86 CONGENITAL DIAPHRAGMATIC HERNIA
Denis D. Bensard M.D., Richard J. Hendrickson M.D.

1. What is the most common type of congenital diaphragmatic hernia (CDH)?

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Congenital abnormalities of the diaphragm include a posterolateral defect (Bochdalek hernia), an anteromedial defect (Morgagni hernia), or the eventration (central weakening) of the diaphragm. The Bochdalek hernia is the most common variant and generally occurs on the left (80%). Approximately 20% occur on the right, and < 1% are bilateral.

2. What signs and symptoms suggest CDH?

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Neonatal respiratory distress is the most common manifestation of CDH caused by associated lung maldevelopment. At birth or shortly thereafter, the infant develops severe dyspnea, retractions, and cyanosis. On physical examination, breath sounds are diminished on the ipsilateral side, heart sounds can be heard more easily in the contralateral chest, and the abdomen is scaphoid because of the herniation of abdominal viscera into the chest. Mediastinal shift may result impairing venous return and cardiac output.

3. How is the diagnosis confirmed?

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A chest radiograph demonstrates multiple loops of air-filled intestine in the ipsilateral thorax. If a chest radiograph is obtained before entry of significant amounts of air into the bowel, a confusing pattern of mediastinal shift, cardiac displacement, and opacification of the hemithorax may be observed. Insertion of a nasogastric tube followed by repeat chest radiograph often demonstrates the tube (i.e., stomach) in the chest and confirms the diagnosis.

4. Are other anomalies associated with CDH?

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Fifty percent of infants with CDH have associated anomalies. Fewer than 10% of patients with multiple major concurrent anomalies survive. Excluding intestinal malrotation and pulmonary hypoplasia, cardiac anomalies (63%) are the most frequent, followed by genitourinary (23%), gastrointestinal (17%), central nervous system (14%), and other pulmonary (5%) anomalies.

5. What therapeutic measures should be initiated before transport or operation?

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Perhaps the easiest and most effective palliative intervention is decompression of the stomach with a nasogastric tube, which prevents further distention of the bowel and lung compression. Endotracheal intubation permits adequate ventilation and oxygenation. Ventilatory pressures are kept low (< 30 mmHg), and the infant is ventilated at a rapid rate (40-60 breaths/min) to avoid barotrauma. Venous access and fluid resuscitation complete preliminary resuscitation.

6. What is the “honeymoon period”?

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The honeymoon period describes the interval of time in which a neonate demonstrates adequate oxygenation and ventilation in the absence of maximal medical therapy. Regardless of subsequent deterioration, a honeymoon period suggests that pulmonary function is compatible with survival.
7. Describe the operative approach. Show answer

CDH results in a physiologic derangement of the lungs that is not reversed by surgical reconstruction of the diaphragm. Thus, repair of CDH is not a surgical emergency. The infant must be stabilized before surgical repair is attempted. A transabdominal approach allows reduction of the herniated abdominal viscera from the chest, repair of the diaphgramatic defect without obstructed vision or tension, correction of malrotation, and stretching of the abdominal cavity or creation of a ventral hernia with a prosthetic patch if the reduced viscera are not easily accomodated in the abdomen.

8. What is the most feared complication of diaphragmatic hernia?

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The most feared complication is persistent fetal circulation (PFC). In CDH, one or both lungs are hypoplastic, the pulmonary vascular bed is reduced, and the pulmonary arteries exhibit thickened muscular walls that are hyperreactive. Newborns with CDH are particularly prone to the development of pulmonary hypertension. PFC arises from a sustained increase in pulmonary artery pressure. Blood is shunted away from the lungs, and the unoxygenated blood is diverted to the systemic circulation (right-to-left shunt) through the patent ductus arteriosus and patent foramen ovale. PFC results in hypoxemia, profound acidosis, and shock. PFC is triggered by acidosis, hypercarbia, and hypoxia, all potent vasoconstrictors of the pulmonary circulation.

9. Is PFC correctable? If so, how?

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Yes. Various strategies are used to prevent or reverse PFC:

1. Monitoring: Oximetry or arterial sampling (preductal in the right upper extremity; postductal in the lower extremity) permits early detection of shunting of unoxygenated blood to the systemic circulation.
2. Ventilation: Hypercarbia is corrected by mechanical ventilation; adequate sedation; and, if necessary, pharmacologic paralysis.
3. Oxygenation: Hypoxemia is corrected by adequate ventilation and high concentrations of inspired oxygen (generally FiO2 = 100%).
4. Resuscitation: Metabolic acidosis is managed by restoring adequate tissue perfusion (intravenous fluids or blood, inotropes, and sodium bicarbonate).
5. Rescue: Salvage therapies include administration of pulmonary vasodilators via the ventilatory circuit (nitric oxide) or systemic circulation (priscoline, prostaglandin E2), high-frequency ventilation, and extracorporeal membrane oxygenation (ECMO).

10. What is the survival rate for patients with CDH?

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The overall survival rate is 60%. The major determinants of survival are the degree of pulmonary hypoplasia and associated major congenital anomalies. Among infants surviving the early newborn period without significant lung dysfunction, the survival rate approaches 100%.

11. Does in utero intervention have a role in the treatment of patients with CDH?

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To date, fetal surgery for CDH remains experimental. In a prospective trial reported in 1997, the results of intrauterine repair of CDH were compared with conventional postnatal surgery with similar outcome. The investigators concluded that because open fetal surgery does not improve survival or outcome, prenatally diagnosed CDH should be treated postnatally.

References
BIBLIOGRAPHY
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