Abstract
Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation at birth due to delay or impairment in the normal fall in pulmonary vascular resistance (PVR) that occurs following birth. The fetus is in a state of physiological pulmonary hypertension. In utero, the fetus receives oxygenated blood from the placenta through the umbilical vein. At birth, following initiation of respiration, there is a sudden precipitous fall in the PVR and an increase of systemic vascular resistance (SVR) due to the removal of the placenta from circulation. There is dramatic increase in pulmonary blood flow with a decrease in, and later reversal of shunts at the foramen ovale and ductus arteriosus. The failure of this normal physiological pulmonary transition leads to the syndrome of PPHN. PPHN presents with varying degrees of hypoxemic respiratory failure. Survival of infants with PPHN has significantly improved with the use of gentle ventilation, surfactant and inhaled nitric oxide (iNO). PPHN is associated with significant mortality and morbidity among survivors. Newer agents that target different enzymatic pathways in the vascular smooth muscle are in different stages of development and testing. Further research using these agents is likely to further reduce morbidity and mortality associated with PPHN.
Highlights
During fetal life, pulmonary vascular resistance (PVR) is high and pulmonary blood flow (Qp) is low [1]
Survival of infants with pulmonary hypertension of the newborn (PPHN) has significantly improved with the use of gentle ventilation, surfactant and inhaled nitric oxide
The failure of this normal physiological pulmonary transition leads to the syndrome of PPHN often manifesting as hypoxic respiratory failure (HRF)
Summary
Pulmonary vascular resistance (PVR) is high and pulmonary blood flow (Qp) is low [1]. PVR decreases and Qp increases at birth [2]. Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of failed circulatory adaptation due to the delay or impairment of the normal fall in PVR that occurs following birth [3]. PPHN is associated with significant mortality and morbidity among survivors. The incidence of PPHN is 1.8 to 2 per 1000 births [4,5] and about 2% in premature infants with respiratory distress syndrome (RDS)
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