ECMO
There is a possibility that your child may need to be placed on ECMO, extracorporeal membrane oxygenation. Simply put, ECMO allows the heart and lungs to rest as the machine does all or part of the work for the body. Older children and adults can also be placed on ECMO but it is most commonly used on infants.
ECMO is a very serious thing. The statistics that we were given were that only 1 in 3 ever successfully come off of ECMO. If your CDH child does not require ECMO, their chance of survival is around 75-80%. If they do need ECMO support, the chance of survival drops to 33%.
ECMO was developed by Dr. Robert Bartlett when he wondered if a heart/lung machine could be used for days or weeks at a time to improve survival rates after surgery (1).
There are certain conditions that need to be met before deciding on ECMO therapy. There is a weight limit—the baby must weigh a certain amount in order to be considered (4 and a half pounds (2)). Also taken into account is whether or not it is believed that the child will have a good chance of survival with ECMO. That sounds cruel but ECMO therapy is very expensive and potentially dangerous.
There are risks associated with ECMO that will be explained to you prior to placement on the machine. The baby will be receiving blood products. Although blood is carefully screened for HIV and/or other disease/infection, there is a small risk of receiving contaminated blood. There is also a risk of infection as there is with any surgical procedure. The blood thinning medication that the child will be on is another risk (more below) as is renal failure.
The ECMO machine works by acting as a heart/lung bypass. It has a “lung” that oxygenates the blood entering the body and removes carbon dioxide from the blood leaving the body. Your child will have to receive blood and blood products while on ECMO. They will be on a blood thinning medication called heparin. There are risks associated with prolonged usage of heparin including brain bleeds. Because of this very real risk, your baby will probably receive frequent head ultrasounds. Heart echocardiograms (ultrasounds) will also be necessary to monitor how the heart is functioning.
Because of the extra blood needed while on ECMO, extreme swelling is not unusual. There are ways to help reduce the edema including the hemofilter on the ECMO machine, lasix and other medications.
There are actually two types of ECMO, veno-venous (VV) and veno-arterial (VA).
With VA ECMO, there are always two cannulae inserted and there is support for both the heart and the lungs. Blood is removed via a vein and returned to the body via an artery. This is used when heart function is a concern along with lung function. When it is decided that the child will be taken off of ECMO support, “trial-offs” are done. This is where the ventilator is turned up and the cannulae are clamped off for a period of time (3).
Conversely, with VV ECMO, only respiratory (lung) support is provided. Blood is removed via a vein and returned to the body via another vein. The carotid artery is not tied off with this type of ECMO (4). Trial-offs are not done with this type of ECMO; the pump and oxygen level are turned down as low as possible to determine whether or not the child can come off of ECMO. There are cases of a child starting out on VV ECMO and having to be switched to VA ECMO.
Your child will be sedated in preparation for the surgery required to connect them to ECMO. An incision is made in the neck and the first cannula is inserted into the right side of the heart via a vein in the neck. If it is determined that your child requires VA ECMO, the second cannula is then inserted through an artery in the neck. If VV ECMO is utilized, the second cannula is either in the vein or only one cannula with two separate lumen is used (5).
The first cannula carries blood high in carbon dioxide and low in oxygen out of the body and through the ECMO machine (circuit). The second cannula carries blood oxygenated by the ECMO machine back to the heart to circulate throughout the body (5).
The procedure described above is the most common way to place a patient on ECMO. The cannulas can also be inserted directly into the heart via the chest if the blood vessels in the neck cannot be used for some reason of if the child is placed on ECMO while already in surgery.
Additionally, there is a procedure known as exit-to-ECMO where the child is connected to the ECMO machine while still partially in the womb.
Two thick tubes extend out of the neck or chest incision. Each one is approximately the diameter of a dime. These tubes may be stitched to the side of the child’s head to keep them in place. The bed will be raised fairly high because gravity is used to remove the blood to be oxygenated. You will notice that the oxygenated blood is bright red while the non-oxygenated blood is a deeper crimson color.
The child will be able to be awake and move while on ECMO if the doctors do not need them to be paralyzed for any reason. They will remain sedated to help with any discomfort from the cannulas resting in the heart and any other tubes, wires, etc. they have attached to them.
Your child is attached to a man made machine and as with all machines that run 24 hours a day, 7 days a week, mechanical failures are to be expected. The medical staff is specifically trained to deal with and fix these failures. The machine may need to be switched out, there may be a clot in the filter, the circuit may need to be primed, any number of issues can arise. Expect it and do not be surprised when something mechanical fails.
The length of time that can be safely spent on ECMO is not certain. Each facility has their own guidelines. It can range anywhere from 2-8 weeks, sometimes longer. Generally, if no improvement is seen within 2-3 weeks, the advice is to discontinue its use because the risks of prolonged usage of ECMO begin to outweigh the benefits.
Do not expect to see immediate improvement when placed on ECMO. It will usually take up to 10 days to see the benefits.
When it is decided that your child is ready to come off of ECMO, there are two courses of action that can be taken. The first is to sedate the child and perform another surgical procedure to remove the cannulas from the heart via the neck. The neck incision is then stitched closed. The second option is to cut the tubes going to the machine leaving the cannulas in the heart. This may be done for a variety of reasons, including the possibility of a return to ECMO or the surgical schedule is too full to get an entire surgical team in to decannulate.
The possibility of a return to ECMO is generally slim. The arteries and veins in the neck can only withstand so much as can the rest of the body. If no improvement was shown on the first go on ECMO, chances are not good for any subsequent ECMO treatment.
Because ECMO is a relatively new procedure, long-term effects of being on it are not really known. When someone who has been on ECMO as an infant reaches middle age, problems may arise, there is just no study on that as of yet.
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References
1) Famed surgeon retires from U-M...
2) Extracorporeal Membrane Oxygenation