Transfusion Medicine

Question 1

Preservatives added to blood when it is donated

Answer 1

CPD-adenine:

Citrate chelates calcium to prevent clotting

Phosphate acts as a buffer to maintain the pH within physiologic range

Dextrose provides a source of food for the red cells during storage

Adenine enhances cell viability

Question 2

Fractionation of blood donations

Answer 2

Question 3

Effects of removing WBCs from blood donations

Answer 3

• Prevents graft vs host disease (this risk can be further reduces by irradiation)
• Prevents MHC reactions (remember, all the other blood cells are not nucleated and so don’t have MHC)
• Reduces risk of CMV infection

Question 4

ABO antigens

Answer 4

Question 5

ABO antigens reside on ___.

Answer 5

ABO antigens reside on band 3.

Question 6

Rh positive and Rh negative refer to the presence or absence of ___.

Answer 6

Rh positive and Rh negative refer to the presence or absence of the Rh D antigen.

Question 7

Important distinction between ABO and Rh D reactions

Answer 7

The ABO reaction is via IgM and involves the fixation of complement, leading to intravascular hemolysis

The Rh D reaction is via IgG and does not involve complement, but rather results in opsonization-mediated phagocytosis, leading to extravascular hemolysis

Question 8

Most cases of autoimmune hemolysis due to warm IgG antibodies are caused by . . .

Answer 8

. . . autoantibodies against the Rh antigens

Question 9

Principal mode of testing for blood antigens

Answer 9

standardized antibody-based agglutination assays, similar to Coomb’s test

Question 10

Sample transfusion blood test result table

Answer 10

Question 11

Indications for transfusion

Answer 11

• Postural hypotension (strongly suggests hypovolemia)
• Anemia due to intracorpuscular hemolysis
  *

Question 12

In patients with renal failure, ___ should be a preferred treatment over transfusion.

Answer 12

In patients with renal failure, EPO supplementation should be a preferred treatment over transfusion.

Question 13

In patients with anemia due to non-genetic production problems, before jumping to transfusion, ___ should be attempted

Answer 13

In patients with anemia due to non-genetic production problems, before jumping to transfusion, addressing the cause of the production problem should be attempted

This goes for: Loss of EPO production, nutritional anemias, anemias secondary to solvable disease processes

Question 14

Evidence-based hemoglobin threshold for transfusion

Answer 14

A hemoglobin level of 7 to 8 g/dL has been found to be appropriate.

Take other factors into consideration, such as carbon monoxide status for smokers

Question 15

Cases where you should be a bit more lenient with transfusions

Answer 15

Patients with anemia who begin to experience angina

Patients with genetic production problems that have shown evidence of poor compensation

Question 16

One ‘unit’ of blood

Answer 16

525 mL

Question 17

The primary indication for platelet transfusion is ____

Answer 17

The primary indication for platelet transfusion is bleeding due either to thrombocytopenia or, much less often, to defective platelet function.

Question 18

Detection of GI blood loss vs platelet count

Answer 18

The takeaway here is that there is little or no benefit toward preventing major hemorrhage in transfusing a patient to more than ~10,000 platelets per microliter.

Question 19

The primary indication for transfusion of fresh frozen plasma is . . .

Answer 19

The primary indication for transfusion of fresh frozen plasma is correction of deficiencies of multiple clotting factors, as may occur in liver disease, overdosing of warfarin, and disseminated intravascular coagulation

Question 20

Infusions of plasma for hemorrhage

Answer 20

Infusion of fresh frozen plasma may be beneficial following acute massive hemorrhage because it restores both lost colloid (principally albumin), which helps to expand intravascular volume, and clotting factors.

Question 21

Cryoprecipitate

Answer 21

The protein precipitate from plasma that forms at 4^oC

Contains factor VIII, von Willebrand factor, factor XIII, and fibrinogen

Currently, cryoprecipitate is primarily used for treatment of hypofibrinogenemia.

Question 22

Immediate hemolytic reactions are nearly always due to ___

Answer 22

Immediate hemolytic reactions are nearly always due to ABO incompatibility

Question 23

Symptoms of acute transfusion rejection

Answer 23

• Fever
• Chills
• Dyspnea
• Tachycardia
• Hemoglobinuria
• Severe pain, usually in lower back
• For large transfusions, hypotensive shock, oliguria, and disseminated intravascular coagulation may be precipitated

Question 24

Many of the symptoms of acute transfusion rejection are likely to be missed ____

Answer 24

Many of the symptoms of acute transfusion rejection are likely to be missed if the patient is under general anesthesia

With the exception of hypotension

Question 25

At the first signal that incompatible blood may have been administered, . . .

Answer 25

. . . the infusion must be stopped, the identity of the patient and unit must be reconfirmed, and serologic testing repeated on the donor and recipient blood.

Question 26

Acute vs delayed transfusion rxn

Answer 26

Question 27

Patients develop alloantibodies to protein antigens in foreign blood only . . .

Answer 27

Patients develop alloantibodies to protein antigens in foreign blood only after pregnancy or transfusions.

Question 28

Treating delayed transfusion reactions

Answer 28

Delayed hemolytic transfusion reactions usually do not require therapy.

Rather, just take extra steps to ensure that the next transfusion is a better match.

Question 29

Timecourse of delayed transfusion reaction

Answer 29

Question 30

Hemolytic disease of the fetus and newborn

Answer 30

Involves an immunologic response following the “transfusion” of red cells from the fetus into the maternal circulation. Maternal Rh D alloimmunization is by far most common. Similar to delayed transfusion reaction.

Question 31

Scenario for most cases of HDFN

Answer 31

• Father Rh+
• Mother Rh-
• Child inherits Rh+ from dad
• Mother becomes immunized but first pregnancy otherwise asymptomatic
• Next child also inherits Rh+ from dad
• This time the mother produces more antibody, which crosses into fetal circulation via FcRn
• The fetus develops a severe hemoltyic anemia from mom’s antibodies, with hydrops and generalized tissue hypoxia
• Unconjugated-bilirubin from hemolysis can also cause irreversible brain damage to infant

Question 32

Treating HDFN

Answer 32

If suspected in third trimester, an intrauterine transfusion may be performed to alleviate symptoms.

Question 33

Preventing HDFN

Answer 33

HDFN is rarely encountered today thanks to the discovery 50 years ago that the administration of anti-D immunoglobulin (RhoGAM) to Rh-negative mothers after their first delivery safely and effectively suppresses sensitization to Rh D and prevents the development of HDFN in subsequent pregnancies.

Question 34

Transfusion-related lung injury

Answer 34

Acute interstitial pneumonitis that appears within 6 hours of transfusion, accompanied by dyspnea, tachycardia, hypoxemia, fever, and hypotension.

Thought to be due to donor antibodies binding and activating host neutrophils or pulmonary endothelial cells.

Most common cause of transfusion-related death

Question 35

Treating TRALI

Answer 35

Primarily supportive

• Oxygen
• Mechanical ventilation
• Resolution in 48-96 hours
  *

Question 36

Preventing TRALI

Answer 36

Use of male serum reduces risk, as anti-HLA antibodies are thought to mediate many cases, and women who have been pregnant are more likely to be sensitized against HLA.

Cases of suspected TRALI are investigated by the blood bank. Donors of blood products believed to have caused TRALI are permanently banned from donating blood.

Question 37

Infectious risks from transfusion

Answer 37

Question 38

Transfusion risk summary

Answer 38

Question 39

ABO antigens are ___ while Rh antigens are ___.

Answer 39

ABO antigens are carbohydrate while Rh antigens are protein

Question 40

“Crossmatch” test

Answer 40

Donor’s erythrocytes

Patient’s plasma

Look for agglutination