Quiz 3 Flashcards
Why do we do prenatal type and screens?
- To ID clinically significant Abs in mom (that can cross the placenta)
- To determine mom’s need for RhIG (Rh neg moms)
- To ID a potential ABO HDFN situation
What kind of Abs do we titer in a pregnant woman?
Abs that react at 37C (IgG)
What are the basic steps of an Ab titer?
- Make a serial dilution with the pt plasma
- React plasma with reagent cells containing Ag for corresponding Ab
- Read agglutination reaction from highest dilution to lowest
How often do we titer pregnant women with significant Abs?
Every month until the end of the 2nd trimester and every couple of weeks throughout the 3rd trimester.
What kind of reagent cells do we use for a titer on a pregnant woman?
Homozygous or heterozygous as long as it’s consistent throughout the pregnancy
What is the end-point of an Ab titer?
The highest dilution showing a 1+ reaction
What are critical titer results?
- Anti-D >/= 16
- Anti-K >/= 8
- Any other IgG Ab >/= 16
- A two tube rise in titer (ex. 1:2 - 1:8)
Why does anti-K have a lower critical titer than anti-D?
- K develops sooner in gestational age than D
- K is expressed on nRBCs and mature RBCs, where D is only expressed on mature RBCs
- Anti-K is more efficient at crossing the placenta
- Anemia caused by anti-K can be more severe earlier in gestation with a lower titer
How should you run titers to avoid subjectivity?
In parallel (last month’s sample and present sample), reading from highest titer to lowest titer
What might a physician do once the critical threshold is reached for an Ab titer?
They might begin monitoring the fetal anemia with Doppler US.
What tests are required before an exchange transfusion or intrauterine transfusion?
- Type and screen, Ab ID, and crossmatch
- Do type and screen on baby if you can for an exchange transfusion
What type of blood is used for an exchange or intrauterine transfusion? What are the special requirements?
- O neg
- Freshest available (collected within 7 days)
- CMV neg
- Hbg S neg
- Leuk reduced (for febrile reactions)
- Irradiated (for GVHD)
- Washed (to remove extra volume)
- Ag negative for mom’s Abs
What additional prep needs to be done before an exchange transfusion? Why?
- AB plasma is added to O neg blood
- To replace the entire whole blood volume
What tests are done routinely on cord blood?
Forward type and DAT
What is the purpose of doing cord blood testing?
- To determine of mom needs postpartum RhIG (Rh neg mom and Rh pos baby)
- To determine if baby’s cells are coated with an allo-Ab
What reagent is used for cold blood DAT?
Monoclonal IgG
When is ABO HDFN most likely to occur? Why?
When the mom is type O, because mom will have a higher titer of anti-A and anti-B Abs.
What will the baby’s DAT result be after ABO HDFN occurs?
It could be DAT pos or neg
What is done next if a baby has a positive DAT after ABO HDFN?
1st - ABO IAT testing using cord serum and screening cells
2nd - an elution can be done to see what Ab is coating the baby’s cells
What basic tests need to be done before a neonatal transfusion (non HDFN)?
Forward type and Ab screen on baby’s sample
If mom has an Ab, what extra steps need to be done before a neonatal transfusion (non HDFN)?
The type and screen still need to be done on the baby and an Ab ID and crossmatch can be done with mom’s sample.
If mom has a history of clinically significant Ab that is not showing up, how should blood be chosen for a neonatal transfusion?
The blood should be negative for the antigen corresponding to mom’s Abs.
When should RhIG be given?
- At 28 weeks for Rh neg moms
- In the case of a traumatic event or an invasive procedure
- If the baby is born in breech position
- In the case of vaginal bleeding
- Postpartum if the baby is Rh pos
If a mom screens positive for anti-D, they can not be given RhIG. T or F?
True
Does DTT treatment weaken/destroy real anti-D or RhIG?
The real anti-D
If mom and baby are Rh neg, what test should be done next?
Weak-D testing on baby
How long can RhIG circulate?
Up to 3 months
How can anti-D be differentiated from RhIG?
A titer can be performed
- RhIG rarely titers above 4
- The specimen can be treated by DTT
What is the principle of the fetal maternal bleed screen (aka Rosette test or FMH screen)? Is it quantitative or qualitative?
Anti-D antisera is used to detect strong D antigen positive cells
(with the use of IgG or indicator cells)
What might be the cause of a false positive in a FMH screen test?
Mom could be weak D pos or DAT pos (indicator cells will bind)
What are possible causes of false negatives in FMH screen testing?
- There is less than 10 mL of fetal blood present in the sample
- Baby is weak D pos (doesn’t have strong expression of antigen)
What should be done when a FMH screen is negative?
The mom should be given a single dose of RhIG
What should be done if the FMH screen is positive?
A KB test or flow cytometry to confirm and quantitate the FMH - for RhIG dosage
What is the principle behind KB testing?
Fetal Hgb is resistant to acid treatment (and adult Hgb gets washed out, leaving mom cells a pale color)
What are the controls for KB testing?
Neg - adult male RBCs
Pos - mix of cord cells and male RBCs
What are possible causes of false positives in KB testing?
- Overstaining
- Small B lymphs that look like fetal cells
- Partial staining of adult cells
- Mom makes Hgb F
How are cell counts for the KB test done?
- Two slides are counted and averaged
- You can count 2,000 cells starting at the feathered edge and use the following calculation - # of fetal cells/total (x 5,000 mL)
- Or you can use a Miller disc and use the following calculation - % fetal cells x 50mL
What cells do you count in each square on the Miller disc for a KB test?
You count adult cells in the small square and fetal cells in both (the whole field)
How many mLs of hemorrhage does 1 dose of RhIG cover?
30 mLs
What is a critical result for a fetal screen?
Pos or neg test is critical, because even if the test is negative the mom should receive one dose of postpartum RhIG within 72 hours of giving birth
What is the transfusion trigger for RBCs?
Hgb less than 7 g/mL
What is the transfusion trigger for platelets (w/ no additional implications)?
Less than 10,000 plts
What is the plt transfusion trigger with a risk of bleeding?
Less than 20,000
What is the plt transfusion trigger if the patient is bleeding or going into invasive surgery?
Less than 50,000
What is the plt transfusion trigger for a patient who will be undergoing neurosurgery or has a head bleed (SAH, SDH, ICH, etc.)?
100,000
What is the transfusion trigger for plts if the patient is on an anticoag drug?
Anyone taking anticoags who is bleeding, has a surgery planned, or has a potential of internal bleeding can qualifies for a plt transfusion.
What is the FFP transfusion trigger?
An INR of 1.5 or greater or a prolonged PT/aPTT (usually approx. 1.5 x the upper limit)
Which contains more factor VIII, Cryo or FFP?
Cryo
What is the transfusion trigger for Cryo?
Less than 100 mg/dL of fibrinogen
What product is best to use as an alternative hemophilia and/or VWD treatment?
Cryo
If the patient doesn’t qualify for the products that have been requested, what should be done next?
You can ask for more information and/or consult with the BB supervisor
- A prospective review may be done to evaluate patient needs
What are the expected increases in Hbg and Hct after one RBC unit has been transfused?
Hgb - increase in 1 g/dL
Hct - increase by 3%
How many concentrates of plts are pooled to make 1 apheresis-size unit?
6 concentrates are pooled to make 1 apheresis unit
What is the expected increase after one apheresis sized unit?
Plts should increased by 30,000 - 60,000.
What is the expected increase after one unit of plt concentrate has been given?
Plts should increase by 5,000 to 10,000
When is plt refractoriness indicated?
It is indicated when you don’t see the expected increase after transfusion of plts
What are the types of plt refractoriness?
- Mechanical
a. spleen sequestration - Serological
a. anti-platelet of anti-HLA in recipient
b. TTP or ITP - Consumption
a. DIC
b. sepsis
What are some actions to take that may help eliminate platelet refractoriness?
You could give…
- HPA-1 negative platelets in the cause of a anti-plt Ab
- HLA typed plts
- Or crossmatched platelets
When should a transfusion “bump” be checked?
Approx. 1 hour after transfusion
Once a unit of platelet concentrate is opened for pooling, how long until it expires?
4 hours after it is spiked (kept at room temp)
How many single units of cryo are pooled to make one adult dose?
10 single units
Once a unit of cryo is spiked, how long before it expires?
4 hours
If cryo is pooled before freezing, how long is the expiration after thawing?
6 hours from thawing time
How long do cryo and plasma last for when they’re frozen?
Once year
Once you thaw plasma how long is it good for?
- 24 hours from thawing (as thawed FFP)
- Or 5 days if relabeled as thawed plasma
- Refrigerated after thawing
Why does FFP expire 24 hours after thawing?
Because of the labile coag factors
How long are RBCs good for after the unit has been spiked?
24 hours
When preparing small volumes of RBCs from larger units there are two methods that can be used. What are they, and what are the expirations for the units derived?
- Syringe method - Exp: in 24 hours
- Bag method with tube welder - Exp: At the original expiration date
What effect does washing red cells have on the hct?
It increased the hct
When reconstituting RBCs, what is added? How does this affect the expiration?
Plasma is added (to make whole blood), the expiration changes to 24 hours anytime the system is opened
What is the basic method for irradiation? How does it affect the expiration?
25 grays of gamma radiation to the midline of the product; the expiration changes to 28 days from the date of irradiation or the original exp. date, whichever comes first
What are the minimum requirements to check for when issuing blood?
2 pt IDs, compatibility testing results, and visual inspection of the product
How fast can FFP, plts, and cryo be transfused?
As fast as the patient can tolerate
How fast are RBCs transfused?
250 mL/hr
What is the shape of the standard filter apparatus? What are the rest of the components?
Y-shape
- inline filter for 150-260 microns (microclots)
- pump
- blood warmers can be attached if needed
How long can our DH coolers store blood? What is the temp range?
4 hours at 1-6C
What is the transport temp rage for RBCs and FFP when not in a cooler?
1-10C
takes about 15 min to get over 10C
How should plts be returned to the lab?
Swirling and 20-24C (same for cryo, but no swirl)
How should plasma be returned (it goes out thawed)?
It should be cooling towards 1-10C (cooler than when it went out, because its kept in a separate cooler)
