Extracorporeal Membrane Oxygenation in Adults (ECMO)

Overview of Extracorporeal Membrane Oxygenation in Adults

Extracorporeal membrane oxygenation (ECMO) is a life-saving technology that helps critically ill adults and children by performing the functions of the heart and lungs when these organs aren’t working effectively, even after usual treatments or CPR (a procedure to help a patient whose heart has stopped beating). An ECMO machine acts as a pump with an oxygenator, taking over the job of the heart and lungs and buying these organs vital time to recover.

According to a group called the Extracorporeal Life Support Organization, ECMO has been used to treat 151,683 patients as of 2020, including newborns, children, and adults. The use of ECMO has expanded greatly over the years, from 83 centers in 1990 to 492 centers in 2020. There are two types of ECMO treatment: veno-venous ECMO (VV ECMO) to help with breathing, and veno-arterial ECMO (VA ECMO) to help both heart and lungs.

The idea of ECMO came from studies in the 1940s where blood was oxygenated through artificial kidneys. This inspired the creation of the first successful open-heart operation in 1953. There were two early types of systems used: a film oxygenator where blood was passed through several discs, and a bubble oxygenator where oxygen was bubbled through deoxygenated blood.

These early devices had several drawbacks including damage to blood cells and blood clotting. In 1956, a new device that was safer for heart surgeries was invented and the first ECMO treatment for babies with breathing problems happened in 1965. Over the years, many changes were made to the designs of these devices, to improve their function and safety.

Unlike treatments that modify disease, ECMO is a supportive therapy. Modern oxygenators used in ECMO circuits are made of polymethylpentene, a type of plastic, and they are durable, efficient, and cause less damage to blood.

ECMO has had a significant impact on survival rates, especially for patients with severe breathing problems. For instance, in 1981, the first successful use of ECMO in a large group of patients with acute respiratory distress syndrome (a serious lung condition that causes low oxygen levels in the blood) was demonstrated.

Even though its benefits were not always clear in the past, a landmark trial in 2009 showed significant advantages of ECMO over standard treatment in reducing death and disabling conditions, highlighting its critical role in severe respiratory failure. Since then, ECMO has been increasingly used to save lives.

Anatomy and Physiology of Extracorporeal Membrane Oxygenation in Adults

Extracorporeal membrane oxygenation, or ECMO, is a procedure where your blood is taken out of your body, cleaned, and then put back in. This is done through a machine connected to a tube (or catheter) inserted into your veins or arteries. This machine works like an artificial lung, removing carbon dioxide and adding oxygen to your blood.

To understand this better, remember that in normal conditions, our blood carries oxygen from our lungs to different parts of the body. However, when our lungs are not working properly, the ECMO machine takes over this job. So, the blood with a lower oxygen level and a higher carbon dioxide level is taken out of the body and is passed through a component called an oxygenator. This oxygenator works just like our lungs; it adds oxygen and removes carbon dioxide from our blood. The cleansed, oxygen-rich blood is then returned back to the body.

There are two types of ECMO, called VV ECMO and VA ECMO. VV ECMO only helps with breathing issues, and VA ECMO helps when both the heart and lungs are struggling. VA ECMO can be used when the heart is too weak to pump the blood effectively or when someone has had a cardiac arrest that other treatments have not helped.

Veno-Venous (VV) ECMO uses a single or double venous cannula, which are tubes inserted into your blood vessels. The single venous cannula extracts blood and returns it through the same tube, which requires careful placement and monitoring. This type of cannula allows patients to move around easier since it’s only placed in one location on the neck. But, it can also cause some issues like shifting with the patient’s movement and interference with the blood flow. Meanwhile, the double venous cannula uses two separate tubes, minimizing the chances of mixing oxygenated blood with deoxygenated blood. However, their placement in two different sites means the patient won’t be able to move around as much.

Veno-Arterial (VA) ECMO uses different types of cannulas depending on the patient’s condition and the body regions the catheter will enter and exit. Some of them drain blood from the right atrium or vena cava and infuse it back into the thigh, shoulder, or neck arteries. This type of ECMO can support the heart and lungs together and can be an option when femoral artery access is not possible due to underlying vascular disease. The right common carotid artery or axillary artery may be used instead.

Why do People Need Extracorporeal Membrane Oxygenation in Adults

Extracorporeal Cardiopulmonary Resuscitation, or ECPR, involves the use of a machine to take over the work of the heart and lungs during a cardiac arrest. There are specific requirements for someone to receive this treatment:

1. They have to be less than 70 years old
2. The time between when their heart stops and when CPR is started has to be less than 5 minutes
3. Their heart failure has to have been seen by someone
4. Their heart’s initial rhythm should show certain types of abnormal beating
5. If their heart starts and then stops again, or starts for a short time
6. They should not have other serious health problems like severe heart failure, lung disease, liver failure, kidney failure, or untreatable conditions
7. They do not have a leaky aortic valve, which is a heart valve issue

ECMO machines are also used for longer periods in intensive care units, where they can support the body’s functions while doctors treat underlying problems.

VA ECMO is used when both the heart and lungs need help. This can be for a variety of reasons – including low heart output, low blood pressure, or shock due to a heart attack, irregular heartbeat, infection affecting the heart, heart muscle inflammation, blocked blood flow to the lungs, medication overdose, heart injury, or severe allergic reaction. VA ECMO can also support the heart during high-risk procedures, after surgery, and after a heart or lung transplant.

VV ECMO is used when the lungs need support. This can be necessary in patients whose lungs are not responding to a breathing machine or any reversible lung failure, such as severe lung disease from bacterial or viral infections (including COVID-19), blockage of the airway, smoke inhalation, drowning, lung bleeding, or severe asthma. This treatment can help maintain the oxygen and carbon dioxide levels in the body until the lungs recover, and it can also be used to help patients who are waiting for a lung transplant or lung resection, which is surgery to remove part of the lung.

When a Person Should Avoid Extracorporeal Membrane Oxygenation in Adults

There are certain situations where a doctor cannot use particular medical treatments. Here are some specific details:

A treatment may be completely ruled out, or ‘absolutely contraindicated’, in the following cases:

• If a cardiac arrest happens when no one is around to witness it,
• If CPR has been performed for a long time without any signs of improved circulation,
• If a patient can’t be considered for transplant or Ventricular Assist Device (VAD) support, which is a device that helps pump blood from the heart to the rest of the body,
• If the patient has a tear in the large blood vessel leading from the heart which hasn’t been repaired, called an aortic dissection,
• If the patient has severe aortic regurgitation, which means that the blood in the heart is flowing backwards,
• If the patient has a severe brain injury that can’t be reversed,
• If the patient has cancer throughout many parts of their body.
• If a patient has a severe dysfunction in an organ such as the lungs (emphysema), liver (cirrhosis), or kidneys (renal failure),
• If the patient has peripheral vascular disease, which is a circulation disorder that affects blood vessels outside of the heart and brain, it can make peripheral VA ECMO risky. This treatment uses a machine to replace the work of your lungs and/or heart,
• If the patient has certain deadly genetic disorders,
• If the patient has pulmonary hypertension or their heart is failing to pump blood (cardiogenic failure), a treatment called VV ECMO is not suitable. This is similar to VA ECMO, but specifically helps with lung functionality.

Meanwhile, some situations, or ‘relative contraindications’, might make the doctor reconsider using a treatment, but don’t fully rule it out. These include cases such as:

• Obesity,
• Advancing age,
• A pre-existing illness that has a poor long-term prognosis, meaning it’s expected to get worse over time,
• If a patient has needed a machine to breathe for them for over 14 days.

Equipment used for Extracorporeal Membrane Oxygenation in Adults

Veno-venous (VV) and Veno-arterial (VA) ECMO are both types of life support but they have some differences. ECMO stands for extracorporeal membrane oxygenation, a procedure that uses a machine to take over the work of the lungs and sometimes the heart. The VV method requires a tube (cannula) to be inserted into a vein while the VA method needs tubes to be placed in both an artery and a vein.

VV ECMO mainly targets the lungs, helping to improve oxygen levels in the blood while VA ECMO gives support to both the lungs and the heart. VV ECMO typically needs a higher rate of blood flow and runs a lower risk of complications compared to VA ECMO. The systems used in these methods are connected differently to the heart and lungs which affects how they work.

The ECMO uses something called a pump, which propels blood through the device. There are two types used: The centrifugal pump which contains plastic parts that spin at high speed to push the blood forward, and the roller pump which uses rollers to squeeze a tube and so move the blood. Each type of pump has its advantages and disadvantages – for example, the centrifugal pump is portable but more expensive, while the roller pump is cheaper but could present a risk of tube rupture if not used properly.

The oxygenator, a part of the ECMO machine, is a device that acts a bit like your lungs. It adds oxygen to the blood and removes carbon dioxide. There are different types, for example, microporous polypropylene hollow fiber oxygenators are often used and are quite effective. They work well and are preferred because they need smaller volume, provide better gas exchange and resist better to blood flow.

The ECMO machine utilizes specially designed tubes and connectors to transport blood. The size of the tubing depends on the patient’s needs. The tubes are usually made of polyvinyl because it’s flexible, smooth, transparent, and more resistant to common problems like kinking and collapsing. Where the tubes are placed in the body (cannulation) can also differ and depends on the specific patient requirement. It can either be central, through the chest, or peripheral, through the leg or neck.

For the ECMO machine to work properly, it’s important to prevent blood from clotting inside the machine. This is managed by regular and careful monitoring and administration of anticoagulation medicines, the most common of which is heparin. Balancing the prevention of blood clotting with the need to allow normal blood clotting to prevent bleedings is essential.

Who is needed to perform Extracorporeal Membrane Oxygenation in Adults?

The ECMO team is a group of different healthcare professionals who work together to take care of your health. This team includes a heart surgeon or an interventional cardiologist (a doctor who treats heart problems without surgery), who are responsible for inserting the tubes that the ECMO machine needs to work. The team also includes an intensivist (a doctor who specializes in the care of critically ill patients), a perfusionist (a specialist responsible for managing the heart-lung machine), an ECMO specialist, a respiratory therapist (a health worker who helps treat lung conditions), and a nurse to be by your bedside.

An ECMO specialist is a high-level expert trained to manage the ECMO machine as per your specific health conditions. They do this under the advice and watch of a doctor who has special training in using the ECMO machine.

Preparing for Extracorporeal Membrane Oxygenation in Adults

Here is a simplified explanation of the process of preparing for a medical procedure involving the use of a cannula, a thin tube that can deliver or remove fluids or gases from the body. This process is performed in several steps.

The first step is the insertion of the cannula. The cannula is then connected to a circuit system. Making sure no air remains in the circuit is critical. The next step is inspecting for any gases and removing any air bubbles that may be present in the circuit, membrane, or any other connected parts.

After that, the medical team will connect a gas flow, typically oxygen, to the device and set it at a specific rate. The rate of the rotations per minute (RPM) in the system is then increased to create enough pressure. The clamps on the circuit, if any, are removed, resulting in the forward flow of blood. The RPM is further increased to achieve the desired blood flow rate. Finally, if the patient was having chest compressions, these are stopped.

Now, depending on the medical situation, the position of the cannula is confirmed using imaging techniques, like fluoroscopy or echocardiography which are ways to look inside the body without making incisions. Certain drugs may also be used to maintain the proper functioning of the patient’s organs. A series of other preparatory measures including endotracheal tube placement (a tube down the windpipe), ultrasound scans, and blood tests are also performed.

It’s important to start the procedure soon after unsuccessful attempts at resuscitation, ideally within 10 to 20 minutes. Delaying it increases the risk of damage to the brain and other organs due to low oxygen levels. The aim is to establish blood flow within one hour of cardiac arrest. If the procedure cannot be performed at the current facility, the patient should be transported to the nearest appropriate center as soon as possible. Until that can happen, high-quality CPR must continue without interruptions.

Lastly, the procedure involves sterilizing the femoral area, which is near the thigh, and performing cannulation. If chest compressions are needed, an automated device is used for this. This crucial step is performed by a highly trained team that may include surgeons, cardiologists, and emergency room doctors.

How is Extracorporeal Membrane Oxygenation in Adults performed

Traditional ECMO (Extracorporeal Membrane Oxygenation) Circuits are specialized medical equipment used to support the heart and lung functions. These machines are often used when a patient’s heart or lungs are unable to properly function on their own. There are essentially three types of circuits: Veno-Venous (VV) ECMO, Peripheral Veno-Arterial (VA) ECMO, and Central Veno-Arterial (VA) ECMO.

Veno-Venous (VV) ECMO handles only blood from the veins, and it is typically used when only lung function is compromised. There are different setups for how these tubes (cannulas) are placed in the body – some would go from the thigh vein to the heart, while others might have a single tube inserted into a vein in the neck. Each method has different specifics and the doctors will choose what’s most suitable for each patient.

Peripheral and Central Veno-Arterial (VA) ECMO both deal with the arterial system, meaning they tend to provide more support to the heart. The placement of these tubes can vary, either in the same groin or different ones, with their own benefits and precautions. If the inserted tubes cause complications (like pain and swelling), the doctors might need to change the ECMO configuration.

Besides these traditional setups, there are also some hybrid ECMO circuits, which are modified to cover more specific needs. For example, sometimes an additional tube may be added to a VV ECMO set up, in order to provide further oxygenation if the patient’s condition worsens. Parallel circuits, which run two ECMO systems at once, can also be used when more advanced help is needed, although they are said to have lower survival rates compared to the traditional ones.

Once the ECMO circuit is set up, it needs careful monitoring and adjustments to ensure the correct blood flow and conditions are met. Moreover, the medical team will pay close attention to avoid potential complications, such as bleeding, heart problems, or lung congestion. They also have to manage the equipment settings, including oxygen and air blend, body temperature, and more, striving for the best support for the patient.

In summary, ECMO machines and their circuits are a paramount tool in supporting patients with dysfunctioning heart or lungs. And while the process might seem complicated, patients should rest assured knowing that every decision and adjustment is being closely managed by the healthcare professionals.

Possible Complications of Extracorporeal Membrane Oxygenation in Adults

Bleeding is a serious and potentially life-threatening event that can happen after a certain medical procedure known as ECMO (Extracorporeal Membrane Oxygenation). This can lead to severe and dangerous bleeding in areas such as the brain, lungs, or stomach. Reasons for this bleeding could be tied to various medical conditions or medications, such as the use of blood thinners, or problems with clotting caused by kidney or liver disease. Shortly after the procedure begins, one might see changes in blood clotting.

Unfortunately, bleeding is a common problem after ECMO. So medical professionals, including the patient’s doctors and nurses, will keep a close eye to catch any signs early. They may reduce some medications or give platelet transfusions to stop the bleeding. But while these treatments can help, patients also need to be aware of the risk of blood clotting, which can be fatal.

To lower risks related to this, invasive or surgical procedures should be kept to a minimum whenever possible. Health care providers will keep a close eye on their patients’ blood platelet count and clotting time, and may adjust medication as needed.

Bleeding in the lungs can be controlled with drugs or an examination of the with a scope, known as bronchoscopy. Between 10 to 15% of patients with a lung condition known as ARDS who undergo ECMO, experience a brain bleed or a blockage. This actually accounts for nearly half of all deaths related to ECMO. High levels of a protein known as plasma-free hemoglobin in the blood may indicate a common condition known as hemolysis. Thus, regular checks are highly recommended.

Other potential complications include blood clots in the heart that can form due to the alterations of blood flow during the procedure, air bubbles in the blood vessels (also known as gas embolism), clotting in the ECMO circuit, a rare side effect of a popular blood thinner known as Heparin called Heparin-induced Thrombocytopenia (HIT), seizures or other brain complications, failure of the kidneys leading to less urine, gastrointestinal complications such as bleeding in the stomach, severe infection, metabolic imbalances such as electrolyte disturbance, problems related to ECMO tube insertion, insufficient oxygen supply to the body’s tissues known as hypoxia, and a drop in blood pressure known as hypotension.

The use of ECMO can also lead to other complications such as the need for putting a breathing tube back in or other complications. It’s important to understand that this is a complex procedure, so all of these problems may be less or more likely based on each person’s unique health condition.

What Else Should I Know About Extracorporeal Membrane Oxygenation in Adults?

ECMO, or Extracorporeal Membrane Oxygenation, is a treatment used for severe heart or lung conditions in adults. It’s often used when traditional treatments, like a heart pump (ventricular assist device), is not effective. ECMO might be considered when a patient’s heart strength (cardiac index) is reduced, when the blood pressure drops below a certain level, and when lactic acid levels surge despite other treatments. ECMO can also be a temporary measure until a heart transplant or getting a ventricular assisted device for patients with an untreatable heart condition.

Apart from heart conditions, ECMO can also be useful for life-threatening but recoverable lung failure. It works by mimicking the natural function of the heart and lungs, allowing the body to rest and heal. However, it’s worth noting that the process could cause inflammation and potential lung damage due to the reaction between the blood and the machine surface.

Studies have shown encouraging results with ECMO treatment. For example, in cases of Acute Respiratory Distress Syndrome (a type of severe lung condition), around 67% of patients could be weaned off ECMO successfully, with 52% surviving until hospital discharge. Among those patients with H1N1 influenza and this syndrome, around 23.7% died while on ECMO, compared to 52.5% who were not on ECMO.

The procedure also has positive outcomes in cases of cardiac arrest, severe heart failure, or difficulty weaning from heart-lung machine use after heart surgery, with a survival rate of 20 to 30%. Patients using ECMO after a cardiac arrest showed more improved survival rates and less neurological damage compared to traditional life-saving methods.

However, ECMO might not always work. If a patient’s organ functioning continues to decline despite ECMO support, it might be best to stop ECMO treatment and consider end-of-life care options. The cost of an ECMO procedure and the total hospital cost could be quite high, but these would depend on individual cases and healthcare plans.