Intraoperative active warming is usually performed by skin warming. There are several forced-air systems on the market; forced air warming is generally described as the most effective yet feasible method of patient warming. Augustine Biomedical (Eden Prairie, MN, USA) recently introduced a new patient warming system named "Hot Dog" with an active polymer warming upper-body blanket and a new under-body warming mattress. The polymer-heating devices consist of an electronic regulator and the polymer blankets, which are covered with a washable fabric. Conventional mains power the system. The manufacturer claims, that the new system "Hot Dog" (with combination of under body and upper body warming) is as effective as forced air warming, while not having any disadvantages of the forced air system, like: airborne infection, noise, high power consumption and hard-to-clean hose. The investigators will compare the new Hot Dog patient warming device combination (under body + upper body) with the established warming system, which blows warm air via a mattress over the body of the patients).