Overview of Extracorporeal Membrane Oxygenation Weaning
Extracorporeal life support (ECLS), or as it’s often referred to, extracorporeal membrane oxygenation (ECMO), acts like a heart and lung machine for a patient whose own body isn’t working properly. ECMO can be used in various medical conditions and might require two types of support: either venovenous (VV) or venoarterial (VA). The purpose of ECMO is to either help the patient get through their illness or give them time to get a long-term device or transplant.
For a long time, ECMO has been considered an option. But only recently has the medical team really gotten the hang of how to use and administer this life-sustaining machine properly. Managing ECMO involves a large, highly organized team that can perform cannulation (inserting a tube into a patient), manage the ECMO machine, help wean the patient off ECMO, decannulate (remove the tube from the patient), and handle any possible complication that might pop up. This article specifically looks at how to wean adult and pediatric patients off ECMO.
Anatomy and Physiology of Extracorporeal Membrane Oxygenation Weaning
The process of providing a patient with external support for heart and lung function involves a technique called Extracorporeal Membrane Oxygenation (ECMO). There are two types of ECMO – one for lungs (Venovenous ECMO) and the other for both heart and lungs (Veno-arterial ECMO). In this process, two tubes called cannulas are placed inside the patient’s veins. This placement depends on what kind of support the patient needs.
When a patient has issues with lung function, but their heart is working fine, the Venovenous ECMO method is used. The tubes are placed either in the neck or legs and they help pump oxygen into the blood and remove carbon dioxide. This setup can also allow the patient to move around and require less sedation.
If a patient’s heart is not able to pump enough blood to their organs, the Venoarterial ECMO method is necessary. This involves placing tubes into the patient’s large central artery (aorta) and veins, either through a small incision in the groin or neck or directly in the heart. This method supports both the heart and lungs.
Through the ECMO process, oxygen is added to the patient’s blood and carbon dioxide is removed, simulating artificial lung and heart function. The oxygenated blood is then returned to the patient’s body, providing essential support when the patient’s lungs or heart can’t work efficiently.
The ECMO circuit works as an ‘exchange zone’ for oxygen and carbon dioxide, adding oxygen to the patient’s blood while removing carbon dioxide. This technique is called ‘sweeping’ – increasing or decreasing blood and sweep flow helps manage the amount of oxygen and carbon dioxide going to the patient. One important aspect of ECMO is maintaining a balance between the patient’s blood flow and the sweep gas flow to maintain normal body functions.
When a patient’s lungs become too damaged or inefficient to provide the body with sufficient oxygen, Venovenous ECMO can be initiated. Here, the oxygen-poor blood is taken from the patient, oxygenated by the ECMO system, and then returned to the patient. The returned blood, rich in oxygen, mixes with the patient’s blood allowing the heart to circulate oxygen-rich blood to the whole body. The level of a protein called ‘hemoglobin’ is also crucial as it’s responsible for carrying this oxygen throughout the body.
On the other hand, when the heart has trouble pumping enough blood for the body, Veno-arterial ECMO is used. Here, the locations of tubes are different. The oxygen levels of all limbs need to be closely monitored. This method can also require additional devices to support left heart functions. ECMO also removes carbon dioxide from the patient’s body, replicating the lung’s normal function. When a patient needs oxygen, but also has a lot of carbon dioxide in their blood, ECMO can be used to remove this excess carbon dioxide, a process easier than oxygenation.
With Venovenous ECMO, carbon dioxide is removed from the blood even at low blood flow rates. Finally, both methods help and support the patient’s body when it is unable to maintain sufficient oxygen and carbon dioxide levels.
Why do People Need Extracorporeal Membrane Oxygenation Weaning
If a person is being treated with VV ECMO, a sort of life-support in critical care situations functioning as an artificial lung, they may be ready to start the process of weaning off this support when the illness affecting their lungs has improved. This means the lungs are strong enough to be tested for how well they can provide the body with oxygen and remove carbon dioxide, which is what we normally do when we breathe.
Similarly, people having support from VA ECMO, a method acting as both artificial heart and lungs, might be ready to come off this treatment when their heart and lung disease has improved. This means that both their heart and lungs have recovered enough to be tested for their adequate function. The heart’s job being to pump the blood and the lungs’ job being to enrich that blood with oxygen before it is circulated throughout the body.
When a Person Should Avoid Extracorporeal Membrane Oxygenation Weaning
The patient still shows signs of heart and lung failure, so they’re not yet ready to stop medical support. Depending on the nature of their illness, they might need more time to recover from their heart or lung condition. They may need the help of a device that helps the heart pump blood, known as a ventricular assist device, or they may even need a new heart or lung through a transplant.
Equipment used for Extracorporeal Membrane Oxygenation Weaning
A machine called an ECMO, which includes an oxygenator and an artificial lung (this is a special machine designed to takeover the functions of the heart and lungs, complete with all necessary tubes and monitors)
A special hospital unit called an intensive care unit
A well-equipped lab capable of analyzing blood samples from your arteries
Devices capable of performing both transthoracic echocardiography and transesophageal echocardiography. These are different types of tests that utilize ultrasound technology to create images of your heart in order to check its function.
Who is needed to perform Extracorporeal Membrane Oxygenation Weaning?
In your medical team, there are several key professionals who will work together to deliver your healthcare services. These include specialty doctors, nurses, and other health experts. Each member of this team plays a crucial role in your recovery journey.
The critical care physicians, also known as the Intensive Care Unit (ICU) doctors, play the central role. They have special knowledge and experience in treating serious and complex health issues.
There are different types of surgeons in the team, such as cardiothoracic surgeons (who operate on the heart and lungs), vascular surgeons (specializing in blood vessels), and trauma or acute care surgeons (who handle severe injuries or sudden serious illnesses).
Your treatment may also need the help of ECMO (Extracorporeal Membrane Oxygenation) coordinators and technicians. This is a life support treatment that uses machine to pump and oxygenate your blood bypassing your heart and lungs. The ECMO team ensures the machine is working properly.
You also have ICU nurses looking after you round the clock. They ensure you are comfortable and respond to your needs immediately.
ECHO technicians are the ones who use ultrasound technology to look at your heart and its blood flow. They play a significant role in assessing your heart health.
Respiratory therapists help patients who are having troubles with their breathing. They will guide you with breathing exercises and provide treatments to help your lungs function better.
Lastly, physical and occupational therapists play a crucial role in your recovery. Physical therapists help you regain strength, balance, and mobility through different exercises. Occupational therapists, on the other hand, teach you how to perform daily activities more effectively and independently despite your health condition.
Each team member is here to provide the best care and ensure you make a smooth and successful recovery.
Preparing for Extracorporeal Membrane Oxygenation Weaning
Extracorporeal Membrane Oxygenation, or ECMO, is a treatment that uses a machine to take over the work of the heart and lungs. It’s often used for patients who are very ill, and weaning a patient from an ECMO, whether it’s venovenous (VV) or venoarterial (VA), is a big step in their recovery. However, it’s important to remember that just because a patient is ready to start weaning from the ECMO machine, it does not automatically mean they will fully recover.
Before starting to wean a patient from the ECMO machine, several things need to be in place. Trained medical staff should be ready to go back to full ECMO support if the patient needs it. The patient also has to be stable with a steady heartbeat and blood pressure levels. If the patient still has signs of heart or lung failure, doctors should hold off trying to wean them off ECMO. Some patients might not be the best fit for weaning and in these cases, doctors may consider other options like a transplant or installing an assistive device.
Monitoring a patient’s condition to prepare them for weaning involves checking their physical wellbeing and lab test results, as well as using echo imaging to see the heart function and wellbeing directly. Echocardiography, or echo, is an ultrasound test that allows doctors to see pictures of the heart and the areas surrounding it. This imaging test helps to track the recovery of the heart and identify new problems that might come up. There are several indicators from an echo test that might suggest that a patient could find it hard to be weaned from ECMO. For example, it might suggest issues with the heart’s pumping function, fluid accumulation around the heart, low volume of blood, or high blood pressure in the arteries of the lungs.
Generally, before weaning can occur, patients should have a specific measure of heart’s pump function, called the ejection fraction, that is greater than 25 or 30%. In addition, they should show specific standards of blood flow and heart valve movements while receiving only minimal support from the ECMO machine.
How is Extracorporeal Membrane Oxygenation Weaning performed
Coming off VV (veno-venous) or VA (veno-arterial) ECMO (Extracorporeal Membrane Oxygenation, a treatment that uses a pump to circulate blood through an artificial lung back into the bloodstream) can be quite challenging. This process is unique to each patient, and there isn’t a one-size-fits-all approach.
For VA ECMO, weaning off starts when the initial cause of the heart not pumping blood effectively has been addressed. Key indicators like blood pressure, oxygen levels, and heart function are monitored. The weaning process starts by reducing the pump flow in the ECMO device.
Patients often need medication to support their heart, and may also have devices that assist the heart. During weaning, the heart’s function is monitored closely. Each time the ECMO flow is reduced, the heart’s performance is assessed using ultrasound imaging. It’s also important to maintain optimal settings on the ventilator.
When the ECMO pump flow is gradually reduced, the patient’s heart starts handling more load and its performance can be monitored. If the patient is showing signs of not coping when ECMO support is reduced, full ECMO support will be reinstated. If the patient is managing well with a reduced ECMO support, this indicates that the weaning process is successful.
During this process, if the patient shows signs of distress, the ECMO support is restored. When the weaning process is successfully completed, the ECMO cannulas (the tubes inserted into the patient) can be removed. Once fully weaned from ECMO, the patient needs continuous monitoring to ensure their organs are getting the blood they need.
As for weaning from VV ECMO, the patient’s lung ability needs to have recuperated a significant amount. This involves assessing lung function and reducing ECMO support as lung performance improves. Oxygen provided to the lungs from the ECMO is then slowly reduced, with changes in oxygen and blood gas levels closely monitored.
With both VV and VA ECMO, during the transition period, medical staff closely monitor the patient’s comfort and vitals, making sure the process goes smoothly. The goal is to decrease support from ECMO gradually without causing distress to the patient.
Possible Complications of Extracorporeal Membrane Oxygenation Weaning
Some patients may not be deemed suitable for a process known as “weaning” or they could start well but face issues later on. “Weaning” in medical terms refers to the process of gradually reducing the amount of medical support a patient receives, such as taking them off a ventilator, after their condition improves.
This process, however, sometimes comes with various complications, including:
* “Bleeding”, which implies that blood is flowing out of vessels and into parts of the body where it is not supposed to be.
* “Ischemia to limbs” refers to a situation where the blood flow to the arms and legs is restricted, hindering supply of oxygen and nutrients to these areas.
* “End organ hypoperfusion” suggests that blood is not flowing to the organs as it should. This lack of blood flow can lead to organ damage.
* “Neurological complications” means that there could be problems related to the nervous system, which includes the brain, spinal cord, and nerves.
* “Infections” indicate that harmful microorganisms have invaded the body and are causing disease. This could happen anywhere in the body and could potentially lead to several complications.
What Else Should I Know About Extracorporeal Membrane Oxygenation Weaning?
Understanding when to stop ECMO
ECMO is a life-saving treatment in which a machine does the work of one’s heart and lungs when they can’t do it themselves. Deciding when a person is ready to stop using the machine is based upon certain signs and tests:
* No presence of lactic acid, according to laboratory tests
* Examination by ultrasound (echocardiogram) showing a fully recovered heart, pumping more than 25% of its volume each beat
* Other specific heart measures based on the speed and strength of blood flow, and the depth and speed of heart muscle movement – all staying at healthy levels during the minimum level of ECMO support
* Healthy pulse pressure, the difference between high and low blood pressure readings – the higher this is, the more likely one can stop ECMO
* No signs of the heart chambers becoming enlarged with stable pressures on both sides of the heart
Understanding factors predicting survival once off ECMO
Once the patient stops using ECMO, there are certain factors that could affect their chances of survival:
* An age greater than 60 years old
* Extended use of ECMO that resulted in complications
* A low pH (more acidic) and high levels of lactic acid, indicating that the body isn’t getting enough oxygen
* A high score on a test that measures organ failure
If a patient can’t be weaned from ECMO, it’s important to identify this quickly. There should then be discussions about other long-term support measures. For example, the patient may need a machine to help the heart pump blood (ventricular assist device) either as a short-term solution until they can have a heart or lung transplant or as a permanent solution for the rest of their lives.