Risk factors for hypothermia in patients undergoing general anesthesia in the postanesthesia care unit

Objective: To investigate the incidence of hypothermia and its risk factors in patients after general anesthesia in the post anesthesia recovery unit (PACU). Methods: A total of 10 341 patients after general anesthesia in the PACU of Peking University People's Hospital from January to December 2019 were retrospectively reviewed. According to whether hypothermia occurred in the PACU, the patients were divided into hypothermia group and non-hypothermia group. After propensity score matching based on age and gender, 336 cases in hypothermia group and 336 cases in non-hypothermia group were finally included. The clinical characteristics of the two groups were compared, and the potential risk factors of hypothermia in the PACU were analyzed by multivariate logistic regression model. Results: The incidence of hypothermia in PACU was 3.3% (339/10 341). The age of hypothermia group was (54.1±17.1) years, with 156 males and 180 females; the age of non-hypothermia group was (53.1±16.0) years, with 156 males and 180 females. There was no statistically significant difference in age, gender, American Society of Anesthesiologists (ASA) classification and operation type between the two groups (all P>0.05). Compared with the non-hypothermia group, the body mass index (BMI) [(22.8±3.5) kg/m2 vs (24.7±4.2) kg/m2] and baseline body temperature [(36.3±0.5)℃ vs (36.5±0.5)℃] were lower, and anesthesia time [(4.4±1.6) h vs (3.2±1.5) h] and operation time [(3.1±1.4) h vs (2.1±1.3) h] were longer in hypothermia group. The amount of intraoperative bleeding, blood transfusion and intravenous fluid was larger in hypothermia group (all P<0.001). Multivariate logistic regression analysis showed that larger amount of blood loss (L) (OR=5.361, 95%CI: 2.863-10.037, P<0.001), prone position operation (OR=3.653, 95%CI: 2.104-6.342, P<0.001), longer anesthesia time (h) (OR=1.421, 95%CI: 1.227-1.646, P<0.001), and general anesthesia combined with regional nerve block (OR=1.708, 95%CI: 1.026-2.843, P=0.039) were independent risk factors of hypothermia in the PACU, and higher BMI (OR=0.849, 95%CI: 0.801-0.900, P<0.001) was an independent protective factor. Conclusions: The incidence of hypothermia in patients after general anesthesia in the PACU remains relatively high. Therefore, more attention should be paid to identify high-risk patients, and active preventive measures should be taken for the risk factors of hypothermia.