FREQUENTLY ASKED QUESTIONS ABOUT ECMO:
1. WHAT IS ECMO?
ECMO stands for Extracorporeal Membrane Oxygenation. It is a method of providing oxygen for the body when someone’s lungs and/or heart are not able to supply oxygen on their own. With ECMO, blood leaves through a catheter that sits in a large vein and connects to an oxygenator machine. The blood then returns to the body through an artery or vein using a different catheter.
Check out our friend Shannon’s awesome animated film explaining ECMO in more detail:
You can see more of Shannon Impellicceiri’s work on her website here.
2. WHAT IS THE DIFFERENCE BETWEEN V-V AND V-A ECMO?
The difference between V-V and V-A ECMO is how the blood returns to the body. In all forms of ECMO, blood leaves through a large vein to the ECMO machine. In V-V ECMO, the blood returns through a large vein. In V-A ECMO, the blood returns through a large artery. Veins are the vessels that bring blood to the heart and the heart then pumps blood through arteries. When a patient’s lungs fail, the main role of ECMO is to provide large amounts to oxygen to the body. This can be done by supplying blood to veins as long as the heart can still pump blood to arteries. If there is a choice, we prefer to use V-V ECMO over V-A ECMO since V-A ECMO has more side effects (see #4 below). When a patient’s heart fails, it cannot effectively deliver blood to the body. For this reason, the returning blood from ECMO must “bypass” the heart and pump directly through a large artery. When a patient’s lungs and heart fail, we use V-A ECMO also.
3. WHY DOES SOMEONE GET PLACED ON ECMO?
Doctors place patients on ECMO when patients are not able to supply oxygen to the body. Patients’ lungs fail for a number of reasons including pneumonia, lung cancer, pulmonary edema, pulmonary embolism, and COPD. When a patient’s lungs fail, he/she first is intubated (breathing tube) and hooked up to a ventilator (breathing machine). However, sometimes lungs are so damaged that providing oxygen through intubation is not enough. This is when doctors turn to V-V ECMO. A heart can fail for many reasons including heart attack, pulmonary embolism, bad valve disease, or worsening heart failure. When a heart fails, doctors try to fix the underlying problem. They may also start medications (called ionotropes) to help improve the pump function of the heart. If medications are not enough, doctors will turn to V-A ECMO.
4. WHAT ARE THE SIDE EFFECTS OF ECMO?
ECMO has a number of side effects. Whenever large catheters are placed in patient’s veins and arteries there is risk of bleeding and infection. Large catheters also have a risk of causing clots. For this reason, all patients on ECMO are placed on blood thinning medication called heparin. This further increases the risk of bleeding. V-A ECMO has the additional risk of causing low blood flow to certain parts of the body. For example, if the return catheter through an artery is in the left thigh, there might be very low oxygen levels in the right hand. Also if the catheter in the left thigh points toward the head, there is a risk of low blood flow to the left foot. To help prevent this, we monitor oxygen levels at multiple places on the body.
5. HOW LONG CAN SOMEONE STAY ON ECMO?
That is a complicated question. Due to the risks of ECMO discussed above, doctors try to keep patients on ECMO for as short a time as possible. Often patient will be on ECMO for several days up to 1-2 weeks. Every day, several blood and imaging tests are done to determine if a patient is ready to come off ECMO. As the technology of ECMO improves, hopefully side effects will decrease and patients can remain on ECMO for longer periods of time.
6. WHAT IS THE DIFFERENCE BETWEEN ECMO AND A VENTILATOR (BREATHING MACHINE)?
Both ECMO and a ventilator aim to provide oxygen to the body when the patient’s own lungs and breathing are failing. The ventilator assists the patient’s own lungs by pushing oxygen with pressure into the lungs. ECMO instead provides oxygen directly via a catheter placed in a patient’s vein or artery. We almost always try oxygenating a patient with a ventilator first. However, when a patient’s lungs are too sick for this, we turn to ECMO to assist in providing oxygen to the body. V-V ECMO provides oxygen through a vein. This blood then has to travel to the heart and be pumped around the rest of the body through arteries. Therefore, with V-V ECMO or with a ventilator, a patient must have a well-functioning heart to get the oxygen pumped throughout the body. V-A ECMO has the additional advantage of pumping blood directly to arteries. This “by-passes” the heart and is therefore the method of ECMO we use when a patient’s heart is failing. It is not used routinely because there are greater side effects with V-A ECMO (See question 4).
7. WHAT DAILY TESTS NEED TO BE DONE FOR SOMEONE ON ECMO?
Patients on ECMO are constantly monitored. They require continuous monitoring of their vital signs, including their blood pressure and oxygen levels. In addition, they require blood tests each day. They must be tested for anemia, since normal blood counts are essential for ECMO to work best. The team will also look for signs that certain organs are receiving enough oxygen. Kidney function should be checked every day. Each day a patient should have a neurologic exam to ensure he/she is receiving enough oxygen delivery to the brain. Arms and legs must be examined also to make sure oxygen is traveling to all four limbs and that there have been no complications from a catheter insertion.