Effect of forced-air warming by an underbody blanket on end-of-surgery hypothermia: A propensity score-matched analysis of 5063 patients

Background: Underbody blankets have recently been launched and are used by anesthesiologists for surgical patients. However, the forced-air warming effect of underbody blankets is still controversial. The aim of this study was to determine the effect of forced-air warming by an underbody blanket on body temperature in anesthetized patients. Methods: We retrospectively analyzed 5063 surgical patients. We used propensity score matching to reduce the bias caused by a lack of randomization. After propensity score matching, the change in body temperature from before to after surgery was compared between patients who used underbody blankets (Under group) and those who used other types of warming blankets (Control group). The incidence of hypothermia (i.e., body temperature < 36.0 °C at the end of surgery) was compared between the two groups. A p value < 0.05 was considered to indicate statistical significance. Results: We obtained 489 propensity score-matched pairs of patients from the two groups, of whom 33 and 63 had hypothermia in the Under and Control groups, respectively (odds ratio: 0.49, 95% confidence interval: 0.31-0.76, p = 0.0013). Conclusions: The present study suggests that the underbody blanket may help reduce the incidence of intraoperative hypothermia and may be more efficient in warming anesthetized patients compared with other types of warming blankets. Trial registration: UMIN Clinical Trials Registry (Identifier: UMIN000022909; retrospectively registered on June 27, 2016).