Overview of the Heart Lung (Cardiopulmonary) Bypass Machine In Surgery

What Is Cardiopulmonary Bypass or Heart Lung Bypass?

Pulmonary, lungs, breathing, pulmonary disease
The heart and lungs (shown here) are stopped while a person undergoes bypass surgery, and a machine takes over for them. Image: ADAM

What Is a Cardiopulmonary Bypass Machine (CBM)?

A cardiopulmonary bypass machine (CBM) is commonly known as a heart-lung machine. It is a device that does the work of the heart and lungs when the heart is stopped for a surgical procedure, or for other reasons. Most patients are on the pump only as long as it takes to complete open heart surgery.

Why Is Cardiopulmonary Bypass Used?

To stop the heart without harming the patient, oxygenated blood must continue to circulate through the body during surgery.

The pump does the work of the heart, pumping blood through the body. The machine also oxygenates the blood while pumping, replacing the function of the lungs.

The CBM is used for two primary reasons. The most common reason is so the heart can be stopped for surgery. Many cardiac surgeries would be impossible to perform with the heart beating, as surgery would be performed on a “moving target” or there would be significant blood loss. For other patients, the pump is used not for surgery, but to help out if a patient has heart failure. In some cases, a heart failure patient may be placed on the pump to support the patient until a heart transplant becomes available.

How Does Cardiopulmonary Bypass Work?

The surgeon attaches special tubing to a large blood vessel (like starting a very large IV) that allows oxygen-depleted blood to leave the body and travel to the CBM. There, the machine oxygenates the blood and returns it to the body through a second set of tubing, also attached to the body.

The constant pumping of the machine pushes the oxygenated blood through the body, much like the heart does.

The placement of the tubes is determined by the preference of the surgeon. The tubes must be placed away from the surgical site so they do not interfere with the surgeon’s work, but placed in a blood vessel large enough to accommodate the tubing and the pressure of the pump.

The two tubes insure that blood leaves the body before reaching the heart and returns to the body after the heart, giving the surgeon a still and mostly bloodless area to work.

A third tube is also inserted very near or directly into the heart, but not connected to the CPM. It is used to flush the heart with cardioplegia, a potassium solution which stops the heart. Once the cardioplegia takes effect, the CBM is initiated and takes over the heart and lung function.

Who Runs The Cardiopulmonary Bypass Machine?

The person who runs a cardiopulmonary bypass pump is called a perfusionist. Perfusionists typically have a bachelor’s degree in a health-related field, then pursue an additional two years of education training as a perfusionist. Some perfusionists take an exam to become a certified clinical perfusionist, which is similar to a physician being board certified in a specialty.

The Risks of Cardiopulmonary Bypass

The risks of being on heart and lung bypass include blood clots, bleeding after surgery, surgical injury to the phrenic nerve, acute kidney injury and decreased lung and/or heart function.

 These risks are decreased with shorter times on the pump and increased with longer pump times.  

For More Information About The Human Heart & Heart Surgery

Sources:

Cardiopulmonary Bypass. Cincinnati Children’s Hospital. Accessed April, 2009.

Risk Factors for Pulmonary Complications Following Cardiac Surgery With Cardiopulmonary Bypass .  Accessed May, 2016. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775118/

What Is a Cardiovascular Perfusionist? Perfusion.com. Accessed April, 2009. http://www.perfusion.com/cgi-bin/absolutenm/templates/articledisplay.asp?articleid=1550

What To Expect During Heart Surgery. National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/hs/hs_during.html

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