Purpose
As the Surgery Encyclopedia explains, the purpose of a heart and lung machine is to allow the body to survive while the heart is stopped. The heart needs to be stopped for some kinds of surgery, including coronary bypass surgery, open heart surgery to repair heart valve damage and surgery to repair other problems in the heart or aorta. The heart and lung machine replaces the normal function of the heart and lungs by pumping blood and oxygenating it so that the body can still have an adequate oxygen supply while the heart is stopped. This kind of treatment allows for oxygen to be added and carbon dioxide to be removed from the blood, while also maintaining temperature control. It can be used for both adult and pediatric patients.
Preparation
As the Heart Surgery Forum explains, the first step in using a heart and lung machine is to block the clotting of blood. This is done by administering heparin, which is a powerful anticoagulant medication. Once the blood cannot clot, a tube is inserted into the right atrium to drain blood and feed it into the heart and lung machine. Another tube is put into the aorta so that oxygenated blood can be pumped back into the body's circulation. Once these steps have been performed, the machine is ready to control the body's circulation, and the patient's heart can be stopped.
Mechanism
Once the heart is stopped, the heart and lung machine is responsible for maintaining circulation throughout the body. Deoxygenated blood (which has a blue color) is drained out of the right atrium. The blood is then pumped into a reservoir, which holds blood. Oxygen is then bubbled into the blood in the reservoir, which turns the blood red as it binds to oxygen and releases the carbon dioxide. The freshly oxygenated blood is then pumped through the rest of the machine and is inserted back into the arteries. The heart and lung machine uses a series of pumps to make sure that blood is able to keep flowing throughout the body. The tube that drains blood from the right atrium is kept under negative pressure, which helps suck all of the blood out of the heart area. Not only does this allow the body to receive oxygen while the heart is stopped, it also keeps blood away from the heart while the surgeon is operating, making it easier for the surgery to be completed.
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