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Objectives
Discuss the historical development of extracorporeal gas exchange and the future use of extracorporeal gas exchange.
Compare the advantages and disadvantages of venovenous (VV) and venoarterial (VA) extracorporeal gas exchange.
Discuss the advantages and problems associated with the different pumps types, oxygenators, and catheters used for ECLS.
Discuss the circumstances in which extracorporeal CO2 elimination may be used.
Discuss the indication for the use of ECMO in neonates, pediatrics, and adults.
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The concept of extracorporeal life support (ECLS, commonly called extracorporeal membrane oxygenation [ECMO]) has been available since the introduction of cardiac bypass during cardiac surgery. The first use of ECMO outside of the operating room occurred in the late 1960s. These first applications were to patients with severe refractory hypoxemia and the acute respiratory distress system (ARDS). Based on the initial successful application of ECMO to patients with ARDS in the 1970s, a randomized controlled trial comparing the use of ECMO to standard conventional management in patients with ARDS was conducted. This study failed to show benefit for the use of ECMO, with mortality in each group of about 90%. As a result, the use of ECMO in adult ARDS was not considered an option by most centers. In the 1980s a number of groups began using neonatal ECMO in an attempt to reduce the mortality in near-term infants from meconium aspiration, diaphragmatic hernia, sepsis, pneumonia, and other causes of severe respiratory failure. By the 1990s, based on the success of ECMO in neonates, more centers began using ECMO in pediatric and adult patients with severe respiratory failure. By 2000, the use of ECMO expanded to cardiac patients in all age groups. The increased use of ECMO in ARDS has been supported in recent years by the successful use of ECMO in the H1N1 epidemic of 2009. Today, ECMO is also used as a bridge to lung and heart transplantation and as a means of ensuring lung protective ventilation in patients in whom CO2 elimination is markedly compromised.
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Types of Extracorporeal Life Support
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There are two approaches to ECLS: VV and VA. With VV ECMO, blood is removed from a major vein, passed through a pump and oxygenator, and back to the patient via a major vein. In VA ECMO, blood is removed from a major vein but, after passing through a pump and oxygenator, is returned via a major artery.
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This approach to ECMO is primarily designed to support the respiratory system. Blood is removed from a large vein, usually a femoral vein with the catheter frequently extending into the inferior vena cava, and returned to another large vein, the contralateral femoral or the superior vena cava via the jugular vein (Figure 38-1). Since the arterial circulation is not affected, normal pulsatile blood flow is maintained. This approach requires a normal functioning heart. Thus, blood flows ...