'Father of ECMO': When a Ventilator Isn't Enough

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An early hallmark of pneumonia caused by SARS-CoV-2 is severe refractory respiratory failure. Many COVID-19 patients require treatment with mechanical ventilation fairly early in their disease course, and some patients fail to respond even to maximal ventilatory support. In such cases, clinicians at some hospitals began using a resource-intensive technology known as extracorporeal membrane oxygenation (ECMO) as a treatment of last resort for select patients with COVID-19.

Because the pandemic is still raging across the country, it will be some time before we fully understand the benefits and outcomes of ECMO for COVID-19 patients. Medscape spoke with the "father of ECMO," Robert Bartlett, MD, about the use of this life-sustaining technology for patients with COVID-19.

What is ECMO, in a nutshell?

ECMO is a modified heart-lung machine that takes over the function of the lungs for days, weeks, or even months, until those organs have recovered or a transplant is performed. The patient's blood is diverted from the body to the ECMO device, where it is oxygenated and cleared of CO₂, before being returned to the body. Unlike a cardiopulmonary bypass machine used in heart surgery to temporarily take over the function of the heart and lungs, ECMO can be used as long as required to allow the lungs to rest and recover from the harmful effects of the virus.

You are called the "father of ECMO." What was your role in developing the technology?

I get the credit for developing ECMO, although there were other labs and investigators working on it. This was back in the 1960s. The heart-lung machine for heart surgery had been developed in the 1950s, but it could only be used for an hour or so. Our research, then, was figuring out how the heart-lung machine could be used safely for a much longer period of time. The solution was to create a membrane type of oxygenator, which takes over the lung's function of gas exchange.

A handful of hospitals around the country got into the development after our lab research. The first clinical cases took place in the 1970s. We tried ECMO on a variety of patients; however, at that time, it was not very successful with adults in heart or lung failure. But it worked well for children — mostly newborn infants with respiratory failure. So the first few years of development was mostly in newborns.

(Note: the acronym "ECMO" isn't quite accurate, because the technology can remove CO₂ as well as oxygenate the blood. For this reason, many people currently refer to this technology as "extracorporeal life support.")

How is ECMO used in COVID-19? Are there any concrete indications or contraindications?

The indication for ECMO is simple: a patient with respiratory failure who is not responding to mechanical ventilation. ECMO is used after all of the conventional means of support have been tried (proning, mechanical ventilation, oxygen). The mortality rate among these ICU patients is very high.

There's been discussion about the potential of initiating ECMO earlier in the disease course — perhaps even before trying mechanical ventilation — but no one is seriously doing that. The risks are significant, particularly bleeding problems.

ECMO, like conventional mechanical ventilation, doesn't treat COVID-19, but it keeps the patient alive while the disease runs its course. The primary goal is to keep patients on ECMO long enough so that their lungs can recover. Therefore, when we start ECMO, we turn the ventilator off so the lungs are no longer exposed to the barotrauma from positive-pressure ventilation.

There is no "ideal patient," but younger, previously healthy patients are most likely to benefit from ECMO. How old is too old? It's a question of physiology rather than age per se, but with COVID-19, most centers are using a cutoff age of 60 years.

The basic ECMO indications and contraindications for COVID-19 are the same as for any diagnosis. We wouldn't use ECMO on a patient with a very poor prognosis (severe head injury or stroke, for example).

What type of vascular access is used for patients with COVID-19?

The two primary ECMO circuit configurations are veno-venous (V-V) and veno-arterial (V-A). For patients with pure respiratory failure, we use V-V ECMO (the most common), which supports the lungs but not the heart at all. If the patient also has heart failure, then we would use a V-A configuration, which supports both the heart and lungs.

How long do patients with COVID-19 typically remain on ECMO?

With any viral pneumonia, it takes 10 to 14 days for the lungs to recover. It's not unusual, though, for patients to be on ECMO for 2 to 3 months before they recover. The downside of that scenario is that the ECMO machine is tied up for many weeks and is not available for other patients.

What risks, if any, are associated with ECMO?

During ECMO, the blood must be anticagulated, so the major risk is bleeding. It occurs in about 30% of patients. We manage it by measuring the extent of anticoagulation, titrating the dose, improving other aspects of coagulation (such as platelets), and sometimes turning off the anticoagulant altogether, realizing the circuit will clot and must be replaced.

Do we have any outcome data yet for COVID-19 patients treated with ECMO?

The survival rate right now is 50% to 60%. Many of the patients in the registry are still on ECMO, so the final outcome is not known. Some centers are reporting 80% survival with ECMO. The Extracorporeal Life Support Organization (ELSO) maintains a registry of COVID-19 cases on ECMO throughout the world. As of July 21, a total of 1909 suspected or confirmed COVID-19 patients have been treated with ECMO. Of 1305 known outcomes, 722 (55%) were discharged alive.

During a pandemic, it would seem that many more patients could benefit from ECMO than can be accommodated. How widely available is ECMO?

Currently, about 800 centers around the world are providing ECMO (ELSO maintains a map of ECMO availability). If a patient who needs ECMO is admitted to a hospital without an ECMO program, the patient can be transported to an ECMO center. The key is to send the patient as early as it is recognized that they aren't doing well on conventional lifesaving therapies.

The limiting factor isn't the number of machines or beds but having staff who are fully trained in ECMO. An ICU nurse with some extra training can manage both the patient and the ECMO machine.

Most hospitals can handle two to four patients at the same time, depending on the size of the team. At the University of Michigan, we can treat 12 ECMO patients at the same time, and there is a hospital in Paris with the capacity for 20 patients on ECMO.

Early in the pandemic, the FDA gave emergency approval to all available ECMO devices, which has been valuable in increasing access to ECMO. We've seen growth in the number of hospitals able to provide ECMO to COVID-19 patients.

Are there any long-term sequelae in adults who have been on ECMO?

Long-term sequelae from ECMO in children or adults are related to the primary disease and not to ECMO. Patients who have been in shock or had profound infections such as COVID-19, as we are learning now, have a variety of symptoms months after the acute phase of their disease. SARS-CoV-2 is a virulent virus, and some patients will have pulmonary symptoms, weakness, and other sequelae for weeks or months after they have recovered.

Robert H. Bartlett, MD, is professor emeritus, Section of General Surgery, Division of Acute Care Surgery, at the University of Michigan. He is widely known for his groundbreaking research in ECMO, which has saved thousands of lives during the past 4 decades.

Laura Stokowski still clearly remembers the day she first met Dr Bartlett, when ECMO was introduced to the newborn intensive care unit in the early 1980s. She was the nurse who took care of the first neonate to receive ECMO therapy at the University of Michigan Mott Children's Hospital.

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Cite this: 'Father of ECMO': When a Ventilator Isn't Enough - Medscape - Jul 22, 2020.