Described are systems and methods of perioperative warming. One method comprises providing a regulated power supply that is controlled by a controller, wherein the regulated power supply provides power to one or more polymer positive temperature coefficient (PTC) heating elements, each PTC heating element having a saturation voltage and a corresponding saturation temperature； applying a first voltage to at least one of the one or more PTC heating elements, wherein the first voltage is greater than the saturation voltage； monitoring a temperature of the one of the one or more PTC heating elements while the first voltage is being applied； and regulating voltage applied to the one of the one or more PTC heating elements as the monitored temperature of the one of the one or more PTC heating elements approaches the saturation temperature of the one of the one or more PTC heating elements.
