Background: Prewarming with a forced-air warmer device at least 30 minutes before entering the operating room (OR) helps to prevent inadvertent perioperative hypothermia (IPH), although doing so on a regular schedule may be difficult. Prewarming for a short time may reduce IPH and is more practical.

Objective: To investigate the incidence of hypothermia in non-anesthetized volunteers who used a forced-air warmer device for 10 minutes before entering the OR.

Materials and Methods: The present study was a prospective, randomized-controlled trial that included 32 non-anesthetized volunteers. Sixteen volunteers were randomly assigned to receive prewarming using a forced-air warmer set at 38℃ for 10 minutes as the PW group and 16 other volunteers did not receive prewarming as the NW group, before entering a 20℃ OR for an hour. The primary outcome was the incidence of hypothermia in the OR. The secondary outcomes were a change in body temperature in the OR, thermal comfort, the requirement for an additional forced-air warmer device, and complications such as skin rash and burn.

Results: The incidence of hypothermia in the OR was 25% in the PW group and 18.75% in the NW group, with no statistically significant differences (p>0.999). There were no significant differences in body temperature between groups. In the waiting room, about 50% of the PW group and none of the NW group reported feeling hot discomfort (p=0.002). However, there were no significant differences in thermal comfort when entering the OR and PACU. No participant asked for an additional forced-air warmer device, and there were no observable device-related complications.

Conclusion: A short-term use of active prewarming cannot reduce the incidence of hypothermia in non-anesthetized volunteers.