were collected on age, sex, height, weight, American Society of Anesthesiologists physical status, the duration of preparation and surgery, timing of surgery, surgery types, anesthesia types, intraoperative core temperature and the length of stay (LOS) in the hospital from the electronic database in our center. Patients were covered with a cotton blanket preoperatively and the surgical draping during the operation. A circulation-water warming mattress set to 38 °C were placed under the body of the patients. Inadvertent intraoperative hypothermia was identified as a core temperature monitored in nasopharynx < 36 °C. Multivariate logistic regression analysis was used to identify independent risk factors of hypothermia. RESULTS: We found that 72.7% (95% CI 70.5 to 75.0%) of 1467 adult patients who underwent VATS suffered hypothermia during surgery. The factors associated with inadvertent intraoperative hypothermia included age (OR = 1.23, 95% CI 1.11 to 1.36, p < 0.001), BMI (OR = 1.83, 95% CI 1.43 to 2.35, p < 0.001), the duration of preparation (OR = 1.01, 95% CI 1.00 to 1.02, p = 0.014), the duration of surgery (OR = 2.10, 95% CI 1.63 to 2.70, p < 0.001), timing of surgery (OR = 1.64, 95% CI 1.28 to 2.12, p < 0.001), ambient temperature in the operating room (OR = 0.67, 95% CI 0.53 to 0.85, p = 0.001) and general anesthesia combined with paravertebral block after induction of anesthesia (OR = 2.30, 95% CI 1.31 to 4.03, p = 0.004). The average LOS in the hospital in the hypothermia group and the normothemic group was 9 days and 8 days, respectively (p < 0.001). CONCLUSIONS: We highlight the high prevalence of inadvertent intraoperative hypothermia during elective VATS and identify key risk factors including age, duration of surgery more than 2 h, surgery in the morning and general anesthesia combined with paravertebral block (PVB) after intubation. We also find that hypothermia did prolong the LOS in the hospital.