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
- 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
- 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
- What are the 3 manifestations of HDN? Which type are they more frequently seen in?
- 1. Stillbirth
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
- 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)
- 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
- 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 - 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.
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)
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:
-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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