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Extracorporeal Membrane Oxygenation

ECMOI have heard of this system being used successfully to keep a baby or young child alive long enough for a donor to be found, sadly though there is a time limit as to how long a person can survive on one of these machines while waiting for a possible donor.

ECMO uses a heart-lung machine similar to the one in open-heart surgery. There are two types of ECMO your child may use. Venoarterial (VA) ECMO uses an artery and a vein, venovenous (VV) ECMO uses one or two veins. The doctor decides which type your child needs. When a child goes on ECMO, the following things happen:

The child is given medications to prevent pain and movement during the surgery. The surgery will happen in the Intensive Care Unit (ICU), not the Operating Room.

A pediatric surgeon places tubes, or cannulas, into large veins and/or arteries located on the right side of the neck or in the groin. The number of tubes used depends on the type of ECMO your child needs. These vessels are called the internal jugular vein, the carotid artery, the femoral vein and the cephalad vein. Your child may have one special cannula placed into the internal jugular vein, depending on how big your child is. This cannula will do the job of the two cannulas.

The ECMO machine is made up of several parts: a pump, an artificial lung, a blood warmer and an arterial filter. The ECMO machine takes the blue blood (without oxygen) out of the right side of the heart and pumps it through the artificial lung (oxygenator). The blood is now red blood (with oxygen). This blood is warmed and filtered before returning to the child.

The ECMO machine does the work for your child’s heart and/or lungs and allows them extra time while a possible donor is found. The ECMO machine does most of the work for the child’s heart and lungs and even though your child looks much better, it is important to remember that the ECMO machine is doing the work the heart and/or lungs can’t do.

While your child is on ECMO he receives a medicine called heparin. Heparin keeps your child’s blood from clotting in the ECMO circuit. Heparin may cause your child to bleed while on ECMO. Special blood tests, (ACTs) are done every hour to check how fast the blood is clotting. When your child is taken off ECMO the heparin is stopped, and the time it takes your child’s blood to clot will return to normal in a few hours.

Children and some infants may be able to stay on ECMO for a few weeks, but sadly over a period of time there other organ do suffer and then a heart and/or lung transplant would not be possible


Figure 1: Typical ECLS Circuit with venovenous cannulation. Blood drains from the right atrium to the pump, and returns to the patient. The important monitors are shown in boxes.

A diagram of the circuit commonly used for ECLS is shown in Figure 1. The right atrium is cannulated through a large vein, usually the right internal jugular vein. Venous blood drains out of the right atrium, usually aspirated by a simple siphon. Blood passes directly to a self-regulating pump; unlike CPB for cardiac surgery there is no venous reservoir. Blood is pumped through a membrane lung where oxygen, CO2, and water vapor are transferred. This device is commonly referred to as the "oxygenator", although removal of CO2 is even more important than oxygenation for purposes of pulmonary support. The "arterialized" blood returns to the patient. If the application is purely for respiratory support, the arterialized blood is usually returned to the venous circulation, placing the membrane lung in series with the patient's native lungs. This is the application shown in Fig. 1. If the application requires cardiac support blood is returned to the arterial circulation through a catheter in a large artery, usually the right common carotid. In this application the pump and membrane lung are placed in parallel with the native heart and lungs.

Once the ECLS circuit is attached and functioning, blood flow through the circuit is regulated to provide part or all of the circulation and gas exchange. Total cardiopulmonary support is possible by extracorporeal circulation using only part of the venous blood arriving in the right atrium from the systemic circulation. Therefore ECLS is almost always "partial" bypass as opposed to "total" bypass which is required for cardiac operations. With circulation and gas exchange supported mechanically, the native heart and lungs are not needed for life support and are allowed to "rest". This means that ventilator settings and inotropic drugs are decreased to safe, low levels.

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