Transfusion Medicine Flashcards by Kyle Gabrick

Who discovered that blood typing determines the outcome of a blood transfusion ?

Karl Landstiener

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What was the first anticoagulant used to store blood ?

Citrate

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What are the criteria for deferral when donor screening for inclusion in the blood bank ?

Travel to a malaria endemic area
IV Drug Use
Confidential Self Exclusion

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What is the risk of getting HIV, HCV, or HBV after serological testing prior to transfusion ?

1 in 100,000

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Describe the process when preparring RBC’s for the blood bank

RBC’s are separated from platelets and plasma.

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What is the volume of one unit of blood ?

250 ml which contains Fe at the concentration of 1g / dL which can be stored in a refrigerator for 42 days

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What is the problem with blood that has been in storage for 42 days ?

up to 25 % of the transfused red cells undergo hemolysis within 24 hours after transfusion

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What kind of antigens are on the surface of the RBC’s ?

Proteins and complex carbs or lipids. The basic structural core of the complex carbs is the O antigen

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What is the enzyme responsible for the formation of the ABO blood antigen system ?

ABO Glycosyltransferase. which is responsible for attaching the 6th sugar to the O antigen. There are variants of this enzyme for the A B and O antigens

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What does the Glycosyl transferase encode for the A allele ?

The encoded enzyme transfers a sugar called GALNAC to the O antigen. Individuals with two A alleles are termed “Blood Group A”

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What does the Glycosyltransferase transfer for the B allele ?

For the B allele the enzyme transfers GAL (Galactose)

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What does the glycosyltransferase transfer for the O allele ?

Nothing the enzyme is inactive.

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What determines Blood Group in humans ?

Which alleles of the ABO gene (ABO Glycosyltransferase) they inherited.

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If you have type A blood, what type of antibodies are circulating in your blood ( In regard to ABO ) ?

IgM antibodies to the B antigen

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What is Antigenecity ?

A measure of how likely it is that a potential antibody binding site will actually induce an antibody response. This can be a hemolytic response or non-hemolytic response

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Is there allelic variation in the RBC surface proteins ?

Yes a very high level and these will induce antigenecity in the protein. The most antigenic protein on the surface of the RBC is RH-D

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What is Rh-D

A major antigenic site on the RBC that has multiple variant alleles in the human gene pool. The most common one is a complete deletion of the coding sequence.

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What is the concern with the Rh antigen in pregnancy with a D- mother ?

She can develop the D antibody which is able to cross the placenta on future pregnancies. It will kill any baby who is Rh+ or D+ in the future. HEMOLYTIC DISEASE OF THE NEWBORN

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How can you treat hemolytic disease of the newborn ?

By administering Anti-Rh gama globulin

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What happens if your D- patient is sensitized with D+ blood ?

They will develop Anti-Rh antibody. This is not a huge concern in older women and males. But young girls who want to have a child this should always be avoided.

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What percent of D- individuals develop the D antibody when transfused with D+ blood ?

80%

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What is the “Minor Red Cell antigen” ?

Due to allelic diversity there are 20 proteins or glycoproteins that are clinically significant targets due to their allelic diversity ( RhCE ) is one of them

**Blood banks need to routinely screen for these antigens and make sure to provide the patient with blood that has not been sensitized to the antigen.

When sending a blood specimen off to the lab what does a “Type and Screen” mean ?

Typing is for a ABO and Rh antigens

Screening is for recipient antibodies to any known red cell antigen s

What is a “Cross Match” ?

It is performed when you mix the donor red cells and the recipient plasma before transfusing the blood to check for agglutination

What does a negative cross match mean ?

It means that there is a 99% chance there will not be aggregation when the transfusion is given. **If you dont have time to get a cross match and it is an emergency you can get O- which is the universal donor.

Your patient is going to surgery when would you want to send a sample of the patients blood to the bank for testing ? How much blood do you usually want in the room in case of an emergency ?

You will send the blood off to labs before the operation begins because it usually takes the bank a few hours to test the sample for antigen You usually want 2 units of blood in the room incase of an emergency

What is the goal of the RBC transfusion ?

To increase the patients oxygen carrying capacity?

What are the 4 clinical indications for a RBC transfusion ?

1. When the patient is symptomatic 2. Acute Blood Loss or rapid volume expansion 3. During immediately after an acute MI 4. A clear Hgb tread line that you can't yet reverse.

What are 4 mythical indications in which you do NOT need to give your patient a transfusion ?

1. The patient is old and frail. There is no increased survival for patients in their 80's post Op for a hip replacement. 2. Asymptomatic coronary artery disease 3. Expand the blood volume 4. Promote wound healing

For acute blood loss what are the expected time frames that you can expect when ordering blood ?

You can get O- blood immediately Type specific blood takes 20 min extra Typed, screened, and crossmatched takes another 20 min.

Is Anemia a diagnosis ?

NO (Just like how sepsis is a positive blood cult- NOTTT )

At what Hgb level will you need to get a transfusion ?

There is no magic number but the range is generally between 7 and 9.

What is the average patients blood volume ?

5 L

What is the volume of 2 units of PRBC ?

500cc or 10% of blood volume

What are some of the risks associated with RBC transfusions ?

~ 10% risk of an adverse event 1. Seroconversion 2. Circulatory overload 3. TRALI (Usually plasma transfusion )

How do hemolytic reactions generally present ?

Fever- 47.5 % Fever and Chills- 40% Chest Pain- 15 %

As a magician how do you evaluate a transfusion reaction ?

Always assume it could be an acute hemolytic reaction * *Stop the transfusion * *Send the unit back to the blood bank * *Send a fresh specimen along with it

How will the blood bank respond to a transfusion reaction ?

1. Clerical check, did they send the correct unit 2. Look at the serum, tell you if its pink (Hemolysis) or yellow ( icteric; suggests subacute / chronic hemolysis) 3. Recheck ABO type of patient and donor

How will the blood bank work up a transfusion reaction ?

1. Repeat the cross match 2. Repeat the Ab screen 3. Perform the DAT

What is the most common cause of immediate hemolytic reaction ?

Clerical Error

What is the time frame for a delayed hemolytic reaction ?

Hours to days after the transfusion

What are the common causes of delayed hemolytic reactions ?

Minor red cell antigens

What are the common allergic reactions to the plasma components of the blood ? How can these be prevented ?

Uticaria and Anaphylaxis **Premedication with histamine can prevent these reactions

What happens when you get an anaphylactic reaction in an IgA deficient patient ?

Anti- IgA antibody- washed RBC's can eliminate this problem

What is an anamnestic response ?

It is the stimulus of detectable hemolytic levels of Ab from an "Amnestic" state in which they are not detectable by the blood bank.

What are common ways to eliminate clerical errors that lead to hemolytic responses in patients ?

Elaborate patient ID methods Perform multiple ID checks Patient ID and Unit ID need to be verified twice by the RN

If the patient has had a recent acute MI what should you keep their Hct level above ?

Above 30

Are the antigens against blood group A or B hot or cold antigens ?

Even though they are active at 37C they are considered cold antigens because their optimal activity is at 4C

What is the Rh antibody ?

Anti-D

Review: What is the only antibody that can cross the placental barrier ?

IgG

What is the H substance ?

The terminal residue that (N-acetyl glucosamine for group A and D Galactose for Group B ) are attached to. It is a basic antigenic glycoprotein or glycolipid with a terminal sugar L-Frucose on the RBC

Does the O antigen transform H substance ?

No, the O gene is amorf

What are the two structural genes of the Rh system ?

RhD and RhCE which code the membrane proteins that contain the D, Cc, Ee antigens.

Of the Rh genes which is the most significant clinically ?

The presence and absence of the D antigen is the most important because it determines the D + or - phenotype **Anti D is responsable for the clinical problems associated with Rh mismatches.