The Edge: Moving ECMO Patients, Part 1

The Edge is a monthly blog series developed by EMS World and FlightBridgeED that features top EMS leaders exploring the intricacies of critical care in EMS practice. In this installment Jeremiah Gleitz, BAS, FP-C, CCP-C, begins a 2-part look at extracorporeal membrane oxygenation, or ECMO.

It’s January, 24ºF outside, and you show up for your 1900 shift. You and your partner catch up on the latest updates from the day crew, check over your aircraft, and brief with your pilot. Shortly after briefing the tones drop. It’s an ECMO transport from one of your regular referral hospitals in a neighboring state, returning to an ECMO center near your base. Due to distance and the complexity of the patient, fixed-wing transport is being utilized. Your pilot checks the weather and duty time and advises this flight will be a go. 

Communications advises you this will be for a 54-year-old male, failed cardiac bypass, on venoarterial ECMO. He is intubated, sedated, and currently on 9 different drips. A perfusionist will accompany you on the flight and be at the airport in 35 minutes. 

As you converse with your partner, you identify the following transport considerations: 

• Do you have adequate oxygen for the trip? Your pilot advises the return flight time will be 1 hour and 45 minutes. 
• Do you have enough IV pumps (or channels) to accommodate 9 different medications?
• Do you have adequate medications to complete the mission (or can you obtain enough from the sending facility)?
• Do you have chargers for all your equipment? 
• Are hangars available at both the referring and receiving airports to help with thermoregulation of the patient and ECMO circuit?
• Are you adequately prepared to manage and treat this patient for the roughly 5 hours of care time you will have? 

After preparing additional equipment and supplies, you call to get a report from the bedside nurse at the sending facility. Shortly thereafter the perfusionist arrives with her equipment, and you brief before departing. 

Overview

ECMO is an acronym for extracorporeal membrane oxygenation. Patients on ECMO have large plastic cannulas inserted into vessels in their neck, groin, or centrally through their chest. These cannulas are attached to a large tubing circuit that runs to what functions essentially as an artificial lung. This artificial lung, or oxygenator, performs two roles: It removes carbon dioxide from the blood while simultaneously introducing new oxygen into the blood before the blood is returned to the patient via cannulas. Often a warming unit is attached to the oxygenator to assist in thermoregulation of blood returned to the body. This is all done through a centrifugal pump. Think of it as similar to a cardiac bypass machine used in operating rooms but on a smaller and more compact scale. 

ECMO isn’t a magical cure for everyone. There have been some incredible success stories in recent years about individuals placed on ECMO as a last resort, but placing anyone on ECMO is a temporizing measure. ECMO is often referred to as bridge therapy, meaning it’s a means to a goal. It provides mechanical support that allows workload to be removed from the heart and lungs, which gives these organs time to rest and heal. ECMO may be a bridge to transplant, another long-term support device such as a ventricular assist device, or to allow a cardiovascular surgery team to repair vasculature. In the end ECMO has many uses, a lot of which are still being explored today. However, they all require an end game that will allow for decannulation in the not-so-distant future.

Venoarterial and Venovenous

Diving a little deeper, let’s discuss the two most common types of ECMO. There are more, but for our purposes we’ll focus on venoarterial (VA) and venovenous (VV). 

Venoarterial simply means you have one cannula inserted into a vein and one in an artery. Blood is pulled from the venous system and sent through the oxygenator, where carbon dioxide is removed and oxygen is added, and then returned into the arterial system. Where the cannulation site is located determines where this oxygenated blood is returned to the bloodstream. Common cannulation sites are peripherally in the femoral vein or internal jugular vein and femoral artery. 

Of note, when peripheral cannulation occurs in VA ECMO, flow is retrograde, meaning it is pulled from the venous system and replaced into the arterial system but flowing against the native blood flow. This only occurs in peripherally cannulated VA cases. Another cannulation configuration you may see is central cannulation, which involves a sternotomy followed by placement of the venous cannula directly into the right atrium and the arterial cannula directly into the aorta. Where you practice, the patient’s disease pathology, and what their support needs are will determine what type of cannulation is performed. VA ECMO provides pulmonary support as well as cardiac support. 

Venovenous ECMO provides primarily pulmonary support, meaning if there is a need for cardiac support, it likely isn’t the best option. The uses for VV ECMO are numerous, but a few common examples are acute respiratory distress syndrome (ARDS), inhalation injuries that affect the lungs, profound hypoxemia in the presence of aggressive ventilator settings, and, more recently, COVID-19. VV ECMO cannulation sites are typically peripheral and don’t bypass the heart. You may see 2 cannulas or 1 bicaval dual-lumen cannula, depending on which option is chosen. Regardless of the option, deoxygenated blood is removed from the venous system via the right internal jugular or a femoral vein and flowed through the oxygenator, where CO₂ is removed and oxygen added, before it is returned into the venous system. 

At an elementary level there are several different controls or inputs that impact how ECMO will affect your patient. 

Flow—This is controlled by adjusting revolutions per minute on the centrifugal pump, thereby changing the amount of flow in liters per minute. Whether VA or VV ECMO is being used dictates what your flow will be. Typically liter flows range between 2–5 lpm, depending on which modality is being used and the size of 
the cannulas. 

Oxygenation—This is done through a blender that can provide 21%–100% FiO₂. Your patient’s SvO₂ and arterial blood gasses will guide this titration. 

Sweep—This is essentially how much carbon dioxide is being removed. Think of it at a very basic level as minute volume. With a larger minute volume, you’re going to blow off more CO₂. The same thing occurs here: The higher the sweep, the more CO₂ is removed from the blood as it crosses the oxygenator. The lower the sweep, the less CO₂ is removed. 

Look for the second part of this article in next month's issue. 

Jeremiah Gleitz, BAS, FP-C, CCP-C, is a critical care flight paramedic and regional clinical manager with Life Link III in Minneapolis, Minnesota. He is also an ECMO specialist with the Life Link III mobile ECMO team in collaboration with the Center for Resuscitative Medicine at the University of Minnesota.