Peri-operative active warming has been researched over the past 30 years, with more sophisticated methods of active warming being introduced in recent years. Regardless of their complexity, these devices are used in order to prevent inadvertent perioperative hypothermia (IPH) and its complications in patients who undergo an operation. Complications of IPH include: thermal discomfort (including shivering), increased intra-operative blood loss, increased risk of wound infection, cardiac morbid events and increased length of stay in recovery room and in the hospital.