A device that temporarily takes over the function of the heart and lungs. It is used in certain operations in the chest, giving the surgeon more time for procedures such as open-heart surgery, heart transplants and heart-lung transplants. The machine also ensures an operating area largely free from blood, which helps the surgeon to work more quickly. A pump replaces the heart and an oxygenator replaces the lungs. When in use, the machine bypasses normal cardiopulmonary activity. It also contains a heat exchanger to warm or cool the patient's blood according to the requirements of the operation. The patient is given an anticoagulant (HEPARIN) to counteract clotting which may occur when blood cells get damaged during the machine's use.