Transfusion Medicine

Question 1

Is it possible for packed RBC units to contain white blood cells? Can this be problematic? Explain.

Answer 1

Yeah, it can be problematic for immunocompromised patients cuz the WBCs in the transfusion can attack the patient. Most medical centers filter the packed RBC units to remove WBCs, but irradiation is an additional step that can be taken for transfusion in immunocompromised patients.

Question 2

Name all the antigens of the Rh system (letters of the alphabet). Which one is most immunogenic?

Answer 2

D, C, c, E, and e. D is most immunogenic (Rh+ means that D antigen is present)

Question 3

By what mechanism do alloantibodies against D antigen cause RBC destruction?

Answer 3

anti-D antibodies –> opsonization –> extravascular destruction

Question 4

What is the difference between fresh frozen plasma and cryoprecipitate?

Answer 4

FFP is the shit leftover after platelets are taken out of the platelet-rich plasma and it contains all clotting factors.

Cryoprecipitate is the shit that precipitates out of the FFP when it is cooled to 4C, which includes factor VII, vWF, factor XIII, and fibrinogen

Question 5

What is the pathogenesis of TRALI?

Answer 5

Donor antibodies bind to (aka agglutinate) and activate WBCs in the lung interstitium –> cytokines –> increased vascular permeability –> pulmonary edema

Question 6

What are the thresholds (Hb and Hct levels) for transfusing patients w/ RBCs?

Answer 6

Hb < 7g/dL or Hct < 21%

Question 7

What are the corresponding target platelet counts for each following situation: low risk procedures, higher risk procedures, neurosurgery, bleeding patients?

Answer 7

Low risk procedures: 20k platelets
Higher risk procedures: 50k platelets
Neurosurgery: 100k platelets
Bleeders: 50-100k platelets

Question 8

What are four indications for plasma transfusion?

Answer 8

1. Active bleeding w/ multiple clotting factor deficiencies
2. Warfarin reversal in a bleeding patient when PCC is not available
3. Single factor deficiency where recombinant or concentrates are not available
4. Plasmapheresis (ex. for treatment of TTP)

Question 9

What is a better alternative to plasma transfusion for warfarin reversal in a bleeding patient?

Answer 9

Prothrombin complex concentrates (PCC) - contains factor II, VII, IX, X, and proteins C and S (all the vitamin K-dependent ones!)

Question 10

What are the indications for cryoprecipitate transfusion?

Answer 10

Hypofibrogenemia (<150mg) in a bleeding DIC patient, in obstetrical bleeding, or in a massive transfusion protocol. It can also be used in von Willebrand’s disease patients when recombinant wVF is not available.

Question 11

What is the difference between screening and crossmatching?

Answer 11

Screening is when you test patient plasma for the presence of antibodies against other non-ABO blood cell antigens (like Rh-D, Rh-E, Rh-e, etc.). If these are present, O- blood may not be safe. Crossmatching is when you mix patient plasma with a sample of blood that you set aside for possibly giving the patient to see if there is agglutination or hemolysis.

Question 12

Leukoreduction is done to reduce the risk of ______ transmission.

Answer 12

to reduce risk of CMV transmission. It also reduces the incidence of febrile reactions

Question 13

List the signs/symptoms and labs you’d see in a patient with an acute hemolytic transfusion reaction.

Answer 13

Fever, hypotension, flank pain and renal failure cuz free Hb is nephrotoxic, nausea, vomiting, DIC. Labs would show hemoglobinemia, elevated LDH, direct antiglobulin test would be positive.

Question 14

Two hours after giving packed RBCs to your patient, they develop a fever and chills. What is the pathogenesis of this and what are your next steps?

Answer 14

Febrile (non-hemolytic) transfusion reaction - due to cytokine release from confused donor leukocytes that were in the packed RBC package. Next steps are to discontinue transfusion and support & monitor the patient.

Question 15

In which type of blood product does transfusion-related sepsis occur most often? Why?

Answer 15

Platelet transfusion cuz platelets are stored at room temperature and bacteria like that shit

Question 16

Irradiation of blood products is done to remove _______. What are the indications for giving irradiated blood products?

Answer 16

Removes lymphocytes, done for fetuses/newborns, marrow transplant patients, patients with a hematological malignancy or congenital immunodeficiency

Question 17

True or false: in all situations, type, screen, and crossmatching must be performed before giving blood products.

Answer 17

False, in emergency situations universal blood products (O- RBCs, AB plasma) can be used without testing

Question 18

What is the significance of a patient having anti-K antibodies?

Answer 18

These antibodies are capable of fixing complement –> hemolysis, so transfused RBC will need to be K antigen negative

Question 19

One unit of packed RBCs should increase a patient’s Hct by _____%.

Answer 19

3%

Question 20

Of the various types of blood products, which ones need to be crossmatched (if not an emergency situation)?

Answer 20

RBCs and granulocytes

Question 21

Transfusion of plasma is indicated if a patient has an INR above ____ and has an invasive procedure planned.

Answer 21

2

Question 22

What are the transfusion thresholds (for RBC and platelet transfusion, respectively) for hematology/oncology patients who are afebrile and not bleeding?

Answer 22

Hb/Hct: 8g/dL / 24%

Platelets: <10k

Question 23

Do platelets have HLAs on their surface and can patients that get transfusions develop antibodies against these?

Answer 23

Yeah, yeah

Question 24

IgG antibodies against which specific Rh antigens are able to cross the placenta and cause hemolysis in the fetus? What is the treatment to prevent this?

Answer 24

Anti-D and anti-E antibodies can cross placenta –> hemolysis in the fetus

Rh immune globulin can be given to the mother starting at 28 weeks gestation to prevent her antibody titer from increasing, but it only works for anti-D antibody prevention. It is also given 72 hours after delivery.