Glossary of HDN 2

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What is the cause of HDN?
Maternal antibody to fetal RBCs.
How does fetal blood enter the maternal circulation to cause sensitization to D+ cells?
Placental seperation from the uterus.
What are 3 causes of placental seperation?
1. Transplacental hemorrhage
2. Interventions (amniocentesis or chorionic villus sampling)
3. Abdominal trauma
What are 2 terms for placental abnormality?
Placenta previa
Placenta abruptio
What is placenta previa?
Implanted placenta in lower uterus; obstructs birth canal.
What is placenta abruptio?
Separation of placenta from implantation prior to delivery.
What 5 factors influence the maternal antibody response?
1. Immune respnoder genes
2. Fetal RBC dose
3. Exposure frequency
4. FMH length of time
5. ABO incompatibility
Which is better re: HDN, ABO or Rh incompatibility? Why?
ABO; will cause the incompatible cells to be destroyed before Anti-D has a chance to develop!
So what is the exact pathogenesis of HDN?
1. FMH - fetomaternal hemorrhage causes amternal Ab to form against fetal RBC antigens.
2. IgG Ab in later pregnancies will cross placenta and cause hemolysis of incompat. RBCs.
List the 3 categories of HDN:
1. RH system
2. Other blood group Abs
3. ABO antibodies
Which HDN is most severe?
Which HDN is least severe?
Most: Rh
Least: ABO
what is the most common form of HDN?
What ABO bloodtypes are seen in ABO incompatibility HDN in:
MOM: Group O

Infant: A or B
How often does Rh vs. ABO HDN occur in a firstborn?
Rh: 5% of first births
ABO: 40-50%
What are the 3 manifestations of HDN? Which type are they more frequently seen in?
1. Stillbirth
2. Hydrops
3. Severe Anemia
-Seen in Rh, rare in ABO
How does the DAT test compare between Rh and ABO HDN?
Rh: STRONG pos

ABO: weak pos or neg
What type of RBC morphology is seen in HDN of -Rh type vs. -ABO type?
Rh: Macrocytes and nRBCs

ABO: Spherocytes
What is the therapy for Rh HDN?
Exchange transfusion
-Phototherapy is an adjunct to exchange therapy.
What is the therapy for ABO HDN?
Phototherapy alone.
What is the pathophysiology of HDN?
Increased RBC destruction causes anemia and increased production.
What blood picture results from increased erythropoiesis?
Erythroblastosis fetalis
What 4 complications arise in severe HDN?
-Hydrops fetalis (general edema)
-Severe anemia
-Cardiovascular failure
-Tissue hypoxia
What is the best indicator of the severity of HDN at birth?
-Cord blood hemoglobin

>13 is mild, 8-13 is mod, <8 is severe.
What becomes a big problem for newborns with HDN?
Kernicterus from Hyperbilirubin
Why does hyperbilirubinemia develop in HDN only at birth?
Because Mom's liver conjugates teh bilirubin in utero. At birth, the infant's liver is not developed enough to conjugate.
What parameters are used for evaluating the need for exchange transfusion in HDN?
-Indirect bilirubin levels
-Cord blood hemoglobin
What 3 tests are required on Newborn cord bloods?
1. ABO group
2. Rh type
3. DAT
What should be done if the DAT is positive?
-Eluate to identify the antibody type with a panel and screen.
-Test Mom's ABO/Rh, Ab screen and panel if needed.
What special procedure is done when testing cord blood? why?
Washing cells 6x to remove whartons jelly.
What are the 2 types of Elution method?
1. Lui freeze

2. Acid elution (elukit)
What is each elution type for?
-Lui freeze
Lui - for ABO

Acid - for Rh
What are the 4 objectives of an exchange transfusion?
1. Remove Ab-coated RBCs
2. Remove maternal Ab
3. Remove bilirubin
4. Replace RBCs
What are the requirements of the blood used in exchange transfn?
1. Compatible w/ Mom's serum
2. <7 days old, NO ADSOL.
3. Irradiated
4. CMV negative
5. Hb S negative
What volume of blood is given typically given?
2x the infant's blood volume
When ABO types of Mom/Fetus are incompatible what type of unit is given? why?
Group O cells, either packed or in AB serum.
-Because the Baby has A/B antigens and Mom has Antibodies to them. AB serum has no antibodies.
Why is ABO incompatible HDN less severe?
The H antigens are less developed.
What blood would you transfuse?
Mom: A pos, Anti-M, Anti-E
Baby: A pos, R1R2, M pos
Give A pos, R1r, M pos cells because R1r is the most common type of Rh pos, and M is usually insignificant.
What tests should be included in prenatal studies?
If the prenatal screen is negative what should happen?
Repeat in 20-24 weeks, and at delivery
If the prenatal screen is pos, what should happen?
-Antibody ID
-IgM vs. IgG
-Evaluate development of fetal antigens
If Maternal antibody is identified and fetal antigens are developed what should be done?
-Maternal antibody titer
-Freeze serum sample
-Compare results to later titer.
What is the purpose of amniocentesis?
to determine the severity of HDN
What titer result would lead to suspect HDN?
a two-tube increase in titer between first and later tests.
What is amniocentesis?
Indicator of intrauterine hemolysis and fetal well-being per bilirubin pigment level measured in amniotic fluid.
How is amniocentesis performed?
Remove amniotic fluid, measure with spectrophotometer at 450 nm to calculate optical density.
How is the delta OD of amniotic fluid used to evaluate HDN?
With a Liley graph, plotting OD vs. gestational age in weeks.
What does each zone on a Liley graph mean?
Zone 1: Observe fetus for stress and repeat in 2-4 weeks.
Zone 2: Moderate; may need treatment.
zone 3: Severe; deliver/treat.
When is cordocentesis indicated?
When the liley graph value is in the upper mid zone.
Why do cordocentesis?
To measure the baby's Hb and Hct to assess anemia.
How can you be sure the cordocentesis got baby blood?
Test for I antigen with anti-I; should be neg b/c I is adult.
What are the 2 main indications for giving an intrauterine transfusion? (IUT)
1. Correct fetal anemia

2. 24-26 weeks gestation
What 6 requirements must be met when selecting blood for an IUT?
1. Group O neg
2. 75-80% Hct
3. HbS neg
4. CMV neg (leukoreduced)
5. Irradiated
6. CPD (no adsol)
What 2 methods can be used for IUT? Which is quicker?
1. Intraperitoneal
2. Intravascular (faster resolution of anemia)
What is RHOGAM?
A concentrate of mostly IgG Anti-D from pooled human plasma.
What is the theory re: how Rhogam works?
Suppresses mom's immune response to D+ cells by binding them and activating suppressor T cells.
One full dose of RhIg can counteract how much:
-Whole blood?
-Packed red cells?
WB: 30 mls
PRC: 15 mls
How much is one full dose of RhIg?
300 ug of anti-D
how much is a mini dose?
50 ug; 1/6 of a normal dose.
So how much WB and PRCs does a minidose counteract?
5 mls of WB or 2.5 of PCRs
When a prenatal Ab screen is negative when should a woman get Rhogam?
28-32 weeks gestation
What other indication is there for giving Rhogam prenatally?
Amniocentesis, bleeding, or trauma - starting at 16-18 weeks, give a full dose. Then repeat every 12 weeks.
When is Rhogam indicated postnatally?
When Mom is Rh neg and Baby is Rh Pos
Are moms the only ones to get Rhogam?
No; also given after Rh incompatible transfusions.
How much Rhogam is given if a Rh pos platelet is given to a neg patient?
1 dose per 30 platelet donors.
What is a Rosette test?
A qualitative screen to detect fetal Dpos cells in maternal circulation.
what isthe limitation of the rosette test?
It only tells you bleeding has occured, not how MUCH.
How do you tell how MUCH FMH has occured?
Do a Kleihauer Betke stain
What does the Kleihauer betke method detect?
Hemoglobin F
How do you do a Kleihauer betke?
1. Make smear of Mom's postpartum blood;
2. flood w/ acid to elute maternal RBCs. Hgb F survives.
3. counterstain w/ Safranin
How is a kleihauer betke slide evaluated?
Count stained cells within 2000 adult RBCs

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