First introduced for clinical use in 1972, extracorporeal membrane oxygenation (ECMO) is a form of prolonged cardiopulmonary bypass to treat respiratory and cardiac failure. Since earliest reports of pathologic findings attributable to ECMO published in the 1990s,¹ there have been several technical improvements that have lessened the complication rate. These improvements include the development of more biocompatible materials, more efficient oxygenators, refinements in double lumen cannulas, and smaller, less thrombogenic circuits that decreased turbulence and hemolysis.^2,3

ECMO was initially used in neonates but is now a common therapy in older children and adults. ECMO circuits consist of cannulas, which are typically double-lumen catheters or surgically placed conduits, an oxygenator, and a centrifugal pump. There are two major configurations (Table 61.1). Venoarterial ECMO provides circulatory support as well as oxygenation. Venovenous ECMO has a lower risk of central nervous injury and mortality but requires adequate biventricular cardiac output. Central venoarterial ECMO requires cannulation of the right atrium and returns blood to the ascending aorta via surgical anastomoses. Peripheral venoarterial ECMO utilizes catheters, inserted in the femoral or internal jugular vein and common femoral artery, and is typically used in children. Central venovenous ECMO involves two cannulas in the right atrium, and peripheral venovenous ECMO drains blood from the femoral or jugular vein and returns it through the internal jugular vein.⁴ In autopsies, venovenous or peripheral arteriovenous ECMO is often not readily apparent, especially if the catheters have been removed. Central arteriovenous ECMO is generally used in patients with recent heart surgery and postoperative heart failure and is evident postmortem by synthetic cannulas sutured to the ascending aorta and right atrium, which course outside the chest.

In venovenous ECMO, pulmonary blood flow and pulsatile systemic flow are maintained by native cardiac function, with preserved oxygenation of blood in the left ventricle and aortic root.³ Venous emboli are filtered by the patient’s native lungs. In contrast, venoarterial ECMO, especially peripheral, results in decreased oxygenated blood flow to the left ventricle and aortic root, and there is a greater risk of systemic thromboembolism, ischemic extremities, misdistribution of oxygen, and increased left ventricular wall tension.²

In children, there are a variety of respiratory conditions that may necessitate ECMO treatment. Acute respiratory distress syndrome (ARDS) due to prematurity is currently an uncommon indication, as other treatments have become available. More frequent indications include respiratory failure secondary to meconium aspiration syndrome or persistent pulmonary hypertension of the newborn (Table 61.2).

In adults, there are several indications for ECMO (Table 61.3). ECMO may be used as a bridge to transplant and may allow some patients to be removed from mechanical ventilation and have relative autonomy in preparation for transplantation. Venovenous ECMO is often sufficient, although acute exacerbations can lead to pulmonary hypertension, right-sided heart failure, and the need for venoarterial ECMO.⁵

Acute pneumonia, especially influenza A (H1N1), can be successfully treated with ECMO. The pandemic in 2009 created a resurgence of interest in venovenous ECMO for the treatment of life-threatening lung infections.⁶

The utility of ECMO in the treatment of acute respiratory distress syndrome is unclear, as the mortality remains high even with this therapy. The efficacy and cost of ECMO treatment for ARDS, in comparison to mechanical ventilation, have been reviewed.^7,8 Venovenous ECMO is the preferred method, even if there is transient acute right heart failure secondary to ARDS, since oxygenation of pulmonary artery blood will decrease hypoxia-induced vasoconstriction.²

Patients with complicated open heart surgery develop heart failure and are unable to be weaned from bypass at a rate of about 1%. Arteriovenous ECMO, often with aortic balloon pump placement, is an accepted treatment for these patients.⁹

ECMO has been used for cardiopulmonary support for organ donation after neurologic determination of death.¹⁰