I. BACKGROUND. Extracorporeal membrane oxygenation (ECMO) is the application of a modified cardiopulmonary bypass for neonates in cardiac or respiratory failure not responding to conventional measures or treatments.

ECMO has been offered to 35,000 neonates worldwide to date (Tables 39.1 and 39.2). The use of ECMO for neonatal respiratory failure began to decline in the late 1990s due to improved strategies of lung protective ventilation and has been more constant since 2000. Approximately 40 centers in the United States offer neonatal ECMO.

A. Respiratory failure. The indications for neonatal ECMO are (i) reversible respiratory failure and (ii) a predicted mortality with conventional therapy great enough to warrant the risks of ECMO. ECMO is also considered in patients with life-threatening air leaks not manageable with optimal ventilatory support and chest drainage.

1. Oxygenation index (OI) is a measure of the severity of respiratory failure and is calculated as follows: OI = mean airway pressure (MAP) × FiO₂/PaO₂ × 100. It is essential to document OIs from serial blood gases over time because the OI may vary. ECMO indications vary among different centers. Commonly used criteria include two OIs of >40 within 1 hour, one OI of 60 on high-frequency ventilation, or one OI of 40 combined with cardiovascular instability. For infants hospitalized where ECMO is not available, an OI of 20 should prompt early outreach to an ECMO center for potential transfer because prolonged ventilation at high ventilator settings may worsen ventilator-induced
lung injury and worsen the overall outcome. On a practical level, once ventilator support is maximally escalated, transport to an ECMO center may become impossible.

2. Total anomalous pulmonary venous return (TAPVR) may mimic neonatal respiratory distress syndrome (RDS), resulting from lung
congestion in the setting of inadequate drainage of the pulmonary veins in the left atrium. In any neonate with respiratory failure, hypoxia, and bilateral opacities on chest radiograph, TAPVR should be excluded prior to initiating ECMO support. Once venoarterial ECMO support is initiated, pulmonary blood flow is reduced and the diagnosis of TAPVR may be difficult to make using echocardiography alone; these patients may require cardiac catheterization on ECMO to demonstrate presence or absence of pulmonary veins entering the left atrium.

B. Cardiac failure. ECMO provides biventricular support for neonates with cardiac failure. General indications are low cardiac output (CO) syndrome despite maximal hemodynamic support or cardiac arrest with a potentially reversible underlying condition. ECMO for congenital heart defects can be offered as a bridge to definitive treatment until the newborn’s condition has stabilized. Other cardiac indications are failure to wean from cardiopulmonary bypass, cardiomyopathy, and pulmonary hypertension.

C. Rapid-response ECMO (ECMO-cardiopulmonary resuscitation [E-CPR]). In the setting of a witnessed cardiorespiratory arrest, ECMO can be offered in centers with a rapid response team. Response times from the arrest to cannulation are ideally 15 to 30 minutes. A readily “clear-primed circuit” (an ECMO circuit primed with normal saline rather than with blood products) and an ECMO team must be available 24 hours per day in order to offer E-CPR. Effective cardiopulmonary resuscitation (CPR) before cannulation is essential for a favorable outcome during rapid-response ECMO.

D. Ex utero intrapartum treatment (EXIT) to ECMO procedure. The vessels are cannulated during a cesarean section while the newborn remains on placental support. Indications include severe congenital diaphragmatic hernia (CDH), lung tumors, and airway obstructing lesions such as large neck masses and mediastinal tumors.

E. Contraindications. ECMO should only be offered for reversible conditions. Contraindications are considered to be lethal chromosomal disorder (including trisomies 13 and 18 but not 21), irreversible brain damage, and grade 3 or greater intraventricular hemorrhage (IVH) or intraparenchymal hemorrhage. Relative contraindications include weight <1,500 g due to cannula size limitations (except for thoracic cannulations), gestational age <34 weeks due to increased risk of IVH, severe coagulopathy, progressive chronic lung disease, and continuous CPR for more than an hour before ECMO support.

A. Flow. Venous drainage is passive from the patient to the ECMO circuit if nonocclusive roller pumps are used and active if centrifugal pumps are used. The cessation of venous drainage (due to cannula malposition, intravascular hypovolemia, cardiac tamponade, and pneumothorax) causes slowing of the pump speed because negative pressure could introduce air into the circuit. Flow is determined by venous return and the ECMO pump.

B. Venoarterial (VA) ECMO. VA ECMO supports the cardiac and the respiratory system and is indicated for primary cardiac failure or respiratory failure combined with secondary cardiac failure. In VA ECMO, the blood is
drained from a single vein (internal jugular vein, femoral vein) and returned into the arterial system (internal carotid artery). Venovenous-arterial ECMO indicates drainage from two different veins and return to the arterial side. The patient’s total CO is the sum of the native CO and the pump flow generated by the circuit: CO_total = CO_native + CO_circuit.

C. Venovenous (VV) ECMO. VV ECMO supports only the respiratory system and is indicated for isolated respiratory failure. VV ECMO refers to drainage from a single vein, VVV ECMO to drainage from two different veins. VV ECMO can also be considered in respiratory failure with hemodynamic instability, when hypotension and cardiovascular instability are thought to be caused by hypoxemia alone, because VV ECMO usually leads to rapid reversal of hypoxia and acidosis. VV ECMO spares accessing the carotid artery. Venovenous dual lumen (VVDL) refers to ECMO using specially designed double-lumen cannulas, providing drainage as well as return through different lumens of the same cannula. Some of the blood is immediately recirculated into the ECMO circuit. The rest of the oxygenated blood goes to the right side of the heart, into the pulmonary vascular bed, into the left side of the heart, and into the systemic circulation. As a requirement for VV ECMO, the internal jugular vein has to be large enough for a 14 French double-lumen cannula. Converting to VA ECMO is considered in the presence of additional hypotension, cardiac failure, or metabolic acidosis. Technical difficulties related to large recirculation in the venous cannula can also lead to the need to convert to VA ECMO. In our institution, the carotid artery is routinely identified at the time of VV cannulation. For conversion to VA ECMO, the venous cannula is left in place and an additional arterial cannula is inserted into the internal carotid artery.

D. Oxygen delivery. Oxygen delivery is the product of CO and arterial oxygen content. During ECMO, many factors contribute to oxygen delivery. Arterial oxygen content is determined by the gas exchange in the membrane oxygenator and the gas exchange from the neonate’s lung. CO is only altered during VA ECMO and is determined by the ECMO flow and the infant’s native CO.