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Posted by on Dec 6, 2016 in Tell Me Why |

What Is an Extracorporeal Membrane Heart Assist Device?

What Is an Extracorporeal Membrane Heart Assist Device?

An extracorporeal medical procedure is one which is performed outside the body. An extracorporeal membrane heart assist device then assists a person whose heart and lungs are unable to produce enough oxygen to stay alive.

Criteria for the initiation of ECMO include acute severe cardiac or pulmonary failure that is potentially reversible and unresponsive to conventional management, according to the Extracorporeal Life Support Organization.

ECMO stands for extracorporeal membrane oxygenation. The ECMO machine is similar to the heart-lung by-pass machine used in open-heart surgery. It pumps and oxygenates a patient’s blood outside the body, allowing the heart and lungs to rest.

When you are connected to an ECMO, blood flows through tubing to an artificial lung in the machine that adds oxygen and takes out carbon dioxide; then the blood is warmed to body temperature and pumped back into your body.

ECMO has the word ‘oxygenation’ in it because the heart assist device removes blood from a person’s body, diminishes carbon dioxide in the blood and pumps oxygen into the red blood cells to infuse life giving blood that helps a person stay alive.

The blood is pumped directly into the body to energize it as the heart and lungs are unable to perform that pumping, life-giving function. While reports vary about survival rates, with acute respiratory failure, the use of ECMO has been shown to improve survival rates, say some scientific papers.

“Survival rates from 50 to 70 percent have been reported in observational and uncontrolled clinical trials,” according to a 2009 scientific paper by Thomas V. Brogan, Ravi R. Thiagarajan, Peter T. Rycus, Robert H. Bartlett and Susan L. Bratton.

There are two types of ECMO. The VA ECMO is connected to both a vein and an artery and is used when there are problems with both the heart and lungs. The VV ECMO is connected to one or more veins, usually near the heart, and is used when the problem is only in the lungs.

When is ECMO used:

For patients recovering from heart failure, or lung failure or heart surgery.

As a bridge option to further treatment, when doctors want to assess the state of other organs such as the kidneys or brain before performing heart or lung surgery.

For support during high-risk procedures in the cardiac catheterization lab.

As a bridge to a heart assist device, such as left ventricular assist device (LVAD).

As a bridge for patients awaiting lung transplant. The ECMO helps keep tissues well oxygenated, which makes the patient a better candidate for transplant.

Procedure

Being placed on ECMO requires a surgical procedure but it is usually done in a patient’s room. The patient is sedated and given pain medication and an anti-coagulant to minimize blood clotting. A surgeon, assisted by an operating room team, inserts the ECMO catheters into either an artery or veins. An x-ray is then taken to ensure the tubes are in the right place. Usually a patient on the ECMO pump will also be on a ventilator, which helps the lungs to heal.

While on ECMO, the patient will be monitored by specially trained nurses and respiratory therapists, as well as the surgeon and surgical team. Since you will be sedated and have a breathing tube in place, supplemental nutrition will be provided either intravenously or though a nasal-gastric tube. Nutrition is delivered either intravenously or though a nasal-gastric tube.

While on ECMO, you may be given certain medications including: heparin to prevent blood clots; antibiotics to prevent infections; sedatives to minimize movement and improve sleep; diuretics to help the kidney get rid of fluids; electrolytes to maintain the proper balance of salts and sugars; and blood products to replace blood loss. Discontinuing ECMO requires a surgical procedure to remove the tubes.

Multiple tests are usually done prior to the discontinuation of ECMO therapy to confirm that your heart and lungs are ready. Once the ECMO cannulas are removed, the vessels will need to be repaired. This can be done either at the bedside or in the operating room. The doctor will use small stitches to close the spot where the tubes were placed. You will be asleep and monitored for this process. Even though you are off the ECMO, you may still need to be on a ventilator.

Risks

ECMO does carry risks including:

Bleeding, due to the medication that’s given to prevent blood from clotting in the tubing.

Infection at the sites where the tubes enter the body.

Transfusion problems, since a person on ECMO is given blood products.

Small clots or air bubbles forming in the tubing.

Increased chance of stroke.

Content for this question contributed by Tom Lacey, resident of McKees Rocks, Allegheny County, western Pennsylvania, USA