Hemolytic Disease of the Newborn- Krafts Flashcards
What is hemolytic disease of the newborn (HDN)?
Hemolysis in a newborn or fetus caused by blood-group incompatibility btwn mother and child
What is hydrops?
Means accumulation of edema fluid in the fetus during intrauterine growth….can occur in many fetal conditions.
What is hydrops fetalis?
When the fluid accumulation is severe and generalized
What is Erythroblastosis fetalis?
It means that early red cell precursors are showing up in the peripheral blood….can happen in any severe anemia.
What is the mechanism of hemolytic disease of the newborn?
- Fetus inherits blood group antigen (usually Rh D antigen) from the father, this is foreign to the mother (meaning that she is Rh (-)
- Fetal blood gets into mom’s circulation during last trimester or at childbirth.
- Mom makes antibodies to these blood group antigens.
- Antibodies (IgG) cross the placenta, attack baby’s RBC’s causing hemolytic anemai (THIS IS ONLY IN THE SECOND PREGNANCY IF SHE HAS ANOTHER Rh + BABY!!!!!)
What are the consequences of Hemolytic Disease of the Newborn?
Extramedullary hematopoiesis
Heart and liver failure
Jaundice
Kernicterus
What is extramedullary hematopoiesis?
Happens in mild anemia, hematopoiesis happens outside the bone marrow….sometimes the liver and spleen can produce enough RBC to maintain normal numbers
How do they get heart and liver failure?
in severe anemia, heart and liver suffer hypoxic injury resulting in circulatory and hepatic failure. Liver failure results in dec. protein levels so oncotic pressure is decreased. Heart failure causes an inc. in venous pressure because blood is backing up behind the heart…..if severe enough these things can lead to generalized edema and ascites….aka hydrops fetalis (this varies in severity)
How does jaundice occur?
Accumulation of unconjugated bilirubin due to hemolysis of RBC’s
What is kernicterus?
Unconjugated bilirubin is water insoluble, this binds to the lipids in the blood brain barrier of a developing fetus causing serious CNS damage. Brain becomes enlarged, edematous, and yellow.
Why is HDN uncommon in the first pregnancy?
Mom makes IgM antibodies during the first pregnancy when exposed to the D antigen…..IgM can’t cross the placenta. But, if she has another baby that is Rh + for the D antigen she will have IgG floating around which can cross the placenta…..BAD NEWS!!!
How do you test for HDN?
Direct antiglobulin test- will be positive in baby (baby’s cells are coated with mom’s antibodies)
Indirect antiglobin test will be positive in mother (could be artificially positive if mom gets Rhogam at 28 wks)
How do you treat HDN?
Give the mother anti-D antibody (Rhogram) at 28 wks and again within 72 hrs of the delivery to Rh negative moms…..this neutralizes the D+ fetal red cells in circulation by coating them in antibody……Mom can’t make any anti-D antibodies to it!!!!
What is the Kleihauer-Betke test? Why would you ever want to do this test?
- Do mom’s blood smear
- Expose blood to acid bath, removing adult Hgb but not fetal Hgn.
- Stain smear: baby cells appear pink, mom’s appear very pale “ghosts”
- Count lots of cells and report percentage that are fetal.
This is to determine dosing for Rhogam!!!!
Explain flow cytometry? What is it good for?
- Use mom’s blood
- apply anti-HbF antibody
- run flow, look for cells staining intensely (these are baby’s cells)
Used to determine dosing for Rhogam…..this test is used more often unless you’re out in the boondocks and don’t have flow cytometry.
