Diseases of Infancy and Childhood: Prematurity, neonatal respiratory distress syndrome, necrotizing enterocolitis Flashcards
what is prematurity defined as?
gestational age less than 37 weeks
What are the 4 risk factors for prematurity?
preterm premature rupture of membranes (PPROM), intrauterine infection, uterine/cervix/placental abnormalities, and multiple gestation
what is the major cause of preterm labor and what is an example of this?
intrauterine infection- funisitis (infection of the umbilical cord)
What are the 4 major hazards associated with prematurity?
RDS, NEC, sepsis, and intraventricular and germinal matrix hemorrhage
what is fetal growth restriction and how is this different than preterm infants?
infants who weigh less than 2500 grams (5.5 lbs) who are born at term are considered undergrown rather than immature; preterm infants usually have appropriate weight once adjusted for their gestational age
what are small for gestational age (SGA) infants at risk for?
struggle for survival in the perinatal period, but also in childhood and adult life; significant risk of morbidity in the form of major handicap, cerebral dysfunction, learning disability, or hearing/ visual impairment
what is the most common cause of respiratory distress in the newborn?
neonatal respiratory distress syndrome (RDS)
what is another name for respiratory distress syndrome?
hyaline membrane disease
who is at risk for having RDS?
premature neonates
what is the fundamental defect in RDS?
pulmonary immaturity and deficiency of surfactant
what is surfactant produced by?
type II alveolar cells- this becomes accelerated after the 35th week of gestation in the fetus
surfactant synthesis is modulated by a variety of hormones and growth factors including what?
cortisol, insulin, prolactin, thyroxine, and TGF-beta
what happens with a deficiency of surfactant?
the lungs collapse with each successive breath, so infants must work as hard with each successive breath as they did with the first
what is the problem with stiff atelectatic lungs compounded by?
the soft thoracic wall that is pulled in as the diaphragm descends
what chain of events follow atelectasis?
uneven perfusion and hypoventilation –> hypoxemia and CO2 retention; this leads to acidosis, which leads to pulmonary vasoconstriction, which leads to further pulmonary hypoperfusion; this ultimately leads to endothelial and epithelial damage, which causes the plasma to leak into the alveoli–> fibrin +necrotic cells (hyaline membrane)
what is the etiology of RDS?
prematurity
what are the associations of RDS?
male gender, maternal diabetes, and cesarean delivery
what does control of RDS focus on?
prevention- either by delaying labor until the fetal lung reaches maturity or by inducing maturation of the lung in the at risk fetus by use of steroids
on radiographs, what do the lungs look like in a patient with RDS?
like they have a ground glass appearance
How can we measure the level of surfactant in the fetus’ alveolar lining?
because the pulmonary secretions are discharged into the amniotic fluid, analysis of amniotic fluid phospholipids provides a good estimate of the level of surfactant in the fetus’ alveolar lining (L/S ratio >2 is mature lungs)
What is the pathogenesis of necrotizing enterocolitis?
it is uncertain but multifactorial
what are most cases of NEC associated with?
prematurity and enteral feeding
A large number of inflammatory mediators have been associated with NEC. What is one in particular? and what does this cause?
platelet activating factor- has been implicated in increasing mucosal permeability by promoting enterocyte apoptosis and compromising intercellular tight junctions
what does breakdown of the mucosal barrier functions permit?
transluminal migration of gut bacteria, leading to a vicious cycle of inflammation, mucosal necrosis, and further bacterial entry, eventually culminating in sepsis and shock
what is the clinical course of a newborn with NEC?
the onset of bloody stools and abdominal distention in a preterm infant with progressive development of circulatory collapse
What is the most common diagnostic sign- occurring in 98% of patients with NEC?
Pneumatosis intestinalis
what does NEC typically involve?
the terminal ileum, the cecum, and the right colon (although any part of the SI or LI may be involved)
What does the involved segment of bowel in the NEC patient look like?
it is distended, friable, and congestion; it could be frankly gangrenous
what may also be seen with NEC?
intestinal perforation with accompanying peritonitis
Microscopically, what does NEC look like?
mucosal or transmural coagulative necrosis, ulceration, bacterial colonization, and submucosal gas bubbles may be seen
