3.20.14*/4.2.14 Transfusion Medicine I and II

Question 1

what is the effect of giving one unit of blood

Answer 1

250 ml per unit; 1 unit will increase Hgb ~1g/dL

Question 2

Hematocrit

Answer 2

The Hematocrit is the fraction of the blood volume occupied by cells

- Requires two measurements on the hematology analyzer
- Usually but not always equal to 3 x Hgb

Question 3

what is the structure of the O antigen?

Answer 3

spingosine or membrane protein backbone with five consecutive hexameric sugars

Question 4

Structure of type A antigen

Answer 4

ABO glycosyltransferase adds GalNac to O antigen

Question 5

structure of B type blood antigen

Answer 5

ABO glycosyltransferase adds Gal to O antigen

Question 6

acute hemolytic transfusion reaction

Answer 6

when a patient is given ABO-incompatible blood

Question 7

Rh negative

Answer 7

means individual has two deleted Rh alleles and does not express the Rh antigen (15% of white population).

Question 8

what prevents hemolytic disease of the newborn?

Answer 8

anti-Rh-gamma globulin

Question 9

what is a “type and screen” of a recipient blood sample

Answer 9

type: blood typing for ABO and RhD antigens
screen: screen for recipient antibodies to any known/minor red cell antigens

Question 10

crossmatch

Answer 10

mixing donor red cells with patient plasma

Question 11

what hgb increases patient survival after MI

Answer 11

> 10

Question 12

What percentage of blood volume is in 2 units of prbc?

Answer 12

2 units prbc = 500 cc 10% of blood volume (can cause circulatory overload)

Question 13

What patient population is at risk for graft v. host disease?

Answer 13

Graft versus host disease is a higher risk in immunocompromised patients (HIV, chemotherapy, transplant recipients); these patients usually receive irradiated red cell units to prevent donor leukocytes from proliferating in response to host antigens and subsequently damaging host tissues (typically bone marrow, skin, and gut epithelium).

Question 14

Common problems associated with transfusion

Answer 14

CMV seroconversion: ~10%
Fever without hemolysis: ~1%
Development of an anti-rbc antibody: ~1%
Urticaria: ~1%
Circulatory overload: 5% *
Hemolysis, immediate or delayed: 1 in 2500
Infection: < 1 in a 100,000
Graft versus Host disease: 1 in a million*

Question 15

Delayed hemolytic transfusion reaction

Answer 15

similar to acute reaction but can occur up to a week after transfusion. Antibody is below detectable limit but reproduced after transfusion. Usually caused by minor antigens.

Question 16

Febrile reactions

Answer 16

due to white cell antibodies (HLA) sensitization by preganancy or previous transfusion. Can produce rigots, pyrexia and rarely pulmonary infiltrates. Risk minimized with irradiated blood.

Question 17

circulatory overload

Answer 17

too much fluid in system, can lead to cardiac failure. Rare.

Question 18

what alleles determines your ABO blood type

Answer 18

ABO glycosyltransferase

Question 19

Fever:  47.5%
Fever and chills:  40%
Chest pain:  15%
Hypotension:   15%
Nausea:  5%
Flushing:  5%
Dyspnea:  5%
Hemoglobinuria:  2.5%

Answer 19

Acute hemolytic reaction. caused by unmatched type or RhD.

Can lead to renal failure/death

Question 20

delayed hemolytic transfusion reaction

Answer 20

Ab previously developed to minor RBC antigen but was too low to detect prior to transfusion.

Question 21

Allergic reactions to plasma components:

Answer 21

After the first urticarial reaction, premedicate with antihistamines for any subsequent transfusions
If that doesn’t work, request washed red cells for any subsequent transfusions. Some anaphylactic reactions occur in IgA deficient patients with anti-IgA antibody. Can get red cells from IgA deficient donors. Washed red cells might work.

Question 22

Benign febrile reactions

Answer 22

• Common and preventable with acetaminophen
  
  • You must make sure it’s not hemolysis.
    Pretreat with your favorite anti-pyretic
    Leukoreduced red cells will almost always prevent this