Hypothermia occurs frequently during general anesthesia. This study is to evaluate the efficacy of 10 minutes of prewarming and warmed fluid during urologic surgery.

During general anesthesia, vasodilation distributes body heat and leads to hypothermia. Especially during urologic operation (transurethral resection of bladder and prostate), bladder irrigation worsens hypothermia. Hence, various methods are used to maintain core temperature during operation.

Previous studies have demonstrated that prewarming of the patient is effective in maintaining core temperature perioperatively. However, more than 50% of patients who have applied prewarming for more than 30 minutes preoperatively are reported to fall in hypothermia. Hence, developing simple and effective method to prevent hypothermia is expected.

Hence, the investigators planned to examine the effect of active warming (10 minutes of prewarming preoperatively and prewarmed intravenous fluid intraoperatively) on hypothermia in patients undergoing urologic operation under general anesthesia.

Inclusion Criteria:

• patients undergoing urologic surgery(transurethral resection of bladder, prostate)

Exclusion Criteria:

• moderate to severe cardiopulmonary, renal impairment
• thyroid disease
• any infection sign
• abnormal temperature prior to induction of general anesthesia (<36'C or >37.5'C)
• refusal to participate in the study
• unable to understand the study