ECMO (otherwise known as extracorporeal membraneous oxygenation) is essentially a life support measure used when the lungs or both heart and lungs cannot function adequately with traditional mechanical ventilation support. In ECMO, blood is drained from the body, diverted to an oxygenator where gas exchange takes place, then returned to the patient. There! Now you know everything you need to know about ECMO. Just kidding! Let’s start at the very beginning.
Normal gas exchange, super simplified
Gas exchange depends on two processes…ventilation and perfusion. Ventilation (the process of breathing in and out) brings air into the alveoli and gets carbon dioxide out of the body. Perfusion refers to the gases utilizing pressure gradients to diffuse across membranes…basically, oxygen goes in while carbon dioxide goes out. So, as you take a breath in, oxygen floods the alveoli and permeates into the capillaries and attaches to the red blood cells. This oxygen-rich blood then travels out of the lungs, to the left side of the heart and then is pumped out to the rest of the body. When this oxygen-rich blood gets to the capillary beds in the body’s tissues (which are very permeable as well), oxygen goes into the tissues in exchange for carbon dioxide. The blood, now more-or-less depleted of oxygen and loaded up with CO2 travels back to the lungs where it will diffuse into the alveoli and be exhaled.
Why use ECMO?
ECMO is heavy heavy life support. Think about a patient undergoing a coronary bypass procedure…the heart is stopped and blood is diverted to the cardiopulmonary bypass machine while the surgeon does her thing and fixes the heart. At this moment, the patient’s entire cardiopulmonary function is being supported by a machine…it’s the heaviest form of life support there is, and thankfully it’s only used short-term during surgical procedures. ECMO is essentially a partial form of cardiopulmonary bypass…gas exchange takes place outside the body as a way to bypass the lungs and then pumped back into the body, giving the lungs and heart a chance to “rest.” It is used when all other forms of ventilatory support have failed (or are about to fail). Like I said, it is heavy heavy life support. But also very very cool.
So who gets ECMO? Basically your patient with severe ventilation/perfusion problems that can’t be overcome with standard mechanical ventilation or whose heart function is impaired. Typical situations include ARDS without organ failure, patients recovering from heart failure, respiratory failure or heart surgery and patients needing a “bridge” treatment while the medical team ponders treatment options or while the patient is awaiting a LVAD or lung transplant. Pretty cool, huh?
Two types of ECMO
The two most common types of ECMO are VV-ECMO (veno-venous) and VA-ECMO (veno-arterial). In VV-ECMO the blood is returned to the body via venous circulation, while in VA-ECMO it is returned to the body via the arterial system. VV-ECMO is essentially used for pure respiratory support, whereas VA-ECMO provides some support to the cardiovascular system as well.
In VV-ECMO, blood is pulled from a large vein (such as the femoral), run through the oxygenator where gas exchange takes place, and returned via a large vein. In VA-ECMO (most commonly used in resuscitation efforts and when the heart AND lungs are compromised), blood is drained via a large vein (the femoral is a typical one) and returned via an artery. Click here for a great diagram and summary of these two types of ECMO.
Getting a patient on ECMO
The process of getting a patient on ECMO involves a surgical procedure to cannulate the veins/artery used…typically this is done at the bedside and may involve the use of fluoroscopy to ensure proper placement. Your patient will be sedated and given pain medicine as well as a pretty good dose of heparin to prevent the blood from clotting off the oxygenator or the tubing. Curious as to what this entails? Here’s a video for you (not for the squeamish…but hey, you’re nurses…you can handle anything!).
Nursing care of the ECMO patient
Monitor respiratory function: This is a no-brainer…your patient wouldn’t be on ECMO if he was oxygenating like a champ, now would he? You’ll be doing serial ABGs and VBGs, plus keeping an eye on EtCO2 and SpO2. Expect daily chest x-rays and work with your respiratory therapist to keep those lungs as clear as possible.
Monitor hemodynamics: This is a biggie when you are running VA ECMO (VV ECMO doesn’t affect hemodynamics as it is only for respiratory support). You’ll be watching cardiac function (keep an eye on that HR, MAP and CVP!), tissue perfusion and temp. Why the temp? Recall your oxyhemoglobin disassociation curve, right? (If not, don’t worry…you’ll be introduced to it soon enough!). The lower your temp, the lower the oxygen consumption is…so you’re going to keep fevers DOWN in this patient!
Monitor neurological status: With ECMO, there is a significant risk for ischemic or hemorrhagic stroke, so you’re going to be watching neuro status like a hawk. If your patient is sedated (and most of them are) you’re going to be keeping an eye on those pupils, getting ultrasounds regularly to assess for clot formation, and watching for response to painful stimuli.
Monitor renal function: As with any and all critically ill patients, you are going to be very concerned about renal function. You will be calculating I/Os hourly, watching for fluid overload, giving diuretics as needed and monitoring labs (BUN, creatinine and all electrolytes). Patients who are in renal failure will require CRRT (continuous renal replacement therapy…a whole other can of worms!).
Skin Skin Skin: Good nurses are super vigilant about their patients’ skin. Turn q 2, float heels, keep linens wrinkle-free, pad areas where tubing touches skin, and maintain cleanliness at all times.
What could possibly go wrong?
ECMO is serious business, and the risk for complications is great. The main ones are: ischemia, bleeding, infection, air embolism and inadvertent decannulation. So, what are you going to do about it?
Ischemia is due to low perfusion or thrombosis, so you’re going to be
monitoring cap refill, distal pulses, and skin signs (color, temp) very carefully. You may need to pull out the Doppler if your distal pulses are difficult to palpate. If ischemia is going to develop in the limbs, you’ll see it in the toes most likely before the fingers…but keep a close eye on both if they start to feel cool, turn dusky or you lose pulses! (check out this post for a moment-by-moment scenario of a patient with limb ischemia due to compartment syndrome…different cause but many of the monitoring parameters for ischemia are the same.)
Bleeding is another huge risk in the ECMO patient due to the heparin used to prevent the system from clotting off, so you’re going to follow basic bleeding precautions: no injections, no new lines, soft toothettes only, nothing PR unless OK’d by MD. For labs, you’ll be following your coags and CBC regularly…PT, PTT, Protime, INR, Platelets, H&H…you get the idea. Be VERY careful when suctioning your patient…if you see blood at any time while suctioning…STOP! Also, keep an eye on that Foley catheter, too!
It goes without saying that infection is a gigantic risk for your ECMO patient. Keep a close eye on WBC, temp and urine characteristics…alert the MD if the urine turns cloudy or develops sediment (both signs of possible UTI).
Probably one of the scariest complications to even think about is air embolism (when air enters the circuit and gets into the patient). Keep in mind that air embolism can occur from ANYWHERE, not just the ECMO circuit. How many gtts do you have running? How many invasive lines are you using for hemodynamic monitoring? Check that all connections are secure ROUTINELY and take all “air in line” alarms seriously. What do you do if you suspect air embolism? Trendelenberg, left side, call cardiologist STAT! If your patient is compromised, then begin CPR!
And, of course, it wouldn’t be all fun and games without mentioning the risk of accidental decannulation…whether your line comes out partially or all the way, this is a big emergency! With a partial decannulation, hemondynamics may be partially maintained (depends on how “partial” we’re talking about), but with a full decannulation, hemodynamics will fail and you need to hop on the chest immediately with some high-quality CPR.
So, are you totally terrified of ECMO yet or super jazzed? Probably a mixture of both…as you should be. Please take note that ECMO is much, much more complicated than this simple overview…it involves highly trained specialists, amazing technology, a courageous patient and family, and a dedicated and extremely attentive nurse. I hope this introduction to ECMO piques your interest in critical care…we need more of you!
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