RhIg Flashcards
why do most cases of HDFN due to anti-D occur in Caucasian females?
12-18% Caucasian females are D negative
most common cause of fetal-maternal hemorrhage
delivery
what percent of Rh negative people seem incapable of producing anti-D regardless of how many exposures to the D antigen?
~30%
causes of fetal-maternal hemorrhage
delivery amniocentesis spontaneous or induced abortion chorionic villus sampling cordocentesis rupture of ectopic pregnancy blunt trauma to abdomen
what pregnancy is affected by fetal-maternal bleed?
second and subsequent
high-titer IgG D antibodies of human origin commercially prepared for injection IM or IV
Rh Immune Globulin
incidence of anti-D when RhIg is given at 28 weeks antepartum and postpartum
0.1%
who is a candidate for RhIg?
pregnant Rh negative women with no detectable immune anti-D
Rh negative women with no detectable immune anti-D who have delivered an Rh positive or weak D positive newborn
Rh negative female who receives platelets or red cells from Rh positive donor
RhIg dose calculation if given Rh positive blood products
vials needed = vol of bleed x Hct / 15
RhIg non-candidates
Rh positive
Rh negative women who deliver Rh negative babies
Rh negative women known to have made anti-D (active/immune)
anti-D from RhIg may be detected in antibody screen for how long after injection?
up to 6 months
expected titer of anti-D due to RhIg
<16
does RhIg cross placenta?
yes but no risk to hemolyze
can RhIg cause positive DAY at birth?
yes
when is RhIg administered?
after any invasive procedure
28 weeks
postpartum within 72 hours after delivery
amount of anti-D in one vial of RhIg
300 ug
1 vial of RhIg covers what volume of fetal bleed?
30 mL whole blood
15 mL packed cells
screening test for fetal-maternal hemorrhage
Rosette test/fetal bleed screen
what does Rosette test detect?
Rh positive cells
mechanism of fetal bleed screen
D+ indicator cells form rosettes around D+ fetal cells
is fetal bleed screen qualitative or quantitative?
qualitative
steps of rosette test
incubating mother’s red cell suspension with reagent anti-D
washing
D positive indicator cells added
examined microscopically for rosettes of indicator cells surrounding antibody-coated Rh positive cells
confirmation test for fetal-maternal hemorrhage
Kleihauer-Betke
when is KB test performed?
fetal bleed screen is positive
what does KB test detect?
fetal cells
is KB test qualitative or quantitative?
quantitative
what do fetal cells look like in KB test?
bright pink
what do maternal cells look like in KB test?
“ghost” cells
how many cells are counted in KB test?
2000
what test is used to determine fetal-maternal hemorrhage is mother is weak D positive?
KB
RhIg dose calculation (fetal bleed)
% fetal cells x 50 / 30
mL fetal hemorrhage calculation
KB percent x 50
what safety margin is recommended for fetal maternal hemorrhage when giving RhIg?
add 1 to calculated number of vials
when is mini or micro dose of RhIg given?
before 13 weeks gestation after miscarriages or abortions
how is flow cytometry used in fetal-maternal hemorrhage?
uses reagent containing monoclonal antibody to hemoglobin F
requirement of AABB standards in regards to fetal-maternal hemorrhage
a test to detect FMN is excess of 30 mL be employed to determine if multiple doses of RhIg should be admininstered
