HDFN Flashcards
perinatal (near birth)
20 weeks to 28 days after birth
neonate (newborn)
day 0 to 4 weeks
infant
4 weeks to 1 year
gravid
pregnant
gravida
number of pregnancies a single patient has had, regardless they result in a birth
para (parity)
number of pregnancies a patient has had that have reach viability
HDFN
destruction of RBC’s of the fetus or neonate by maternal antibodies
2 most common types of HDFN caused by
Rh antibodies and ABO antibodies
as little as ____ of fetal RBC’s are enough to stimulate formation of anti-D
1 mL
what happens to fetus
RBC’s lyse– release Hgb– indirect bili (does not cause a problem because will cross placenta and mother will conjugate)
what happens to neonate
RBC destruction after birth; can’t effectively conjugate bili and can’t excret = jaundice
how much bili is toxic
18-20
bili is brain called
kernicterus: seizures, poor feeding cerebral palsy
unconjugated bili (indirect)
insoluble
conjugated bili
water soluble
prenatal testing
mother type and screen
if screen is positive tech must do panel
if they have anti-D need to determine if true anti-D or had RhoGham
if true anti-D
order antibody titration and antigen typed
antibody titration
twofold serial dilution of maternal plasma
test against RBC’s that are homozygous for specific antigen
express titer as
reciprocal of highest diltuion
KNOW TITER SCORE
yeah
if titer increases during pregnancy
fetus is presumed antigen positive and at risk for HDFN
rhIG is over titer of
4
if titer >8
a second titer needed at 18-20 weeks
if titer >16
fetus will need middle cerebral artery peak systolic velocity (tells how anemic fetus is )
if 16 or less titer
needs to be measured every 2-4 weeks from 2nd trimester on
if consistently less than 16 titer
it is lower risk
rho gham
binds positive fetal cells and removed from circulation
1 dose of rhoghan =
elimnate 30 mL of fetal whole blood
FMH
used to detect small amounts of rh + in maternal circulation
if FMH +
specific quantity of fetal cells must be calculated and determine dosage of RhoGHAM (Kleihauer-Betke) or flow cytometrey
if FMH -
still give 1 dose of rhogham
FMH is determined by
how mant rossettes per field
kleihauer-betke test
count 3000 cells
volume of FMH= number of fetal cells x 5,000mL/ total cells
round down answer and + 1
principle of kleihauer-betke test
adult Hgb is not resistent to acid so washed out
testing for newborns
cord blood
ABO/Rh - forward and DAT
washing is important for cord blood testing to get rid of
wharton’s jelly
if DAT is + for newborn perform
elution and ID antibody
most common form of HDFN
ABO HDFN
small pool of anti-A and anti-B can cross placenta because
IgG
normal culprint of ABO HDFN is
anti- A,B
who makes anti-A,B IgG
group. O
what type of mothers most likely to have ABO imcompatibility
group O
mothers that are imcompatible with fetal RBC’s for BOTH ABO and D are
protected from sensitization to D
why are they protected
incompatible cells are destroyed in maternal circulation before anti-D can be formed
treatment of HDFN
phototherapy, intrauterine transfusion, exchange transfusion
phototherapy
utilizes light box or bili blanket
how does phototherapy work
the light isomerizes unconjugated bili and makes it water soluble so it can be excreted
intrauterine transfusion
inject “pedi-pak” into umbilical vein (adds irradiation)
indications of intrauterine transfusion
middle cerebral artery-peak systolic velocity, cordocentesis, amniocentesis, hydrops fetalis
what is the goal intrauterine transfusion
maintain Hgb >10 for rest of pregnancy
