In order to further obtain information on the current status of temperature monitoring and perioperative warming practice in most parts of the country, to project incidence rate of perioperative hypothermia in most parts of the country, explore the relationship between perioperative hypothermia and postoperative clinical outcome, and to provide evidence for the improvement of perioperative body temperature management guidelines in accordance with characteristics of the current Turkish healthcare status, investigators will conduct surveys in department of anesthesiology over certain regions of Turkey to carry out a large scale prospective study. In the study, investigators will search the incidence rate of perioperative hypothermia in the surveyed areas, explore the causes of hypothermia, base on which it is expected to enable to project perioperative hypothermia incidence rate, to verify the effectiveness of perioperative hypothermia risk assessment questionnaire for patients under general anesthesia, and to provide guidance and evidence for the clinical practice of perioperative warming care.