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Key Features

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  • Onset of symptoms on day 1 of life

  • Hypoxia with poor response to high concentrations of inspired oxygen

  • Right-to-left shunts through the foramen ovale, ductus arteriosus, or both

  • Most often associated with parenchymal lung disease

  • There are three underlying pathophysiologic mechanisms

    • Vasoconstriction due to perinatal hypoxia related to an acute event such as sepsis or asphyxia

    • Prenatal increase in pulmonary vascular smooth muscle development, often associated with meconium aspiration syndrome

    • Decreased cross-sectional area of the pulmonary vascular bed associated with lung hypoplasia (eg, diaphragmatic hernia)

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Clinical Findings

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  • Characterized by onset on the first day of life, usually from birth

  • Respiratory distress is prominent, and PaO2 is usually poorly responsive to high concentrations of inspired oxygen

  • Many infants have associated myocardial depression with systemic hypotension

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Diagnosis

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  • Echocardiography reveals right-to-left shunting at the level of the ductus arteriosus or foramen ovale, or both

  • Chest radiograph may show lung infiltrates related to associated pulmonary pathology (eg, meconium aspiration or hyaline membrane disease)

  • If the majority of right-to-left shunting is at the ductal level, pre- and postductal differences in PaO2 and SaO2 will be observed

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Treatment

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  • First-line therapy includes oxygen and ventilation (to reduce pulmonary vascular resistance) and crystalloid infusions (10–30 mL/kg) to improve systemic pressure

  • Ideally, systolic pressure should be > 50–60 mm Hg

  • With compromised cardiac function, systemic vasopressors can be used as second-line therapy (eg, dopamine, 5–20 μg/kg/min; epinephrine 0.05–0.3 μg/kg/min; or both)

  • Pulmonary vasodilation can be enhanced using inhaled nitric oxide, at doses of 5–20 ppm

  • High-frequency oscillatory ventilation has proved effective in many of these infants, particularly those with severe associated lung disease, by improving lung expansion and recruitment

  • In cases in which conventional therapy is failing (poor oxygenation despite maximum support), extracorporeal membrane oxygenation (ECMO) is used

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