Persistence of or reversion to pulmonary arteriolar constriction, causing a severe reduction in pulmonary blood flow and right-to-left shunting at the atrial and/or ductal level
Aetiology
More likely in sick babies - sepsis, hypoxic, meconium aspiration syndrome, cold stress
Can be related to an underlying anatomical abnormality e.g. congenital diaphragmatic hernia
Pathophysiology
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
Clinical features
Tachypnoea
Severe cyanosis which does not improve with administration of 100% oxygen
Investigations
Oximetry: significant difference in pre and post ductal saturations
Echocardiogram
Management
Oxygen to dilate pulmonary vasculature and improve oxygenation