To repair most cardiac defects, the surgeon (a doctor who operates on the heart and lungs) needs a bloodless, motionless surgical area. To do this, the motion of the heart and lungs must be stopped.

Cardiopulmonary bypass (CPB) is the process that allows blood, oxygen, and nutrients to circulate throughout the body while the heart and lungs don’t move.

Large catheters (tubes) called cannulas are placed in the right side of the heart. This moves blood from the body through a tube. Next, this blood from the body enters the cardiopulmonary bypass circuit. This circuit has a mechanical pump that can be set to the proper cardiac output, or blood flow, for a patient. After running through the pump, the blood continues to the oxygenator.

The oxygenator does the same job as the lungs. It oxygenates the blood and removes carbon dioxide.

This re-oxygenated blood is returned to the body by another cannula placed in the aorta (the main artery of the body).

In this way, cardiopulmonary bypass allows the patients' blood to bypass the heart and lungs. This helps the surgical area stay still and not have blood in the way. It continues to supply blood to the other organs of the body.

This machine is called the heart-lung machine or the pump.

When a patient is being supported by a heart-lung machine, the patient is said to be "on bypass" or "on the pump."

When a patient is taken off this support, it is called "off bypass" or "off the pump."

Cardiopulmonary Bypass Risks

There are risks to using Cardiopulmonary bypass. All organ systems are affected by cardiopulmonary bypass. These effects can be mild to severe based on how sick the patient is before surgery, the length of time that a patient is supported by CPB, and how complex the surgery is.

Side effects can impact the heart or brain during and after surgery. The chance of stroke or seizures during or after bypass is low.

The kidneys may have damage, ranging from lower amounts of pee to kidney failure.

Areas of the lung may not fully expand after bypass. This condition is known as atelectasis.

During CPB, the patients' blood is in contact with foreign surfaces that make up the heart-lung machine. This leads to a reaction by the patient's body. This can cause swelling of different body parts, fever, and abnormal blood tests. This response could be damaging to certain tissues in the body. We try to minimize this response with medicine before and during surgery.

Because extra fluid is needed to fill the cardiopulmonary bypass circuit, the patients' blood volume is diluted. The patient may need a blood transfusion to help with this. .Blood clotting abnormalities will be watched after surgery.

The risk of serious complications related to cardiopulmonary support depends on the age of the patient, how sick they are at the time of the surgery and how complex surgery is.

In most cases this risk is below one percent. In higher, more-complex situations, the risk may be 10 percent to 20 percent.

Who Operates the Heart-Lung Machine During Surgery?

The CPB machine is run by a “perfusionist” who is a member of the open-heart surgical team.

The cardiovascular perfusionist will put together the proper circuit for the patient based on their body size and the surgery type.

Cardiovascular perfusionists on staff at Cincinnati Children's Hospital Medical Center are board-certified by the American Board of Cardiovascular Perfusion.

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