Extracorporeal Membrane Oxygenation (ECMO)
Extracorporeal Membrane Oxygenation, or ECMO for short, is an advanced therapy that is sometimes used to do the work of the heart and lungs when a patient’s own organs are too sick or weak to work on their own. It is effectively a modified heart-lung bypass machine—a machine that takes over heart and lung function (meaning it adds oxygen to and removes carbon dioxide from a patient’s blood supply).
But unlike a heart-lung bypass machine, which is designed for short-term use (during heart surgery, for instance), ECMO machines provide long-term heart and lung support over a period of hours, days, or even weeks to give a patient’s heart and lungs time to heal and regain function.
ECMO can be used for patients of all ages, from infants to adults. It can help patients with a range of severe heart and lung conditions, from cardiac arrest to respiratory failure. But in most cases, ECMO therapy is used only when all other conventional treatments have failed to resolve the underlying heart or lung disorders.
“ECMO is really the most advanced supportive therapy that is available to critically ill patients suffering from acute or chronic cardiac and respiratory failure,” says Arnar Geirsson, MD, Yale Medicine’s section chief of cardiac surgery. “Not everyone is a candidate for ECMO, but it can be life-saving, if initiated in a safe and expeditious manner.”
What is ECMO?
ECMO is a therapy used to treat people with life-threatening heart and lung failure. ECMO involves the use a machine to replace some of the functions of a patient’s lungs or heart, or both simultaneously. While ECMO therapy can be life-saving, it is not itself a treatment. Instead, it provides a kind of bridge, a temporarily replacement that keeps the functions of the heart and lungs going while doctors treat the underlying problem.
For instance, a patient whose lungs do not provide adequate oxygen to the body, even when given oxygen, may be a candidate for ECMO. Alternatively, a doctor may recommend ECMO therapy for a patient whose lungs fail to clear carbon dioxide in spite of the use of a mechanical ventilator, or for a patient whose heart cannot pump enough blood around the body even with the application of conventional treatments for the underlying condition.
In other words, ECMO therapy is frequently a treatment of last resort. It is recommended when other treatments have failed to resolve the underlying problem, but there is still a possibility of recovery.
How does ECMO work?
Connecting a patient to the ECMO machine requires surgery. The ECMO machine connects to a patient through plastic tubes called cannulas. After giving the patient an anticoagulant, a medication that prevents blood from clotting, the doctor inserts cannulas into large arteries and veins located in the chest, neck, or legs.
Once connected, the ECMO machine draws blood from the patient, which it then passes through the cannulas and into an artificial lung that infuses the blood with oxygen and removes carbon dioxide. The ECMO machine then warms this treated blood to body temperature and pumps it back into the patient. In cases where a patient’s heart cannot circulate blood on its own, a mechanical pump takes over the heart’s role and pumps blood through the patient’s circulatory system.
After the procedure, doctors continue to administer sedatives and pain medications to keep patients as comfortable and pain-free as possible. An ECMO team of doctors, nurses, and other health care providers will perform routine chest X-rays that allow doctors to evaluate and track the patient’s lung and heart health. The team will also run regular blood tests to assess oxygen and carbon dioxide levels and to check for possible infections.
What conditions is ECMO used to treat?
While there is no fixed list of conditions for which ECMO is used, doctors may recommend its use in the following situations:
- Respiratory failure (when the lungs fail to maintain adequate oxygen levels or remove enough carbon dioxide from the blood)
- Heart transplantation
- Lung transplantation
- Cardiac arrest (when the heart fails to pump blood effectively)
- Cardiogenic shock (when the ventricles of the heart do not function properly, resulting in insufficient blood flow)
- Pulmonary embolism (when an artery in the lungs is blocked)
- Birth defects of the heart
- Acute Respiratory Distress Syndrome, ARDS (a type of respiratory failure that prevents adequate oxygen from getting to the lungs and blood)
Why Is ECMO used in some COVID-19 Patients?
Some people severely affected by COVID-19 develop a life-threatening lung condition called acute respiratory distress syndrome, or ARDS for short. People with ARDS struggle to get enough oxygen into their lungs and blood due to a buildup of fluid in air sacs called alveoli. Some COVID-19 patients with ARDS who do not respond to conventional treatment may benefit from ECMO therapy.
When does a patient “come off” ECMO?
In general, doctors aim to take patients off ECMO therapy as quickly as possible. Because it is used for patients with a range of conditions, each with its own recovery timetable, the length of time someone is on ECMO therapy can vary greatly. Some patients need it for only a few hours while others may require days or weeks of ECMO support.
Once the patient reaches a point at which the ECMO machine is no longer necessary, the ECMO team will begin the process of weaning.
This does not mean that the ECMO machine will be turned off. Rather, the team performs a trial, sometimes called a weaning trial, in which they steadily decrease the patient’s blood flow through the machine.
Over several hours, they track the patient’s response to this reduction in ECMO support. If the patient responds well, and the ECMO team concludes that discontinuation of ECMO is safe, a surgeon will remove the cannulas. (The cannula sites will be stitched closed after this procedure.)
After coming off ECMO, a patient might require a ventilator to provide breathing support. As soon as the patient is able to breathe without assistance, doctors will remove the ventilator. But patients may still need to stay in the hospital for days or weeks, at least until vital signs are stable. Many will also need physical therapy to help regain muscle strength, as well as speech therapy to aid recovery after long-term use of a ventilator’s breathing tube.
Even with excellent care and ECMO therapy, sometimes the underlying heart or lung condition does not get better. If the ECMO team believes that a patient will not recover, even if ECMO therapy is prolonged, they will discuss end-of-life options and removal of ECMO support with family members.
What are the risks associated with ECMO?
Because people who are recommended for ECMO therapy are very sick, they are already at high risk of complications, including death. ECMO therapy itself comes with its own set of risks including:
- Bleeding: Bleeding affects up to 50% of ECMO patients and, in some cases, can be life-threatening. ECMO therapy requires the use of anticoagulants, medications that thin the blood (and prevent the formation of clots) to keep the blood flowing through the body and ECMO machine. But these medications also increase the likelihood of excess bleeding. As a result, hemorrhaging may occur in a number of places, including the lungs, stomach, mouth, nose, and brain. Doctors watch for signs of bleeding; medication or surgery may be necessary to stop it.
- Kidney Failure: In some cases, patients on ECMO do not circulate enough blood to their kidneys, resulting in kidney failure and the potential need for dialysis, a machine that does some of the work normally done by kidneys. Kidney function usually returns after the patient is removed from the ECMO machine, though sometimes the kidneys do not recover, and the patient will require lifelong dialysis treatment.
- Bacterial Infection: Because cannulas are inserted into veins and arteries in ECMO therapy, bacteria can have direct access to the patient’s blood stream. If unchecked, infections may result, such as bacterial pneumonia. If infection is suspected, patients are treated with a course of antibiotics and cannulas may be replaced.
- Stroke: In rare cases, ECMO patients develop small blood clots that can reduce the flow of blood to the brain. This raises risk for stroke.
- Pulmonary Embolism: Though it is rare, some patients on ECMO develop a blood clot that blocks blood flow in the lungs. Pulmonary embolism can cause permanent damage to the lungs, as well as damage to other organs as the lungs may be unable to provide enough oxygen to the body.
What stands out about Yale Medicine’s approach to ECMO?
At Yale Medicine, our neonatal, pediatric, and adult critical care specialists are trained in the use of ECMO and other aspects of intensive care. Our physicians and nurses are up to date on current practices and research about the use of ECMO.
“We have a multidisciplinary team of highly qualified physicians from cardiac surgery, critical care, heart failure cardiology, and pulmonary critical care that work together to make sure every patient is offered the most advanced and effective treatment possible,” says Dr. Geirrson.