Medications for Persistent Pulmonary Hypertension of the Newborn

Persistent pulmonary hypertension of newborn (PPHN) results from the unsuccessful transition at birth of the fetus getting oxygenated blood from the mother (the antenatal circulation) to when it is born and the baby is oxygenating its own blood using the systemic circulation and pulmonary circulation.

Transition of a baby’s circulation:

Before a baby is born it receives oxygenated blood from the placenta, which flows to the umbilical vein, then to the heart’s right atrium and it is then diverted through the foramen ovale to the heart’s left atrium.

 At birth the the baby needs to establish the lungs as the site of blood oxygenation. Respiration induces various changes that causes widening of lung blood vessels (a decrease in pulmonary vascular resistance) which dramatically increases the blood flow through the baby’s lungs. As the placenta is no longer part of the circulation there is a increase in pressure of the baby’s systemic circulation (systemic vascular resistance) which results in a decrease in blood flow from right atrium to left atrium enough to cause closure of the foramen ovale.

Signs and Causes:

Failure of conversion from the antenatal circulation to the postnatal circulation at birth results in PPHN which is identified by high pulmonary vascular resistance, decrease pulmonary blood flow, right to left shunting of the blood in the heart, and results in large swings in arterial oxygen saturation levels (labile hypoxemia).
PPHN can be caused a number of problems including parenchymal disorders (eg meconium aspiration and pneumonia), intravascular obstruction, pulmonary hypertension in preterm infants, abnormal lung development or abnormal transition in birth.