Neonatal Congenital Diaphragmatic Hernia: ECMO Criteria

Neonatal congenital diaphragmatic hernia (CDH) is a structural defect in the diaphragm that permits abdominal organs to enter the chest. The resulting compression of the developing lungs can cause pulmonary hypoplasia, while abnormal pulmonary vascular development may produce severe pulmonary hypertension. Respiratory failure in these infants is therefore driven by more than an isolated airway problem.

Extracorporeal membrane oxygenation (ECMO), often called extracorporeal life support (ECLS), may support selected newborns when conventional treatment cannot maintain adequate oxygen delivery. The decision is complex because ECMO carries substantial risks, and the underlying lung hypoplasia cannot be reversed by extracorporeal support.

A careful assessment combines trends in oxygenation, ventilation, circulation, echocardiography, neurologic status, gestational age, birth weight, bleeding risk, and the experience of the treating center. Fixed numbers can guide escalation, but they should not replace repeated bedside evaluation or consultation with a neonatal ECMO team.

Why CDH Can Lead To Refractory Failure

The central physiologic problem in severe CDH is the combination of small lungs and high pulmonary vascular resistance. A newborn may receive an apparently adequate fraction of inspired oxygen while still developing profound preductal hypoxemia because blood continues to bypass the lungs through the ductus arteriosus or foramen ovale.

Mechanical ventilation can worsen this situation if high pressures overdistend the better-developed lung. Excessive airway pressure may increase lung injury, impair venous return, and raise pulmonary vascular resistance. For this reason, modern stabilization generally favors gentle ventilation, permissive hypercapnia within an acceptable pH range, and avoidance of routine aggressive bag-mask ventilation.

Pulmonary hypertension may fluctuate rapidly. A baby can improve after sedation, correction of acidosis, treatment of pneumothorax, or optimization of cardiac preload, then deteriorate again. ECMO evaluation should begin before irreversible cardiovascular collapse, especially when oxygenation and perfusion remain poor despite lung-protective management.

When Conventional Support Is No Longer Enough

Initial care commonly includes endotracheal intubation, gastric decompression, low-pressure ventilation, analgesia and sedation, careful fluid management, and correction of hypoglycemia, hypothermia, anemia, and metabolic acidosis. Echocardiography helps identify pulmonary hypertension, right ventricular dysfunction, left ventricular impairment, structural heart disease, and ductal shunting patterns.

Inhaled nitric oxide can be useful when pulmonary hypertension is a major contributor, particularly when there is evidence of adequate left ventricular function and recruitable pulmonary vasculature. Its response should be assessed objectively rather than assumed. Vasoactive medications may support systemic pressure and cardiac output, but increasing blood pressure alone does not guarantee improved pulmonary blood flow or oxygen delivery.

A neonate who remains severely hypoxemic, acidotic, or poorly perfused despite optimized treatment should be referred early for ECMO consideration. Waiting until prolonged cardiac arrest, severe organ injury, or uncontrolled acidosis has developed can reduce the likelihood of a favorable outcome. The referral discussion should occur while cannulation remains technically and physiologically feasible.

Interpreting Oxygenation And Perfusion Markers

The oxygenation index (OI) is frequently used to quantify the intensity of respiratory support required:

OI = mean airway pressure × fraction of inspired oxygen × 100 ÷ postductal arterial oxygen tension

An OI persistently above 40 is a widely recognized threshold for considering ECMO in neonatal respiratory failure. In CDH, however, clinicians often examine the trajectory and duration of the rise rather than reacting to a single measurement. A rapidly increasing OI, severe preductal desaturation, and worsening lactate may justify urgent action even before a formal threshold is sustained.

Preductal saturation, usually measured on the right hand, provides a useful estimate of oxygen delivery to the upper body. A substantial and persistent difference between preductal and postductal saturation can indicate right-to-left ductal shunting. Arterial blood gas results, pH, lactate, urine output, capillary refill, blood pressure, and mixed venous oxygen measures add important information about the adequacy of systemic perfusion.

These measures should be interpreted together. A high OI with stable lactate and preserved ventricular function is different from a moderate OI accompanied by shock and escalating vasoactive support. Conversely, a deceptively acceptable arterial oxygen value may coexist with poor tissue oxygenation when cardiac output is low.

Establishing Candidacy For Extracorporeal Support

ECMO candidacy is based on expected benefit, reversibility, and the safety of anticoagulation and cannulation. Severe but potentially reversible pulmonary hypoplasia and pulmonary hypertension may be appropriate indications. The team must also consider whether the infant has adequate neurologic potential, manageable cardiac anatomy, and sufficient size and maturity for the available circuit and cannulation approach.

Before proceeding, clinicians should search for reversible explanations for deterioration. Pneumothorax, misplaced endotracheal tube, mucus obstruction, inadequate sedation, sepsis, hypovolemia, severe anemia, arrhythmia, and left ventricular failure can all mimic worsening pulmonary disease. Echocardiography is particularly valuable because CDH physiology may include both right-sided and left-sided cardiac compromise.

Absolute and relative contraindications vary among programs and evolve with technology. Common concerns include major uncontrolled intracranial hemorrhage, lethal chromosomal or structural abnormalities, irreversible multiorgan failure, extreme prematurity, very low birth weight, and prolonged high-quality cardiopulmonary resuscitation with evidence of severe injury. None should be applied without considering the individual infant and the resources of the ECMO center.

The mode of support also matters. Venoarterial ECMO can provide both respiratory and circulatory support, making it the usual option when pulmonary hypertension, ventricular dysfunction, or shock is prominent. Venovenous ECMO may preserve native cardiac function and avoid arterial cannulation in carefully selected infants, but it requires adequate cardiac performance and may be less suitable when cardiovascular failure is central.

Timing, Cannulation, And Surgical Planning

The most useful ECMO decision is often made before a crisis. A multidisciplinary team should establish an escalation plan during the first hours of stabilization, including thresholds for bedside reassessment, transfer, anticoagulation review, and cannulation. This plan should be communicated to neonatology, pediatric surgery, cardiology, anesthesiology, perfusion, nursing, and the family.

CDH repair is generally delayed until the infant has achieved physiologic stability rather than performed as an emergency response to respiratory failure. Stabilization targets may include improving pulmonary pressures, acceptable gas exchange on gentle ventilator settings, adequate urine output, stable blood pressure, and controlled lactate. If ECMO is required, the timing of repair depends on institutional practice, bleeding risk, the degree of cardiopulmonary dependence, and the infant’s response to support.

Anticoagulation makes surgery and invasive procedures more hazardous. Cannulation itself can produce bleeding, vascular injury, neurologic complications, and hemodynamic instability. The team therefore weighs the danger of waiting against the risks of initiating ECMO, with serial cranial imaging and coagulation monitoring forming part of the broader safety strategy.

Outcome prediction remains imperfect. Prenatal liver position, observed-to-expected lung-to-head ratio, pulmonary vein development, cardiac function, and postnatal response to stabilization can help describe disease severity, but no single variable determines an individual infant’s outcome. Families should receive clear information about uncertainty, possible duration of support, surgical timing, and the potential for long-term respiratory, neurologic, and developmental needs.

Managing The Infant After ECMO Initiation

Once ECMO begins, the objective is to provide adequate oxygen delivery while allowing the lungs to rest and recover. Ventilator settings are commonly reduced to limit barotrauma and volutrauma, while the circuit supplies gas exchange. Hemodynamic management continues because ECMO does not eliminate pulmonary hypertension, right ventricular dysfunction, sepsis, or impaired left ventricular filling.

Monitoring includes circuit flow, oxygenator performance, blood gases, hemolysis, anticoagulation, platelet count, fibrinogen, renal function, liver function, neurologic examinations, and serial imaging. The team also watches for complications such as intracranial bleeding, thromboembolism, infection, limb ischemia, arrhythmia, and mechanical failure.

Weaning is considered when pulmonary vascular resistance falls, ventricular function improves, gas exchange becomes manageable with low ventilator support, and the infant maintains adequate perfusion with reduced ECMO flow. A trial-off assessment should be systematic and may include echocardiography, blood gas analysis, hemodynamic review, and evaluation of lung compliance. Persistent severe pulmonary hypertension or cardiac dysfunction may signal that decannulation is premature.

Practical Priorities For The Care Team

The best decisions are made through repeated, coordinated assessments rather than a single oxygenation value. Teams developing local protocols can use the following priorities:

• Begin ECMO consultation early when oxygenation, ventilation, or perfusion is deteriorating despite lung-protective stabilization.
• Track preductal saturation, oxygenation index, arterial pH, lactate, urine output, vasoactive requirements, and echocardiographic findings as a pattern.
• Correct reversible causes of decompensation before cannulation, including airway problems, pneumothorax, anemia, hypovolemia, infection, and ventricular dysfunction.
• Discuss gestational age, birth weight, neurologic imaging, congenital anomalies, anticoagulation risk, and expected reversibility with the full multidisciplinary team.
• Coordinate ECMO timing with pulmonary hypertension management and delayed surgical repair rather than treating each decision in isolation.

Perinatal medicine depends on shared terminology, careful outcome reporting, and communication across centers. The scientific environment surrounding these questions includes neonatal respiratory failure, fetal lung development, pulmonary vascular biology, pediatric surgery, and extracorporeal technology; the FAOPS 2020 congress site reflects the wider professional setting in which such topics are discussed.

For clinicians and institutions, the next step is to review local CDH pathways against current ECMO capabilities, define escalation triggers before emergencies occur, and ensure that families receive timely, comprehensible counseling. Early recognition and organized referral cannot remove the severity of pulmonary hypoplasia, but they can preserve options when extracorporeal support may offer the infant a meaningful chance to recover.