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At a glance

A congenital disorder with underdevelopment of one or both lungs.

Incidence

Estimated to be in the range of 9-11:10,000 live births (for primary and secondary pulmonary hypoplasia combined). Primary Congenital Pulmonary Hypoplasia (CPH) is much rarer.

Genetic inheritance

Autosomal recessive inheritance has been suggested; however, most cases appear to be sporadic. Pulmonary hypoplasia occurs significantly more often secondary to other intrauterine anomalies.

Diagnosis

Primary CPH is defined as quantitative and/or qualitative underdevelopment of bronchial and pulmonary structures unrelated to other maternal or fetal disorders (eg, congenital diaphragmatic hernia, oligohydramnios). Small clear lungs on chest x-ray, early development of pneumothoraces (even when breathing spontaneously), bell-shaped chest, and bilaterally raised diaphragms are considered diagnostic radiologic features for CPH. One fetal ultrasound case report found hypoplastic branch pulmonary arteries with decreased flow and increased cardiothoracic diameter ratios, which was considered diagnostic for CPH and confirmed by autopsy after termination of the pregnancy. Depending on the severity, the reported mortality rate is up to 95%. Autopsy usually reveals pulmonary hypoplasia with a reduction in the number of large and small bronchi, bronchioles, and alveoli, which may be lined by hypoplastic and slightly atypical Type II pneumocytes. The connective tissue septae may appear thickened. The normal lung-to-birth weight ratio is greater than 1.2%, and a reduced ratio of less than or equal to 0.9% makes CPH very likely. A lung weight below 50% of normal is almost always lethal. However, secondary (ventilator-induced) lung changes may result in increased lung weight. Hypotheses with regard to the underlying cause include an arrest in the development of the bronchial tree, a defect in the differentiation of the mesodermal bud, a general delay in lung maturation, or normally differentiated, but small lungs.

Clinical aspects

CPH is extremely rare and more commonly, pulmonary hypoplasia occurs secondary to other anomalies, such as intrauterine compression of the developing lungs (diaphragmatic hernia, tumor, pleural effusion, skeletal anomalies, tracheobronchial stenosis), oligohydramnios, or impaired fetal breathing movements secondary to agenesis of the phrenic nerve or neuromuscular diseases. The compressive lesions may lead to unilateral hypoplasia, while systemic causes and CPH most often result in bilateral hypoplasia, which is generally lethal shortly after birth. Respiratory distress usually manifests within the first 5 minutes after birth, which is also reflected in the Apgar scores. Mechanical ventilation with high oxygen concentrations and ventilator pressures are required to initially maintain reasonable arterial saturations. Nevertheless, most infants deteriorate further and die of respiratory failure (on average 9 hours after birth). Only a few infants have survived and were eventually discharged home from the hospital.

Precautions before anesthesia

The most likely scenario would be that the anesthesiologist is called to help with initial resuscitation attempts, thus there is not enough time for a thorough systems review. ...

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