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70 Cards in this Set
- Front
- Back
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What is the cause of HDN?
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Maternal antibody to fetal RBCs.
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How does fetal blood enter the maternal circulation to cause sensitization to D+ cells?
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Placental seperation from the uterus.
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What are 3 causes of placental seperation?
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1. Transplacental hemorrhage
2. Interventions (amniocentesis or chorionic villus sampling) 3. Abdominal trauma |
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What are 2 terms for placental abnormality?
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Placenta previa
Placenta abruptio |
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What is placenta previa?
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Implanted placenta in lower uterus; obstructs birth canal.
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What is placenta abruptio?
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Separation of placenta from implantation prior to delivery.
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What 5 factors influence the maternal antibody response?
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1. Immune respnoder genes
2. Fetal RBC dose 3. Exposure frequency 4. FMH length of time 5. ABO incompatibility |
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Which is better re: HDN, ABO or Rh incompatibility? Why?
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ABO; will cause the incompatible cells to be destroyed before Anti-D has a chance to develop!
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So what is the exact pathogenesis of HDN?
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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. |
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List the 3 categories of HDN:
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1. RH system
2. Other blood group Abs 3. ABO antibodies |
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Which HDN is most severe?
Which HDN is least severe? |
Most: Rh
Least: ABO |
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what is the most common form of HDN?
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ABO
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What ABO bloodtypes are seen in ABO incompatibility HDN in:
-MOM -FETUS |
MOM: Group O
Infant: A or B |
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How often does Rh vs. ABO HDN occur in a firstborn?
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Rh: 5% of first births
ABO: 40-50% |
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What are the 3 manifestations of HDN? Which type are they more frequently seen in?
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1. Stillbirth
2. Hydrops 3. Severe Anemia -Seen in Rh, rare in ABO |
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How does the DAT test compare between Rh and ABO HDN?
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Rh: STRONG pos
ABO: weak pos or neg |
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What type of RBC morphology is seen in HDN of -Rh type vs. -ABO type?
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Rh: Macrocytes and nRBCs
ABO: Spherocytes |
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What is the therapy for Rh HDN?
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Exchange transfusion
-Phototherapy is an adjunct to exchange therapy. |
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What is the therapy for ABO HDN?
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Phototherapy alone.
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What is the pathophysiology of HDN?
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Increased RBC destruction causes anemia and increased production.
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What blood picture results from increased erythropoiesis?
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Erythroblastosis fetalis
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What 4 complications arise in severe HDN?
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-Hydrops fetalis (general edema)
-Severe anemia -Cardiovascular failure -Tissue hypoxia |
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What is the best indicator of the severity of HDN at birth?
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-Cord blood hemoglobin
>13 is mild, 8-13 is mod, <8 is severe. |
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What becomes a big problem for newborns with HDN?
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Kernicterus from Hyperbilirubin
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Why does hyperbilirubinemia develop in HDN only at birth?
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Because Mom's liver conjugates teh bilirubin in utero. At birth, the infant's liver is not developed enough to conjugate.
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What parameters are used for evaluating the need for exchange transfusion in HDN?
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-Indirect bilirubin levels
-Cord blood hemoglobin |
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What 3 tests are required on Newborn cord bloods?
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1. ABO group
2. Rh type 3. DAT |
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What should be done if the DAT is positive?
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-Eluate to identify the antibody type with a panel and screen.
-Test Mom's ABO/Rh, Ab screen and panel if needed. |
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What special procedure is done when testing cord blood? why?
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Washing cells 6x to remove whartons jelly.
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What are the 2 types of Elution method?
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1. Lui freeze
2. Acid elution (elukit) |
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What is each elution type for?
-Lui freeze -Acid |
Lui - for ABO
Acid - for Rh |
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What are the 4 objectives of an exchange transfusion?
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1. Remove Ab-coated RBCs
2. Remove maternal Ab 3. Remove bilirubin 4. Replace RBCs |
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What are the requirements of the blood used in exchange transfn?
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1. Compatible w/ Mom's serum
2. <7 days old, NO ADSOL. 3. Irradiated 4. CMV negative 5. Hb S negative |
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What volume of blood is given typically given?
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2x the infant's blood volume
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When ABO types of Mom/Fetus are incompatible what type of unit is given? why?
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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. |
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Why is ABO incompatible HDN less severe?
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The H antigens are less developed.
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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.
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What tests should be included in prenatal studies?
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Gr/t/s
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If the prenatal screen is negative what should happen?
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Repeat in 20-24 weeks, and at delivery
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If the prenatal screen is pos, what should happen?
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-Antibody ID
-IgM vs. IgG -Evaluate development of fetal antigens |
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If Maternal antibody is identified and fetal antigens are developed what should be done?
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-Maternal antibody titer
-Freeze serum sample -Compare results to later titer. |
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What is the purpose of amniocentesis?
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to determine the severity of HDN
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What titer result would lead to suspect HDN?
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a two-tube increase in titer between first and later tests.
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What is amniocentesis?
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Indicator of intrauterine hemolysis and fetal well-being per bilirubin pigment level measured in amniotic fluid.
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How is amniocentesis performed?
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Remove amniotic fluid, measure with spectrophotometer at 450 nm to calculate optical density.
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How is the delta OD of amniotic fluid used to evaluate HDN?
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With a Liley graph, plotting OD vs. gestational age in weeks.
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What does each zone on a Liley graph mean?
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Zone 1: Observe fetus for stress and repeat in 2-4 weeks.
Zone 2: Moderate; may need treatment. zone 3: Severe; deliver/treat. |
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When is cordocentesis indicated?
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When the liley graph value is in the upper mid zone.
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Why do cordocentesis?
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To measure the baby's Hb and Hct to assess anemia.
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How can you be sure the cordocentesis got baby blood?
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Test for I antigen with anti-I; should be neg b/c I is adult.
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What are the 2 main indications for giving an intrauterine transfusion? (IUT)
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1. Correct fetal anemia
2. 24-26 weeks gestation |
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What 6 requirements must be met when selecting blood for an IUT?
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1. Group O neg
2. 75-80% Hct 3. HbS neg 4. CMV neg (leukoreduced) 5. Irradiated 6. CPD (no adsol) |
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What 2 methods can be used for IUT? Which is quicker?
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1. Intraperitoneal
2. Intravascular (faster resolution of anemia) |
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What is RHOGAM?
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A concentrate of mostly IgG Anti-D from pooled human plasma.
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What is the theory re: how Rhogam works?
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Suppresses mom's immune response to D+ cells by binding them and activating suppressor T cells.
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One full dose of RhIg can counteract how much:
-Whole blood? -Packed red cells? |
WB: 30 mls
PRC: 15 mls |
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How much is one full dose of RhIg?
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300 ug of anti-D
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how much is a mini dose?
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50 ug; 1/6 of a normal dose.
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So how much WB and PRCs does a minidose counteract?
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5 mls of WB or 2.5 of PCRs
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When a prenatal Ab screen is negative when should a woman get Rhogam?
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28-32 weeks gestation
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What other indication is there for giving Rhogam prenatally?
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Amniocentesis, bleeding, or trauma - starting at 16-18 weeks, give a full dose. Then repeat every 12 weeks.
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When is Rhogam indicated postnatally?
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When Mom is Rh neg and Baby is Rh Pos
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Are moms the only ones to get Rhogam?
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No; also given after Rh incompatible transfusions.
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How much Rhogam is given if a Rh pos platelet is given to a neg patient?
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1 dose per 30 platelet donors.
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What is a Rosette test?
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A qualitative screen to detect fetal Dpos cells in maternal circulation.
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what isthe limitation of the rosette test?
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It only tells you bleeding has occured, not how MUCH.
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How do you tell how MUCH FMH has occured?
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Do a Kleihauer Betke stain
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What does the Kleihauer betke method detect?
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Hemoglobin F
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How do you do a Kleihauer betke?
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1. Make smear of Mom's postpartum blood;
2. flood w/ acid to elute maternal RBCs. Hgb F survives. 3. counterstain w/ Safranin |
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How is a kleihauer betke slide evaluated?
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Count stained cells within 2000 adult RBCs
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