A Heart-Lung Bypass Machine is a device used to oxygenate and circulate blood in a patient with no heart or lung function, essentially replacing the function of both of those organs. It is used primarily in open-heart surgery, including heart transplants, but may also be used in a patient with no heartbeat when the physician feels that the patient's life may still be saved if a problem with the heart or lungs can be repaired. A patient can be kept alive on bypass for a considerable period of time. However, setting up the machine requires that it be hooked up both to the aorta and the venae cavae. This requires surgery and usually requires the patient to be under anesthetic.