Extracorporeal membrane oxygenation, or ECMO, was initially developed as an extension of cardiopulmonary bypass to replace the function of the heart and lungs by pumping and oxygenating a patient’s blood outside the body. The procedure, once only able to be used for hours or days at a time, can now support patients for months uninterrupted, offering a bridge to recovery or further treatment that will save a patient’s life. Anesthesiologists are increasingly at the forefront of this evolving method of mechanical circulatory support, offering unique expertise that combines knowledge and skill.
A brief overview
“ECMO is a bridging therapy to recovery or a destination therapy such as an artificial heart or heart transplantation for patients in heart failure, or lung transplantation in patients with respiratory failure,” explained Stephanie Cha, MD, Assistant Professor in the Department of Anesthesiology and Critical Care Medicine, Division of Critical Care Medicine and Cardiothoracic Anesthesia, Cardiothoracic Anesthesiologist, and Critically Care Trained Anesthesiologist and Intensivist at Johns Hopkins University School of Medicine. It is used to assist certain procedures that will only require ECMO temporarily, such as cardiac surgeries, difficult cardiac stents, catheter procedures, and percutaneous procedures performed in the cardiac catheterization lab. However, Dr. Cha continued, the group of patients eligible for ECMO is growing as we develop minimally invasive ways to treat cardiac problems. Higher-risk patients are more often eligible, and there is a greater need for the use of ECMO as a temporary support for larger procedures.
Ronald G. Pearl, MD, PhD, FASA, who is the Dr. Richard K. and Erika N. Richards Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University School of Medicine, noted that there are two major types of ECMO: veno-venous (VV) and veno-arterial (VA), which both roll into the larger category of mechanical circulatory support. VA ECMO, typically used for patients whose heart is not strong enough on its own, is essentially identical to the functions of the cardiopulmonary bypass machine. The technology is different; ECMO can continue for days, weeks, or even months without necessarily harming the patient, and it doesn’t require the high level of anticoagulation to keep blood from clotting in the circuit that a typical bypass machine requires. VV ECMO, alternatively, is used when the lungs are not oxygenating adequately, he said.
“The group of patients eligible for ECMO is growing as we develop minimally invasive ways to treat cardiac problems. Higher-risk patients are more often eligible, and there is a greater need for the use of ECMO as a temporary support for larger procedures.”
The anesthesiologist’s role
Since its inception, the use of ECMO has continued to evolve as technology advances. Dr. Pearl highlighted increasing combinations and options that allow physicians to safely adjust to the patient’s needs and fulfil their physiologic requirements while avoiding any undue harm. This represents a change from even five years ago, and the outcomes are improving as a result.
One consistency throughout the evolution of ECMO has been the anesthesiologist’s contributions. Dr. Cha recalled early success with ECMO in pediatric patients and more common use of the therapy outside of the OR in the 2000s. Anesthesiologists, as experts in physiology, can support patients through the subsequent procedures often needed after being placed on ECMO, such as infection source control, bleeding or clotting complications, and tracheostomy.
“Anesthesiologists were intimately involved in taking care of patients on cardiopulmonary bypass during cardiac surgery in the OR, so they had both the knowledge of patient physiology and of the cardiopulmonary bypass system. When that moved into ECMO, anesthesiologists were in an ideal position to help care for those patients, sometimes as cardiac anesthesiologists and sometimes as ICU providers,” Dr. Pearl said. “There has been an evolution in terms of who takes care of patients after cardiac surgery, and as the practice of ECMO emerged and markedly expanded, the role of the anesthesiologist who provides critical care grew in parallel.”
Though the exact role varies by institution, Dr. Pearl said that anesthesiologists can be the primary provider responsible for care of patients on ECMO by determining whether a patient should go on ECMO; placing cannulas; and starting, managing, and choosing to discontinue treatment. In other institutions, these decisions may involve a cardiac surgeon or critical care physician.
“Dual-trained cardiac and ICU anesthesiologists are often involved in the care of ICU patients undergoing ECMO,” Dr. Cha said. “We have become especially involved during COVID, as so many very acutely ill patients failed conventional therapies such as mechanical ventilation and rescue therapies, especially in the pre-vaccine era. Anesthesiologists were often making decisions as part of a team to determine which patients would be appropriate for and benefit from ECMO.” At the height of the COVID-19 pandemic, Dr. Cha and her colleagues even worked to develop a procedure to safely put patients who were prone or too unstable to tolerate transfer to the OR or catheter lab on ECMO at the bedside. They helped create a remote monitoring program that allowed vital sounds, ventilator wave forms, and other patient data to be viewed without having to use precious time to don PPE before entering the room.
In the OR, anesthesiologists are responsible for maintaining patient stability and can perform the ECMO initiation procedure. Dr. Pearl said the procedure involves placing at least two, and sometimes more, very large catheters with the use of transesophageal echocardiography – something anesthesiologists generally perform during ECMO cannulation. During this procedure, anesthesiologists provide expertise about the function of the heart and may determine any reason to not place a patient on ECMO, make decisions about which type of ECMO to use, and guide catheters into the right position during the procedure to prevent injury to the heart or other structures. Dr. Cha added that cardiac anesthesiologists also have the ultrasound skills and experience to work with seriously ill patients.
A collaborative evolution
As ECMO technology has evolved and its management expanded, it has become a subspecialty of intensive care that offers anesthesiologists an opportunity to interact with patients extensively over a long period of time. Dr. Pearl said that managing patients on ECMO allows anesthesiologists to practice at the highest complexity. With this expanded role comes a new and challenging avenue of practice. Dr. Cha urges anesthesiologists to remember one thing: for every great ECMO success story, there are heart-breaking cases as well. “ECMO is no easy ride for patients or their families, and it always poses a risk for complications,” she said. “It does not replace preventative care in certain populations, such as COVID patients who should be vaccinated and practice good infection control.”