Laboratory Studies
Several studies may be indicated in congenital diaphragmatic hernia (CDH).
Obtain frequent ABG measurements to assess for pH, PaCO2, and PaO2. Note the sampling site because persistent pulmonary hypertension of the newborn (PPHN) with right-to-left ductal shunting often complicates CDH. The PaO2 is often higher from a preductal (right-hand) sampling site.
Serum lactate may be helpful in assessing for circulatory insufficiency or severe hypoxemia associated with tissue hypoxia.
Obtain chromosome studies, including microarray analysis, because of the frequent association with chromosomal anomalies. In rare cases (eg, Pallister-Killian syndrome), chromosomal disorders that can be diagnosed only based on skin biopsy findings may be present. If dysmorphic features are observed upon examination, a consultation with a geneticist is often helpful in evaluating the infant and ensuring that chromosome studies include appropriate deletion analysis.
As with all critically ill neonates, monitor levels of serum electrolytes, ionized calcium, and glucose initially and frequently. Maintaining glucose levels in the reference range and maintaining calcium homeostasis are particularly important.
Continuous pulse oximetry is also valuable in the diagnosis and management of PPHN. Place oximeter probes at preductal (right-hand) and postductal (either foot) sites to assess for a right-to-left shunt at the ductus arteriosus level.
Imaging Studies
Obtain a chest radiograph if congenital diaphragmatic hernia is suspected (see the image below).
Pediatric Congenital Diaphragmatic Hernia. Radiograph of a 1-day-old infant with a moderate-sized congenital diaphragmatic hernia (CDH). Note the air- and fluid-filled bowel loops in the left chest, the moderate shift of the mediastinum into the right chest, and the position of the orogastric tube.
Placement of an orogastric tube prior to the study helps decompress the stomach and helps determine whether the tube is positioned above or below the diaphragm.
Typical findings in a left-sided posterolateral congenital diaphragmatic hernia include air-filled or fluid-filled loops of the bowel in the left hemithorax and shift of the cardiac silhouette to the right. Examine the chest radiograph for evidence of pneumothorax.
The incidence of associated cardiac anomalies is high (approximately 25%); therefore, cardiac ultrasonography is needed shortly after birth. Cardiac defects may be relatively minor (atrial septal defect) or life-threatening (transposition of great vessels, hypoplastic left heart, aortic coarctation). In addition, echocardiography is helpful in assessing myocardial function and determining whether the left ventricular mass is significantly decreased.
Genitourinary anomalies occur in 6-8% of infants with congenital diaphragmatic hernia; renal ultrasonography should be considered.
CNS defects (neural tube defects, hydrocephalus) may be associated with congenital diaphragmatic hernia. Although MRI provides definitive diagnostic information, bedside cranial sonography is generally performed when an infant is considered for extracorporeal support. In that circumstance, the goal is to evaluate for intraventricular bleeding and hypoxic-ischemic changes, as well as to rule out major intracranial anomalies.
Procedures
Endotracheal intubation and mechanical ventilation are required in all infants with severe congenital diaphragmatic hernia who present in the first hours of life. If the diagnosis is known at the time of delivery, avoid bag-and-mask ventilation in the delivery room because the stomach and intestines become distended with air and further compromise pulmonary function. A nasogastric tube should be placed as soon as possible to provide intestinal decompression.
As discussed in Treatment, the goal is to adequately expand the lung but to avoid overdistension; therefore, inspiratory pressures should be kept as low as possible. Consider the use of high-frequency ventilation (HFV) if high inspiratory pressures are required.
Place an indwelling catheter in the umbilical artery or in a peripheral artery (radial, posterior tibial) for continuous blood pressure and frequent ABG monitoring.
Place a venous catheter via the umbilical vein to allow for administration of inotropic agents and hypertonic solutions such as calcium gluconate. If the liver is in the chest, the catheter will likely not pass through the ductus venosus, and another route must be considered for central venous access.
The use of HFV in congenital diaphragmatic hernia remains controversial, and no randomized studies indicate a clear benefit. However, HFV may allow for use of lower ventilator pressures and may help normalize PaCO2. Mean airway pressures should be carefully adjusted to avoid lung overdistension. Frequent radiograph (with a goal of 8-9 rib expansion of the contralateral lung) may help in the ongoing assessment and optimization of lung expansion.
Venoarterial or venovenous ECMO support is an adaptation of cardiopulmonary bypass and involves a surgical team [17] ; insertion of catheters into the internal jugular vein, internal carotid artery, or both; systemic heparinization; and oxygenation through the use of an artificial membrane lung. Because of its complexity and resource expense, ECMO is available at fewer than 100 centers in the United States. The overall survival rate for infants with congenital diaphragmatic hernia reported to the international Extracorporeal Life Support Organization (ELSO) registry is approximately 52%, which is the lowest rate in all the neonatal conditions treated with ECMO. Although no conclusive evidence shows that ECMO improves survival or outcome for infants with congenital diaphragmatic hernia, it remains a commonly used therapy for severely affected infants.
Histologic Findings
Both lungs appear abnormal, although histologic changes are more severe on the affected side. Bronchi are less numerous, and the overall number of alveoli is reduced.
In addition, the lungs appear to be less mature with fewer mature alveoli. Pulmonary vascular abnormalities occur in addition to parenchymal abnormalities, characterized by both a reduction in the cross-sectional area of the pulmonary vascular bed and an abnormal increase in muscularization of pulmonary arteries and arterioles.
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Pediatric Congenital Diaphragmatic Hernia. Radiograph of a 1-day-old infant with a moderate-sized congenital diaphragmatic hernia (CDH). Note the air- and fluid-filled bowel loops in the left chest, the moderate shift of the mediastinum into the right chest, and the position of the orogastric tube.
