Anemia of Prematurity - Portal Neonatal

The components of pulmonary surfactant are synthesized in the Golgi apparatus of the
endoplasmic reticulum of the type II alveolar cell (see Image 5). The components are packaged in
multilamellar vesicles in the cytoplasm of the type II alveolar cell and are secreted by a process of
exocytosis, the daily rate of which may exceed the weight of the cell. Once secreted, the vesicles
unwind to form bipolar monolayers of phospholipid molecules that are dependent on the
apoproteins SP-B and SP-C to configure properly in the alveolus. The lipid molecules are enriched
in dipalmitoyl acyl groups attached to a glycerol backbone that pack tightly and generate low
surface pressures.
Tubular myelin stores surfactant and may depend on SP-B. Corners of the myelin lattice appear to
be glued together with the larger apoprotein SP-A, which may also have an important role in
phagocytosis. Hypoxia, acidosis, hypothermia, and hypotension may impair surfactant production
and/or secretion of surfactant.
Frequency:
• In the US: While the greatest risk factor for developing RDS is prematurity, maternal
diabetes and asphyxia are also risk factors. Not all premature infants develop RDS.
Approximately half of infants born at 28-32 weeks' gestation develop RDS.
In the United States, RDS occurs in approximately 40,000 infants each year and in 14% of
low birth weight infants. Incidence of RDS increases with decreasing gestational age and
may occur in as many as 45-80% of infants born when younger than 28 weeks' gestation.
• Internationally: RDS has been reported in all races worldwide, occurring more often in
premature infants of Caucasian ancestry.
History:
CLINICAL Section 3 of 11
• RDS frequently occurs in the following individuals:
o Male infants
o Infants born to mothers with diabetes
o Infants delivered via cesarean without maternal labor
o Second-born twins
o Infants with a family history of RDS
• In contrast, the incidence of RDS decreases with the following:
o Use of antenatal steroids
o Pregnancy-induced or chronic maternal hypertension
o Prolonged rupture of membranes
o Maternal narcotic addiction
• Secondary surfactant deficiency may occur in infants with the following:
o Intrapartum asphyxia
o Pulmonary infections
o Pulmonary hemorrhage
o Meconium aspiration pneumonia
o Oxygen toxicity along with barotrauma or volutrauma to the lungs