13_Peds II Flashcards
define: sudden infant death syndrome (SIDS)
- sudden death of infant under 1 years old; usually dying while asleep
- remains unexplained after investigation incl
- complete autopsy
- examination of death scene
- review of clinical hx
sudden infant death syndrome:
epidemiology
- A leading cause of death in US infants ages 1 mo- 1 year
- 90% of cases are <6 months (most 2-4 months)
- 3rd cause of death overall in this age group (after congenital anomalies, disease of prematurity and low birth weight)
sudden infant death syndrome:
pathogenesis (“triple risk” model)
- multifactorial condition; triple risk model:
- vulnerable infant: delayed development of arousal and cardiorespiratory control; ? genetic factors
- critical developmental period in homeostatic control (1 mo- 1 year)
-
one or more exogenous stressors:
- prone (face-down) sleeping
- sleeping on soft surfaces
- thermal stress
how does the prone position cause Sudden Infant Death Syndrome?
- increases infant’s vulnerability to noxious stimuli during sleep
- assoc w/ decreased arousal responsiveness compared to supine
what campaign decreased SIDS incidence?
- Recommendation is to have healthy infants on their back;
- “back to sleep” campaign –> substantial decrease in SIDS-related deaths since 1994
- (studies from europe, australia, new zealand, and US
gross morphology of Sudden Infant Death Syndrome?
-
multiple petechiae:
- most common finding in typical SIDS autopsy (80%)
- usually present on thymus, visceral and parietal pleura, and epicardium
- congested lungs
microscopic morphology of Sudden Infant Death Syndrome?
- inconsistent histologic findings, but:
- vascular engorgement w/ or w/out pulmonary edema
- sophisticated morphometric studies: hypoplasia of arcuate nucleus;
- or subtle decrease in brain stem neuronal populations
factors associated w/ SIDS?
some are related to environment (prone sleeping position, soft surface, hyperthermia, co-sleeping with parents);
some related to birth order
what is: accumulation of edema fluid in the fetus during intrauterine growth?
fetal hydrops
what are causes of fetal hydrops?
(2 major types)
- immune hydrops: hemolytic anemia caused by Rh blood group incompatibility b/w mother and fetus
- nonimmune hydrops: due to successful pregnancy prophylaxis
how does severity of fetal hydrops vary?
- RANGE OF INTRAUTERINE FLUID ACCUMULATION
-
Usually lethal:
- progressive, generalized edema of the fetus (hydrops fetalis)
-
Compatible with life:
- more localized and less marked edema, (isolated pleural & peritoneal effusions or postnuchal fluid collections (cystic hygroma)
what type of immune hydrops results from antibody-induced hemolytic disease in the newborn caused by blood group incompatibilty b/w mother and fetus (ABO & Rh)?
Immune hydrops
- Immune hemolysis
- progressive anemia
- tissue ischemia
- intrauterine cardiac failure
- peripheral pooling of fluid edema
what is most common cause of immune hydrops (immune hemolytic disease of newborn)?
- fetomaternal ABO incompatibility currently is the most common cause of immune hemolytic disease (no effective method of ABO incompatibility prevention, but milder than Rh)
- DUE TO REMARKABLE SUCCESS IN PREVENTION OF Rh hemolysis
- Tx is Rh-negative mothers are given anti-D globulin soon after delivery of Rh-positive baby
causes of Nonimmune hydrops?
- cardiovascular defects (structural and functional)
- chromosomal anomalies (45,X karyotype/Turner syndrome, Trisomy 21, Trisomy 18)
- fetal anemia
how does fetal anemia cause nonimmune hydrops?
- homozygous alpha-thalassemia
- causes
- tissue ischemia
- secondary myocardial dysfunction
- circulatory failure
- secondary liver failure
- hypoalbuminemia
- reduced plasma osmotic pressure
- edema
gross morphology of hydrops fetalis?
- generalized accumulation of fluid in fetus
- fluid accumulation particularly prominent in soft tissues of the neck; (cystic hygroma)
which virus is thought to be associated w/ fetal hydrops?
transplancental infxn by parvovirus B19 –> increasingly recognized as important cause
- virus gains entry into erythroid precursors (normoblasts) –> replicates
- cellular injury –> death of normoblasts –> aplastic anemia
HISTO: parvoviral intranuclear inclusions can be seen w/in circulating and marrow erythroid precurosrs (arrows)
what is / cause of erythroblastosis fetalis?
- large number of normoblasts and erythroblasts in peripheral circulation
- caused by increased hematopoeitic activity
define: extramedullary hematopoiesis
- hematopoiesis occurring outside of the medulla of the bone (bone marrow); physiologic or pathologic
- occurs in any solid organ: liver, spleen, kidneys, lungs, lymph nodes, heart
In bone marrow, there is compensatory hyperplasia of erythroid precursors
kernicterus:
pathophysiology
- hemolysis in Rh or ABO incompatibility –> increased circulating bilirubin from RBC breakdown –>
- circulating unconjucated bilirubin is taken up by brain tissue –> toxic effect
- basal ganglia and brain stem are prone to deposition of bilirubin pigement –> characteristic yellow hue to parenchyma
at what point of kernicterus may the CNS be damaged?
when hyperbilirubinemia is markedly elevated
(above 20 mg/dL in full-term infants, lower threshold in premature infants)