A 22-year-old woman delivers a baby at 29 weeks of gestation. Shortly after birth, the neonate becomes short of breath. The neonate is placed on a ventilator, but dies of respiratory insufficiency. The brain at autopsy is shown. Which of the following mechanisms of disease best explains this complication of respiratory distress syndrome (RDS) of the neonate?
|C.||Chronic passive congestion|
Correct answer : a Anoxic injury
The pathogenesis of RDS of the newborn is intimately linked to a deficiency of surfactant.
This material lowers the surface tension of the alveoli at low lung volumes and thereby prevents collapse (atelectasis) of the alveoli during expiration.
Atelectasis secondary to surfactant defi ciency results in perfused but not ventilated alveoli, a situation that leads to hypoxia and acidosis.
Intraventricular cerebral hemorrhage is a major complication of RDS. The periventricular germinal matrix in the newborn brain is particularly vulnerable to hemorrhage because the dilated, thin-walled veins in this area rupture easily.
The pathogenesis of this complication is believed to refl ect anoxic injury to the periventricular capillaries, venous sludging and thrombosis, and impaired vascular autoregulation.
Despite advances in neonatal intensive care, the overall mortality of RDS is about 15%, and one third of infants born before 30 weeks of gestational age die of this disorder. Although the other choices are associated with bleeding, they are unlikely causes of periventricular hemorrhage in a baby with RDS.