Extracorporeal membrane oxygenation (ECMO) has continued to evolve since the pioneers of cardiac surgery, Gibbon and Lillehei, developed cardiopulmonary bypass in the 1950s. The term ECMO applies to the use of an extracorporeal circuit, consisting of tubing, oxygenator and blood pump, in the setting of cardiopulmonary failure. The original ECMO was veno-arterial (VA) as popularized by Bartlett in the early 1980s. Over the last three decades ECMO has evolved into several forms including VA, veno-venous (VV), arterio-venous (AV), right atrium to aorta (RA–Ao), and pulmonary artery to left atrium (PA–LA). ECMO in some form may be indicated for acute cardiac failure, respiratory failure, or a mixed presentation; the specific application of the therapy will depend on the presentation of the patient. Likewise, several programs have developed ambulatory capability of most forms of ECMO to aid recovery or suitability for transplant. Ambulatory ECMO is often referred to as the “artificial lung.”

Historically, ECMO in the adult was considered “salvage” therapy for patients “dying” from severe respiratory failure despite maximal medical therapy. Some of the oft-quoted trials in the 1980s compared ECMO with conventional medical therapy and failed to show survival advantage. However, there have been significant advances in ECMO, and evidence now favors earlier utilization of the technology to minimize end-organ damage that might occur during prolonged maximal ventilatory and medical support. This is particularly apparent in the case of respiratory failure associated with H1N1 influenza. Survival is approximately 72% for patients placed on ECMO within 6 days of intubation compared with only 30% for patients on ECMO 7 or more days after intubation.¹

ECMO is indicated for the short-to-medium-term management of respiratory failure, cardiac failure, or both. Specifically, patients are evaluated when the native disease process is thought to have an estimated mortality of 50% or greater, is reversible, and/or requires a bridge to transplant. The Extracorporeal Life Support Organization (ELSO) publishes guidelines which cover application of ECMO in the adult. In the case of acute respiratory distress syndrome (ARDS), this would include a PaO₂/FiO₂ ratio of less than 100 despite optimization of ventilator settings.

Special scenarios include H1N1 infection, where early deployment of ECMO is associated with better outcomes, and delay may adversely affect the risk/benefit ratio. In addition, use of ECMO as a bridge-to-transplant for lung recipients should be considered when maximal medical therapy is insufficient. Many programs utilize ambulatory ECMO to improve the respiratory status and conditioning prior to transplant.

ECMO as a bridge to lung transplantation has significantly increased during the last 10 years. A recent analysis of the UNOS database showed that the use of ECMO at the time of lung transplantation has grown 150% in the last 24 months compared to all previous decades (1970–2010). This increase in utilization is reflected in the growing success reported with the use of different ECMO modalities in patients awaiting lung transplantation. We recently submitted our experience with the use of ambulatory ECMO as a bridge to lung transplantation, reporting the use of ECMO in 31 patients with end-stage lung disease. In our series, all of the patients were awake and the vast majority followed an “algorithm-directed” ECMO management program that involved the use of physical therapy and ambulation in preparation for lung transplant. In our series, the 30-day, 1-year, 3-year and 5-year survival was 97%, 92%, 83%, and 66%, respectively.² A summary of a modern series of patients bridged to lung transplant while on ECMO is presented in Table 113-1.

ECMO use is now being considered in awake, nonintubated patients to improve oxygenation, to facilitate ambulation, and to improve physical conditioning prior to transplant.

Indications for ECMO

1. 
   

   Patients with irreversible end-stage lung disease presenting with clinical deterioration (refractory hypoxia or hypercapnia) or lack of response despite the use of invasive or noninvasive mechanical ventilation.

   
   
2. 
   

   Patients with severe pulmonary hypertension refractory to pulmonary vasodilators and/or hemodynamic deterioration caused by right ventricular failure.

   
   
3. 
   

   Patients with severe exercise-induced pulmonary hypertension associated with advanced lung disease, presenting with clinical deterioration and progressive physical decline, and unable to maintain ambulation and good functional status.

Contraindications to the Use of ECMO

1. 
   

   Active bloodstream infection

   
   
2. 
   

   Acute renal failure not responsive to medical therapy (need for dialysis)

   
   
3. 
   

   Hereditary or acquired coagulation disorders (i.e., blood dyscrasia, heparin-induced thrombocytopenia)

   
   
4. 
   

   Evidence of end-organ failure other than the lung

   
   
5. 
   

   Underlying irreversible neurological or neuromuscular disease

Several studies have shown that the use of mechanical ventilation in patients with idiopathic pulmonary fibrosis is not effective and is associated with high mortality rates. Delaying initiation of ECMO in an attempt to maximize alternative medical treatments may result in worsening physical condition, secondary organ dysfunction, and jeopardize their candidacy for possible lung transplantation.

Areas of Controversy

Advanced age (>65 years) is considered by some a relative contraindication for lung transplantation. Nevertheless, several reports have demonstrated good outcomes in patients >65 years of age. A recent report of the use of ambulatory VV ECMO in patients with cystic fibrosis and hypercapneic respiratory failure suggests that patients with severe bronchiectasis or cystic fibrosis can be successfully bridged to lung transplantation without an increased risk for infectious complications.

There are four categories for ECMO cannulation in the adult:

1. 
   

   VV ECMO is indicated for management of isolated respiratory failure. The success of this strategy relies on the patient’s own hemodynamics and only assists with gas exchange. Blood is withdrawn from the right atrium/inferior vena cava (IVC) via a long peripheral cannula inserted via a central vein. Oxygenated blood is returned via a superior vena cava (SVC) cannula into the right atrium with flow directed at the tricuspid valve. The oxygenated blood is then pumped out the pulmonary artery, through the dysfunctional lungs, and then returned to the left heart where it is pumped to the systemic circulation. The Avalon Elite^TM dual lumen cannula (DLC) (Maquet Cardiovascular, San Jose, CA), designed by Wang and Zwischenberger, is a significant advance in the arena of VV ECMO.³ Single percutaneous access of the right internal jugular vein yields several advantages: single-site cannulation, reduced risk for complications associated with femoral or central cannulation, and the ability to allow ambulation by avoiding the use of the femoral site. Placement of the Avalon cannula may be performed bedside in the intensive care unit (ICU); however, it requires either fluoroscopic or echocardiographic guidance for optimal placement of the return and infusion ports.⁴

   
   
2. 
   

   VA ECMO is indicated in the setting of acute cardiogenic shock or in the setting of a primary respiratory process complicated by diminished cardiac function. Cannulation is performed with venous drainage from the right femoral vein through a long cannula placed such that optimal drainage from the right atrium is achieved. Oxygenated blood is returned via femoral arterial cannula. Cannulas may be placed percutaneously in the ICU or a direct cut-down for access to the femoral vasculature. Blood via the axillary artery by direct anastomosis of a conduit facilitates ambulation. This strategy may be an important consideration in the conversion of ambulatory VV ECMO to VA ECMO as this configuration continues to allow ambulation.⁵

   
   
3. 
   

   AV ECMO/AVCO₂ removal. AV ECMO utilizes the patient’s native hemodynamics to drive flow through a low resistance gas exchange device, the goal being CO₂ removal. This configuration is most suited to those patients awaiting lung transplantation whose primary issue is severe CO₂ retention. Sometimes described as pumpless extracorporeal lung assist (pECLA), flow through the circuit is usually 15% to 20% of cardiac output, which limits its use for oxygenation. Central cannulation has also been described.^6,7

   
   
4. 
   

   Central cannulation refers to placement of ECMO cannulas via thoracotomy or sternotomy. This most commonly refers to placement of ECMO for failure to wean from cardiopulmonary bypass. The disadvantage is the need for full operating room support; however, the full array of ECMO options are available via the great vessels, and complications of peripheral cannulation are avoided.