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Terms in this set (53)
List 2 conditions that must be met for HDFN to occur.
mother must have an IgG antibody in sufficient quantity to cross the placenta and cause red cell destruction; infant must have the corresponding antigen inherited from the father.
What is the most serious PRENATAL problem associated with HDFN?
Why is bilirubinemia not a problem until after birth?
During pregnancy, the waste byproducts including bilirubin, are passed across the placenta and the mother gets rid of it. After birth, baby's liver is not usually mature enough to handle the bilirubin.
Why is anemia such a problem?
If there are not enough red cells the baby will try to compensate which can lead to heart failure and death.
Why is bilirubinemia such a problem?
If the bilirubin gets too high it deposits into baby's brain causing kernicterus leading to damage ranging from deafness, to mental retardation, to death.
Define erythroblastosis fetalis.
nucleated RBCs in peripherial circulation
Define icterus gravis.
rapid increase in unconjugated bilirubin in the brain resulting in brain damage
Define hydrops fetalis.
generalized edema caused by cardiovascular failure, tissue hypoxia, and death in utero
What are the most common antibodies involved in HDFN?
ABO. They are pre-existing and can occur with the first pregnancy.
Why is anti-D HDFN more severe than ABO HDFN?
The D antigen is fully developed before birth, but ABO are not.
What is the worse case scenario for ABO HDFN and why?
O mom w/A or B baby. Mom has anti-A,B which is usually IgG. The anti-A and anti-B found in A and B moms are usually IgM with a small portion of IgG. Usually the group A baby is worse than the group B because there are so many more A antigens than B antigens.
Does ABO or Rh HDFN have more spherocytes?
ABO. The cells are almost all completely destroyed with anti-D.
What is the DAT for ABO?
weak to negative
What is the DAT for anti-D HDFN?
The mother is B neg and has a negative antibody screen. The baby is B pos and has a positive DAT. What kind of HDFN are we talking about and how would you prove it?
The mother has an antibody to a low-incidence antigen which the baby inherited from the father. Test the mother's serum (if ABO compatible with the father) and the baby's eluate (should have antibody) against father cells and the reaction should be positive.
Mom is B positive with positive antibody screen and baby is O negative with a positive DAT? What antibody could be coating the baby cells?
Infant is O so it is not an ABO antibody; mom is D positive so it is not anti-D; Most common HDFN antibodies other than ABO/D are anti-K and anti-c but it could be any of the other IgG antibodies. It cannot be either anti-Lea or Leb since babies are Le(a-b-).
What tests are done on a mom for her first prenatal workup?
ABO/D typing, antibody screen and titer, if an IgG antibody is identified.
When is a titer considered insignificant?
A titer for an IgG antibody is always significant in a pregnant woman. However, if it is not rising, it means the baby is probably negative for the antigen so the mother is not being stimulated. If < 16 and stable, is it not generally considered significant. A pregnant woman would be tested periodically to make sure it is not rising. However, with anti-K, the titer < 8.
Why do we run titers in parallel with the previously tested sample?
Different technique (shaking, drop size, etc.) and what one person calls a titer of 2 may be a titer of 4 by someone else. Also, different cells will be used and could give a slightly different result.
What does the Color Doppler Middle Cerebral Artery Peak Systolic Velocity measure and what is it used for?
It measures how fast the fetus' blood is flowing. The faster the flow, the more anemic the fetus is.
What is a cordocentesis?
It is a high risk procedure that can obtain or deliver blood directly from or into the umbilical blood vessel.
For what substance is an amniocentesis testing?
Bilirubin giving a measure of the degree of hemolysis
At what optical density is the bilirubin measured?
The ∆OD (delta OD) is measured at 450 nm.
How is the Liley graph used to measure the bilirubin?
The optical density (OD) is plotted on the Liley graph and measured at 450 nm to determine how much danger the baby is in. The graph has been divided into three zones, unaffected, affected and is used to monitor the infant and life-threatening anemia.
What is an intrauterine transfusion (IUT) used for?
To provide antigen negative cells to baby (no lyse). Provides more oxygen carrying cells which would be increased with the new cells.
What is the difference between an intraperitoneal IUT (intrauterine transfusion) and intravascular IUT?
Intraperitoneal IUT places the red cells directly into the peritoneal cavity of the infant and the cells are taken up by the lymphatic ducts; intravascular IUT puts the cells directly into the umbilical vein (percutaneous umbilical blood transfusion).
What are the two most important determinants in whether to perform an exchange transfusion or not?
The bilirubin level and/or how fast it is rising and the cord hemoglobin which can tell you how anemic the fetus is.
What is the single most important serological test in the diagnosis of HDFN after birth?
Mom is an O pos and has an anti-K. The baby is B pos with a 1+ DAT. The baby's eluate is as follows: A1 cells - 0; B cells - 1+; I cell - 0; II cell - 0; III cell - 0. What antibody(ies) is (are) most likely causing the problem?
anti-B from the mother; if it were due to anti-A,B, the A cells would be positive
If the B cells tested in the baby's eluate are positive, why is anti-B not implicated in the HDFN?
The reaction with the B cells is due to anti-A,B, not anti-B. The anti-A and anti-A,B are both attaching to the A cells causing the stronger A cell reaction.
Mom is an A pos with anti-Jka. Baby is a B pos with a 2+ DAT. The eluate reacts as follows: A1 cells - 2+; B cells - wk+; O cells, I, II, were both 2+, the III cell was negative. What is (are) the most likely antibody (ies)?
Since the baby is a B pos, mom's anti-B could have crossed the placenta and attached to the B cells accounting for the wk+ reaction. The A1 cell and the I and II cells are probably Jka positive and the reactions are probably due to the anti-Jka. The B cells could be heterozygous for Jka (giving a weaker reaction) and the A1, I, and II cells could be homozygous for Jka (giving a stronger reaction).
In theory, how could you prove the anti-B vs anti-Jka on the B cells?
Find Jka negative B cells and react them with the eluate. A positive reaction would be due to the anti-B.
What is the purpose of an exchange transfusion?
Since the greatest danger post-delivery is the increased bilirubin, the exchange transfusion removes whole blood (plasma full of bilirubin and antigen positive red cells coated with antibody) from the baby and replaces it with whole blood (plasma without bilirubin and antigen negative red cells) which reduces the level of the bilirubin. It removes antibody coated antigen positive cells which could continue to be lysed increasing the bilirubin titer until all the cells are lysed. It also provides antigen negative cells which will not be lysed to carry oxygen.
What is the purpose of phototherapy?
The UV light will decompose the bilirubin into a non-toxic substance which can be excreted by the baby.
What are the requirements for a woman to be a candidate for RhIg?
36. She must be D negative, Dw negative and not have developed anti-D. Her infant must be D positive or Dw positive (inherited from the father)
Why is RhIg only used to prevent anti-D HDFN?
RhIg is a 300 μg vial of purified anti-D. It prevents the formation of anti-D only. The other antigens do not cause HDFN often enough to warrant the development of an immune globulin for each of them.
What is the dosage for Rh immune globulin?
1 vial of RhIg will neutralize a 30 ml whole blood bleed in a fetal-maternal hemorrhage (fetus will bleed whole blood) or 15 ml of D positive RBCs (not whole blood; packed cells) transfused to a D negative patient.
Why is an O negative mother with an ABO incompatible D positive infant considered to be at a decreased risk of developing anti-D if she didn't get RhIg as compared to an A negative mother with an O positive infant?
The anti-A, -B, and -AB in the O neg mother can remove the A or B pos cells before they can elicit an immune response to the D antigen. The anti-B in the A neg mother will not be able to remove the O pos cells.
Mom is in the hospital to deliver her second child. She is a B R1r with an anti-E. If Dad is an O R1R1, do we need to worry about HDFN?
No, mom has anti-A and anti-E in her serum. Dad is negative for both the A and the E antigen so the child will also be negative for both antigens (Assuming that is the actual father!)
Mom is an O pos with anti-Fya. The baby is an A pos with a 2+ DAT. The eluate is as follows: A1 cells - 2+; B cells - 1+; O cells (I, II, III) - neg. What antibody(ies) is (are) most likely causing the problem?
anti-A,B and anti-A.
What is the principle of the Rosette test?
If the fetus has bled into the mother, the D positive cells will be in the mother's circulation, therefore in the sample used to test the D negative mother. Anti-D added to the system and will coat the D positive fetal cells. The anti-D is washed off and D positive indicator cells are added to the system; these D positive indicator cells attach to the anti-D on the fetal D positive cells and form a "rosette" around the Rh positive fetal cells which are visible microscopically.
What is the principle of the Kleihauer-Betke test?
Fetal hemoglobin is resistant to acid elution; adult hemoglobin is not. The cells are smeared onto a slide which is placed in an acid bath to denature the adult hemoglobin. The slide is stained and the fetal cells appear as bright pink cells while the adult cells appear as "ghost" cells.
If the Kleihauer-Betke is negative, does this mean the mother is not a candidate for Rh immune globulin?
No, she would still get 1 vial. It could mean that the fetal-maternal bleed was too small to detect. You would take the safe route and give 1 vial.
How many units of RhIg do you need to give to a mother if you count 43 fetal cells on the Kleihauer-Betke test?
108 mL bleed
If a D negative adult received a 200 cc unit of D positive red cells, how many vials of RhIg would this individual need to receive to remove the D positive cells?
What is the normal time limit for administering RhIg?
72 hours; however, if the anti-D has not formed yet, the administration can take place at anytime after the 72 hours.
How many weeks old is the fetus when RhIg is given antenatally (before birth)?
If the mother is an R1R1 and the father is an Ror, what antibodies could the mother make that could affect the fetus?
Mom is R1 = DCe, so she is negative for c and E.
Mom is an O, R1r and Dad is an A R2R2. What antibodies could the mother make with this father that would affect the fetus?
Mom is O, R1r = DCe/dce
Mom is a B R2Ro, Dad is an A R1r, and the baby is an O R1R2 with a positive DAT. Which antibody is probably the cause of the positive DAT?
Mom - B R2Ro = DcE/Dce - Already has anti-A and could make anti-C
What chemical can be used to distinguish between an IgG or IgM anti-D in a recently delivered D negative mother who did received RhIg?
2-ME or DTT will destroy an IgM antibody. Add some to the serum and repeat the test. If it is a primary response IgM antibody, it will be destroyed and the repeat antibody screen will be negative. If it is RhIg, it is IgG and will not be destroyed. The repeat antibody screen would be positive.
If Mom is O negative with a negative antibody screen and the newborn is A positive with a positive DAT, what is the MOST LIKELY antibody on the baby's cells?
THIS SET IS OFTEN IN FOLDERS WITH...
Positive DAT and Immune Destruction
Preparation and Use of Blood and Blood Components
The ABO system
The Rh System
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