Pulmonary hypertension of the newborn

Pulmonary hypertension presenting in the neonatal period can be due to congenital heart malformations (most commonly associated with obstruction to pulmonary venous drainage), high output cardiac failure from large arteriovenous malformations and persistent pulmonary hypertension of the newborn (PPHN). Of these, the most common cause is PPHN. PPHN develops when pulmonary vascular resistance (PVR) remains elevated after birth, resulting in right-to-left shunting of blood through foetal circulatory pathways. The PVR may remain elevated due to pulmonary hypoplasia, like that seen with congenital diaphragmatic hernia; maldevelopment of the pulmonary arteries, seen in meconium aspiration syndrome; and maladaption of the pulmonary vascular bed as occurs with perinatal asphyxia. These newborn patients typically require mechanical ventilatory support and those with underlying lung disease may benefit from high-frequency oscillatory ventilation or extra-corporeal membrane oxygenation (ECMO). Direct pulmonary vasodilators, such as inhaled nitric oxide, have been shown to improve the outcome and reduce the need for ECMO. However, there is very limited experience with other pulmonary vasodilators. The goals for anaesthetic management are (1) to provide an adequate depth of anaesthesia to ablate the rise in PVR associated with surgical stimuli; (2) to maintain adequate ventilation and oxygenation; and (3) to be prepared to treat a pulmonary hypertensive crisis--an acute rise in PVR with associated cardiovascular collapse.