Persistent Pulmonary Hypertension of the Newborn

The most common causes of persistent pulmonary hypertension of the newborn involve

A history of meconium staining of amniotic fluid or meconium in the trachea is common. Hypoxia triggers reversion to or persistence of elevated pulmonary vascular resistance, a normal state in the fetus.

Additional causes include

Whatever the cause, elevated resistance in the pulmonary arteries causes abnormal smooth muscle development and hypertrophy in the walls of the small pulmonary arteries and arterioles and right-to-left shunting via the ductus arteriosus or a foramen ovale, resulting in intractable systemic hypoxemia. Both pulmonary and systemic resistances are high, which leads to an increased load on the heart. This load increase may result in right heart dilation, tricuspid insufficiency, and right heart failure.

Symptoms and signs of persistent pulmonary hypertension of the newborn include tachypnea, retractions, and severe cyanosis or desaturation unresponsive to supplemental oxygen. In infants with a right-to-left shunt via a patent ductus arteriosus Patent Ductus Arteriosus (PDA) Patent ductus arteriosus (PDA) is a persistence of the fetal connection (ductus arteriosus) between the aorta and pulmonary artery after birth. In the absence of other structural heart abnormalities... read more , oxygenation is higher in the right brachial artery than in the descending aorta; thus cyanosis may be differential (ie, oxygen saturation in the lower extremities is ≥ 5% lower than in the right upper extremity).

Diagnosis of persistent pulmonary hypertension of the newborn should be suspected in any near-term infant with arterial hypoxemia, cyanosis, or both, especially one with a suggestive history whose oxygen saturation does not improve with administration of 100% oxygen.

Diagnosis is confirmed by echocardiogram, which can confirm the presence of elevated pressures in the pulmonary artery and simultaneously can exclude congenital heart disease.

Blood cultures should be done because prenatal infection is a possible cause of persistent pulmonary hypertension in the newborn.

On x-ray, lung fields may be normal or may show changes due to the underlying disorder (eg, meconium aspiration syndrome Meconium Aspiration Syndrome Intrapartum meconium aspiration can cause inflammatory pneumonitis and mechanical bronchial obstruction, causing a syndrome of respiratory distress. Findings include tachypnea, rales and rhonchi... read more , neonatal pneumonia Diagnosis Neonatal pneumonia is lung infection in a neonate. Onset may be within hours of birth and part of a generalized sepsis syndrome or after 7 days and confined to the lungs. Signs may be limited... read more , congenital diaphragmatic hernia Diagnosis Diaphragmatic hernia is protrusion of abdominal contents into the thorax through a defect in the diaphragm. Lung compression may cause persistent pulmonary hypertension. Diagnosis is by chest... read more ). X-ray abnormalities may be difficult to distinguish from bacterial pneumonia.

The oxygenation index (mean airway pressure [cm H2O] × fraction of inspired oxygen [FIO2] × 100/PaO2) is used to assess disease severity and determine timing of interventions (in particular for inhaled nitric oxide [oxygenation index 15 to 25] and extracorporeal membrane oxygenation [ECMO—oxygenation index > 40]).

Overall mortality ranges from 10 to 60% and is related to the underlying disorder. However, 25% of survivors exhibit developmental delay, hearing deficits, functional disabilities, or a combination. This rate of disability may be no different from that of other infants with severe illness.

Treatment with oxygen, which is a potent pulmonary vasodilator, is begun immediately to prevent disease progression. Oxygen is delivered via bag-and-mask or mechanical ventilation Mechanical Ventilation Initial stabilization maneuvers include mild tactile stimulation, head positioning, and suctioning of the mouth and nose followed as needed by Supplemental oxygen Continuous positive airway... read more ; mechanical distention of alveoli aids vasodilation. FIO2 should initially be 1 but can be titrated downward to maintain PaO2 between 50 and 90 mm Hg to minimize lung injury. Once PaO2 is stabilized, weaning can be attempted by reducing FIO2 in decrements of 2 to 3%, then reducing ventilator pressures; changes should be gradual, because a large drop in PaO2 can cause recurrent pulmonary artery vasoconstriction. High-frequency oscillatory ventilation expands and ventilates the lungs while minimizing barotrauma and should be considered for infants with underlying lung disease in whom atelectasis and ventilation/perfusion (V/Q) mismatch may exacerbate the hypoxemia of persistent pulmonary hypertension of the newborn.

Inhaled nitric oxide relaxes endothelial smooth muscle, dilating pulmonary arterioles, which increases pulmonary blood flow and rapidly improves oxygenation in as many as half of patients. Initial dose is 20 ppm, titrated downward by effect.

ECMO Extracorporeal Membrane Oxygenation (ECMO) Initial stabilization maneuvers include mild tactile stimulation, head positioning, and suctioning of the mouth and nose followed as needed by Supplemental oxygen Continuous positive airway... read more may be used in newborns with severe hypoxic respiratory failure defined by an oxygenation index > 35 to 40 despite maximum respiratory support.

Normal fluid, electrolyte, glucose, and calcium levels must be maintained. Infants should be kept in a neutral thermal environment and treated with antibiotics for possible sepsis until culture results are known. Inotropes and pressors may be required as part of circulatory support.