HDFN Flashcards
Anti-K HDFN
affects Kell positive precursors in the bone marrow, suppresses rather than hemolytic destroys precursors. Lab results low bilirubin and reticulocytopenia
HDN etiologies
hemolytic disease of newborn: infection, RBC membrane defects, hemolysis due to blood group incompatibility
Most efficient antibody in crossing the placenta
IgG1 (IgG3 and IgG4 also efficient) IgG2 cannot cross
Important considerations of fetal antigen
homozygous vs. heterozygous, degree of antigen expression, could affect the severity
Erythroblastosis fetalis
Anemia, depends on the ability of the fetus to increase hematopoiesis- this causes hepatosplenomegaly. causes portal hypertension and leads to hydrops fetalis
What occurs in system during hydrops fetalis
portal hypertension, edema, effusions, cardiac failure (minimum excess bilirubin-hyperbilirubinemia is not the issue)
Steps of hemoglobin breakdown in fetal/maternal situation
hemoglobin can take one of two routes: it always goes to unconjugated bilirubin, which can then go to the placenta, then to the mothers liver, is broken down to conjugated and excreted by the mother. The unconjugated bilirubin can alternatively go to the immature fetal liver which can’t break it down and it is continued as toxic unconjugated bilirubin- leads to hyperbilirubinemia, jaundice and kernicterus
kernicturus
nuclear jaundice- bilirubin deposits basal ganglia which interferes with mitochondrial function. Bilirubin builds up in babies brain
Quantity of billirubin in kernicturus
> 25mg/dl normal 8-12 mg/dl VLBW (very low birth weight)
outcome of kernicterus
high morbidity and mortality
How much blood is needed to cause immunization
0.1 mL of fetal blood
outcome of RHHDN
historically very severe anemia and death in utero- through use of RHIG significantly reduced
How does ABO incompatility offer protection against alloimmunization
16% vs. 1.5-2%
ABO HDFN hemolysis
usually mild, requiring no treatment, only in O mothers due to ABO antibodies being both IgM and IgG
Prenatal testing performed
ABORH Ab screen, weak D not required. Antibodies ignore: I, P1, Lea, Leb. Testing father for “offending” antigen
Father testing in prenatal studies
Test for antigen, if it’s heterozygous 50/50 chance child received it homo 100% chance child got it. Consider DNA testing if anti-D in mother
Genotyping fetus methods of collection
Amniocentesis, p.b. of mom, CVS (chorionic villus sampling), Cordocentesis
CVS
chorionic villus sampling, collecting from placenta where attached to uterine wall
Cordocentesis
PUBS- percutaneous umbilical blood sampling, use ultrasound to find appopriate placement
Syndromes affecting pregnant women involving blood transfusion
ITP (idiopathic thrombocytopenia) HDFN, FNAIT (fetal and neonatal alloimmune thrombocytopenia)
Earliest HDFN can occur
18-20 weeks
Half life if IgG
21-25 days
Titer considered significant in prenatal testin
> /= 16 or 32. exception is anti-K significant >/=8. There is no need to titer ABO or IgM antibodies
How do you test samples that have been frozen for titers
in duplicate
Doppler ultrasound
non invasive monitoring, measures the blood flow of MCA, increase blood flow indicated anemia- transfusion should be considered, assess hydrops fetalis
MCA
middle cerebral artery
Delta OD
change in the optical density, bilirubin present in the amniotic fluid makes it yellow and changes the optical density. Run the sample to determine OD, a linear downward line charted- compare the result read at 450 with the graph line and document the change, this is the change in the optical density
Reading the results of optical density
0.26-0.46 low risk (zone 1) 0.47-0.90 middle risk (zone 2) 0.91-1.0 High risk (zone 3)
IUT
intrauterine transfusion blood selection: irradiated hgbS negative, CMV- reduced risk, “fresh blood” antigen negative (consider using mom) compatible with mom’s plasma
Facts about IUT
hct decline 1% per day, usually required within 1-2 weeks, holds of hematopoiesis therefore holding of erythroblastosis fetalis, maintain until delivery
Other alternatives to IUT
mother plasma exchange-reduces anibody temporarily, IVIG
infant testing at birth
aborh (no reverse), perform weak D testing be aware of “Blocked D” phenomenon
DAT infant testing
may be positive with RHIG, may be negative with ABO HDN, if DAT+ and mom’s ab screen is negative, consider low incidence antigen.
Good source for antigen negative blood for baby for IUT
mother’s blood