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Hematology > Transfusion Medicine > Flashcards

Transfusion Medicine Flashcards

1
Q

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

A

Karl Landstiener

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2
Q

What was the first anticoagulant used to store blood ?

A

Citrate

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3
Q

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

A
  1. Travel to a malaria endemic area
  2. IV Drug Use
  3. Confidential Self Exclusion
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4
Q

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

A

1 in 100,000

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5
Q

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

A

RBC’s are separated from platelets and plasma.

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6
Q

What is the volume of one unit of blood ?

A

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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7
Q

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

A

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

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8
Q

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

A

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

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9
Q

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

A

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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10
Q

What does the Glycosyl transferase encode for the A allele ?

A

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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11
Q

What does the Glycosyltransferase transfer for the B allele ?

A

For the B allele the enzyme transfers GAL (Galactose)

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12
Q

What does the glycosyltransferase transfer for the O allele ?

A

Nothing the enzyme is inactive.

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13
Q

What determines Blood Group in humans ?

A

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

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14
Q

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

A

IgM antibodies to the B antigen

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15
Q

What is Antigenecity ?

A

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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16
Q

Is there allelic variation in the RBC surface proteins ?

A

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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17
Q

What is Rh-D

A

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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18
Q

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

A

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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19
Q

How can you treat hemolytic disease of the newborn ?

A

By administering Anti-Rh gama globulin

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20
Q

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

A

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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21
Q

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

A

80%

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22
Q

What is the “Minor Red Cell antigen” ?

A

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.

23
Q

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

A

Typing is for a ABO and Rh antigens

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

24
Q

What is a “Cross Match” ?

A

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

25
Q

What does a negative cross match mean ?

A

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.

26
Q

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 ?

A

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

27
Q

What is the goal of the RBC transfusion ?

A

To increase the patients oxygen carrying capacity?

28
Q

What are the 4 clinical indications for a RBC transfusion ?

A
  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.
29
Q

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

A
  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
30
Q

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

A

You can get O- blood immediately

Type specific blood takes 20 min extra

Typed, screened, and crossmatched takes another 20 min.

31
Q

Is Anemia a diagnosis ?

A

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

32
Q

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

A

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

33
Q

What is the average patients blood volume ?

A

5 L

34
Q

What is the volume of 2 units of PRBC ?

A

500cc or 10% of blood volume

35
Q

What are some of the risks associated with RBC transfusions ?

A

~ 10% risk of an adverse event

  1. Seroconversion
  2. Circulatory overload
  3. TRALI (Usually plasma transfusion )
36
Q

How do hemolytic reactions generally present ?

A

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

37
Q

As a magician how do you evaluate a transfusion reaction ?

A

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
38
Q

How will the blood bank respond to a transfusion reaction ?

A
  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
39
Q

How will the blood bank work up a transfusion reaction ?

A
  1. Repeat the cross match
  2. Repeat the Ab screen
  3. Perform the DAT
40
Q

What is the most common cause of immediate hemolytic reaction ?

A

Clerical Error

41
Q

What is the time frame for a delayed hemolytic reaction ?

A

Hours to days after the transfusion

42
Q

What are the common causes of delayed hemolytic reactions ?

A

Minor red cell antigens

43
Q

What are the common allergic reactions to the plasma components of the blood ?

How can these be prevented ?

A

Uticaria and Anaphylaxis

**Premedication with histamine can prevent these reactions

44
Q

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

A

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

45
Q

What is an anamnestic response ?

A

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

46
Q

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

A

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

47
Q

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

A

Above 30

48
Q

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

A

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

49
Q

What is the Rh antibody ?

A

Anti-D

50
Q

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

A

IgG

51
Q

What is the H substance ?

A

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

52
Q

Does the O antigen transform H substance ?

A

No, the O gene is amorf

53
Q

What are the two structural genes of the Rh system ?

A

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

54
Q

Of the Rh genes which is the most significant clinically ?

A

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.

Hematology (12 decks)

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