Extracorporeal membrane oxygenation (ECMO) is a prolonged form of extracorporeal life support used to treat neonates with life-threatening respiratory or cardiac disorders who fail to respond to maximal medical management. Extracorporeal life support (ECLS) is a term used synonymously with ECMO though it often implies a broader array of functions that may include oxygen delivery, carbon dioxide elimination, cardiac support, or combinations of these functions.
Disorders treated with ECMO
Respiratory diseases (Table 33-1)
The neonatal respiratory disorders most commonly treated with ECMO cause hypoxemic respiratory failure that is often complicated by persistent pulmonary hypertension of the newborn; such disorders include meconium aspiration syndrome, congenital diaphragmatic hernia, sepsis/pneumonia, primary persistent pulmonary hypertension, and air leaks.
Respiratory distress syndrome accounted for a significant number of ECMO cases in the 1980s but this number has declined with the introduction of exogenous surfactant treatment in 1990. Furthermore, the introduction of inhaled nitric oxide and high-frequency mechanical ventilator devices and strategies in the mid-1990s has been associated with a significant decline in number of neonatal respiratory failure cases receiving ECMO.
The peak number of neonatal respiratory ECMO cases reported to an international registry maintained by the Extracorporeal Life Support Organization was 1516 in 1992; there were 801 neonatal respiratory cases reported in 2011.
As a consequence, neonatal cases treated with ECMO are more often than not sicker than in the 1980s and 1990s, not responsive to advances in care (such as surfactant, inhaled nitric oxide, high-frequency ventilation, and gentle ventilation strategies), and have less frequently encountered disorders associated with hypoxemic respiratory failure such as surfactant protein deficiencies, alveolar capillary dysplasia, and pulmonary interstitial glycogenosis.
Cardiac diseases (Table 33-2)
The neonatal cardiac disorders most commonly treated with ECMO are predominantly hypoplastic left heart syndrome and other complex congenital disorders; anomalous pulmonary venous return, disorders with decreased pulmonary blood flow, and left-sided obstructive lesions account for a substantial number of ECMO cases.
Most neonatal ECMO cases involving cardiac disorders receive ECMO following surgery because of poor cardiac function after cardiopulmonary bypass and/or a pulmonary hypertensive crisis, usually presenting within 24 hours of surgery. Advances in cardiac surgery that involve complex surgical procedures with ECMO as an adjunct treatment have contributed to an increase in the numbers of neonatal ECMO cases having congenital cardiac disorders rather than respiratory illnesses.
The number of neonatal cardiac ECMO cases grew from 104 in 1992 to 374 in 2011.
Pathophysiology: how ECMO works
Historical highlights of ECMO
Initial experiences in treating neonates in the 1970s and early 1980s led to widespread dissemination by the beginning of the 1990s. Investigators in the United Kingdom performed a randomized trial comparing ECMO to conventional treatment in the mid-1990s and proved that ECMO significantly increases survival in high-risk neonates without increasing morbidity. Death or severe disability in the ECMO treated cases was 33% versus 62% in the conventionally treated control group.
ECMO circuit (Figure 33-1)
Components: The essential ...
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