This survey was anticipated to enroll 800 patients who underwent elective operations with general anaesthesia from 24 hospitals in Peking. After obtaining approval from the Ethical Committee related to research involving human subjects,the investigators will enroll the patients according to the inclusion and exclusion criterion. The tympanic temperature(measured by Braun PRO4000 Thermometer) will be monitored at the following time points respectively: arrived at waiting area, enter the OR room, 5 min before and after anesthesia induction, every 15 min during the operation, operation ended,arrived at PACU. Other information will also be collected, the investigators will record the type and dosage of anesthesia drug,duration of surgery and anesthesia, the patient warming method or if it is used.operation room temperature,the amount of the infusion of intravenous fluids and blood,etc. during the whole operation procedure. The other information will be followed up and recorded after the operation(within 30 days postoperation) which incudes ICU stays, hospital stays, incision infection, new cardiology events.etc.