Diseases of Infancy and Childhood: Prematurity, neonatal respiratory distress syndrome, necrotizing enterocolitis

Question 1

what is prematurity defined as?

Answer 1

gestational age less than 37 weeks

Question 2

What are the 4 risk factors for prematurity?

Answer 2

preterm premature rupture of membranes (PPROM), intrauterine infection, uterine/cervix/placental abnormalities, and multiple gestation

Question 3

what is the major cause of preterm labor and what is an example of this?

Answer 3

intrauterine infection- funisitis (infection of the umbilical cord)

Question 4

What are the 4 major hazards associated with prematurity?

Answer 4

RDS, NEC, sepsis, and intraventricular and germinal matrix hemorrhage

Question 5

what is fetal growth restriction and how is this different than preterm infants?

Answer 5

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

Question 6

what are small for gestational age (SGA) infants at risk for?

Answer 6

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

Question 7

what is the most common cause of respiratory distress in the newborn?

Answer 7

neonatal respiratory distress syndrome (RDS)

Question 8

what is another name for respiratory distress syndrome?

Answer 8

hyaline membrane disease

Question 9

who is at risk for having RDS?

Answer 9

premature neonates

Question 10

what is the fundamental defect in RDS?

Answer 10

pulmonary immaturity and deficiency of surfactant

Question 11

what is surfactant produced by?

Answer 11

type II alveolar cells- this becomes accelerated after the 35th week of gestation in the fetus

Question 12

surfactant synthesis is modulated by a variety of hormones and growth factors including what?

Answer 12

cortisol, insulin, prolactin, thyroxine, and TGF-beta

Question 13

what happens with a deficiency of surfactant?

Answer 13

the lungs collapse with each successive breath, so infants must work as hard with each successive breath as they did with the first

Question 14

what is the problem with stiff atelectatic lungs compounded by?

Answer 14

the soft thoracic wall that is pulled in as the diaphragm descends

Question 15

what chain of events follow atelectasis?

Answer 15

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)

Question 16

what is the etiology of RDS?

Answer 16

prematurity

Question 17

what are the associations of RDS?

Answer 17

male gender, maternal diabetes, and cesarean delivery

Question 18

what does control of RDS focus on?

Answer 18

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

Question 19

on radiographs, what do the lungs look like in a patient with RDS?

Answer 19

like they have a ground glass appearance

Question 20

How can we measure the level of surfactant in the fetus’ alveolar lining?

Answer 20

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)

Question 21

What is the pathogenesis of necrotizing enterocolitis?

Answer 21

it is uncertain but multifactorial

Question 22

what are most cases of NEC associated with?

Answer 22

prematurity and enteral feeding

Question 23

A large number of inflammatory mediators have been associated with NEC. What is one in particular? and what does this cause?

Answer 23

platelet activating factor- has been implicated in increasing mucosal permeability by promoting enterocyte apoptosis and compromising intercellular tight junctions

Question 24

what does breakdown of the mucosal barrier functions permit?

Answer 24

transluminal migration of gut bacteria, leading to a vicious cycle of inflammation, mucosal necrosis, and further bacterial entry, eventually culminating in sepsis and shock

Question 25

what is the clinical course of a newborn with NEC?

Answer 25

the onset of bloody stools and abdominal distention in a preterm infant with progressive development of circulatory collapse

Question 26

What is the most common diagnostic sign- occurring in 98% of patients with NEC?

Answer 26

Pneumatosis intestinalis

Question 27

what does NEC typically involve?

Answer 27

the terminal ileum, the cecum, and the right colon (although any part of the SI or LI may be involved)

Question 28

What does the involved segment of bowel in the NEC patient look like?

Answer 28

it is distended, friable, and congestion; it could be frankly gangrenous

Question 29

what may also be seen with NEC?

Answer 29

intestinal perforation with accompanying peritonitis

Question 30

Microscopically, what does NEC look like?

Answer 30

mucosal or transmural coagulative necrosis, ulceration, bacterial colonization, and submucosal gas bubbles may be seen