The aim of this clinical investigation is to prove that the thermal suit with forced-air warming is more effective to prevent inadvertent intraoperative hypothermia than conventional warming methods. The study group will have the thermal suit from arriving to the hospital until to the ward after surgery. In the operating theatre forced-air warming device will be connected to the trouser legs of the thermal suit and the device will be turned on during surgery. The control group will have normal hospital clothes. Intraoperative warming will be managed with the warming mattress and a forced-air warming blanket. The primary endpoint is core temperature after arriving to the post-anaesthesia care unit.

Inclusion Criteria:

• primary breast cancer surgery
• unilateral resection or mastectomy with or without axillar lymphadenectomy
• body mass index 25-40

Exclusion Criteria:

• ASA > III
• decreased mental status
• inadequate Finnish language skills
• other than general anaesthesia