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Essential Hematology > Chapter 27: Blood transfusion > Flashcards

Chapter 27: Blood transfusion Flashcards

1
Q

How many blood group antigens are there?

A

approximately 400

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2
Q

What are the naturally occurring blood group antibodies?

A

Anti-A and Anti-B which are usually IgM and react optimally at cold temperatures.

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3
Q

What is unique about A antigen?

A

There are two subgroups that react differently. A1 cells react more strongly with anti-A abs.

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4
Q

What are the immune blood group antibodies?

A

They occur after exposure to blood group antigens from other people. They are usually IgG and are considered warm antibodies.

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5
Q

What is the risk of infection from blood transfusion?

A

Donors are screened for disease however viruses esspecially those that are carried for many years asympotmatically (latent) can cause disease after blood transfusions.

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6
Q

How is hepatitis transmission prevented in blood transfusions?

A

Donors with a history of hepatitis are deferred. Although those with a history of jaundice can be accepted if they are negative for HBV and HCV markers.

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7
Q

How is HIV transmission prevented in blood transfusions?

A

Homosexuals, bisexuals, IV drug users, prostitutes, hemophiliacs, and there partners are excluded from donating as are people from large parts of sub saharan africa.

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8
Q

The UK screens for which rare virus in blood transfusions?

A

human T cell leukemia virus (HTLV 1 and 2)

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9
Q

For which individuals must cytomegalovirus be screened for before blood transfusion?

A

The immunosuppressed including

(1) premature babies
(2) organ transplant recipients
(3) pregnant women.

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10
Q

What bacteria may transmitted by platelets?

A

Syphilis (platelets are stored at room temperature.)

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11
Q

What parasite can be found even in refridgerated blood?

A

Malaria

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12
Q

What disease is a significant problem with blood transfusions in latin america?

A

Chagas disease.

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13
Q

Do prions pose a blood transfusion risk?

A

Possibly, the UK excludes blood donation recipients as donors for this reason.

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14
Q

What infections can lyse RBCs?

A

(1) Malaria
(2) Babesia
(3) Bartonella
(4) C. perfringens

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15
Q

What substance is used to keep blood from coagulating?

A

citrate

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16
Q

What is the risk of serious infection from a transfusion?

A

1 in 100,000

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17
Q

How are red cells prepared for transfusion?

A

Stored as packed cells not whole blood.

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18
Q

How long can transfusion blood be stored?

A

42 days. If older than 42 days 25% of the RBCs will lyse after transfusion.

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19
Q

What is added to O blood to make it A blood?

A

GalNac

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20
Q

What is added to O blood to make it B blood?

A

galactose

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21
Q

What is the most antigenic protein on red cell surfaces?

A

RhD

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22
Q

What patients have the highest chance for reaction with minor blood group antigens?

A

Patients that are transfused frequently.

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23
Q

What proportion of RhD- individuals will develop antibodies against RhD?

A

80%

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24
Q

What is a crossmatch?

A

It is a test for preformed antibodies against minor blood group antigens

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25
Q

What lab test is indicative of transfusion success?

A

Hemaglobin. direct test for oxygen carrying capacity.

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26
Q

What are the indications for a blood transfusion?

A

Increased HR, Increased RR, confusion, weakness,

(1) Shock due to acute blood loss or volume expansion.
(2) During or after Myocardial infarction
(3) Hgb trendline that you cannot reverse yet

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27
Q

What are not good reasons to transfuse?

A

(1) patient is old and frail
(2) Asymptomatic CAD
(3) Expanded blood volume
(4) to promote wound healing

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28
Q

What can be done in emergencies involving massive blood loss?

A

Type O RhD- blood can be given. It has a fairly high chance of successful transfusion.

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29
Q

How do hemolytic transfusion reactions present?

A

(1) fever
(2) chills
(3) Chest pain
(4) hypotension
(5) nausea
(6) flushing
(7) dyspnea
(8) Hemoglobinuria

30
Q

What are delayed transfusion reactions?

A

reaction may not manifest for several days after the transfusion.

31
Q

What techniques are used in blood group serology?

A

(1) saline agglutination (good for IgM)
(2) Antiglobulin Coomb’s test (IgG) (detects antibodies bound to RBC surface.)
(3) Indirect antiglobulin Coomb’s test (detects anti RBC abs in the serum)

32
Q

How is Patient (recipient) blood screened for compatibility (cross matching)?

A

(1) ABO and RhD compatibility are tested

2) serum is tested against O blood with a series of antigens (Rh D, C, c, E, e, and K.

33
Q

When can blood be transfused without testing?

A

When the patient has had blood group and antibody screens on two separate occasions both being negative, and they have no blood transfusion in between.

34
Q

What are the two types of hemolytic transfusion reactions?

A

(1) immediate

(2) delayed

35
Q

What causes immediate hemolytic transfusion reactions?

A

Massive intravascular hemolysis caused by IgG or IgM antibodies usually against major blood group antigens.

36
Q

What are the causes of delayed type hemolytic transfusion reactions?

A

Preformed antibodies against RBC antigens that are at levels too low to be detected by screening may lead to reimmunization and a hemolytic crisis may occur a few days later.

37
Q

What are the three phases of a major hemolytic transfusion reaction?

A

(1) Hemolytic shock phase
(2) Oliguric phase
(3) Diuretic phase

38
Q

What are the clinical features of the Hemolytic shock phase of a transfusion reaction?

A

Shortly after or during the transfusion

(1) decrease in blood pressure
(2) Urticaria
(3) Precordial pain
(4) sob
(5) If patient is anesthetized jaundice, hemoglobinuria, and DIC may occur
(6) moderate leukocytosis is usual.

39
Q

What are the clinical features of the oliguric phase of hemolytic transfusion reactions?

A

renal tubular necrosis with acute renal failure.

40
Q

What are the clinical features of the diuretic phase of hemolytic transfusion reactions?

A

Fluid and electrolyte imbalance as a result of acute renal failure.

41
Q

What should be done as soon as a patient develops features suggesting a transfusion reaction?

A

The transfusion should be stopped and samples sent to the lab. (clerical errors are the most common cause of major transfusion reactions)

42
Q

What tests should the lab run in the event of a transfusion reaction?

A

(1) blood group and cross match should be repeated on both the donor and recipient pre and post transfusion.
(2) Direct Coombs on post transfusion blood.
(3) recipient plasma for hemaglobinemia.
(4) Test for DIC
(5) test for bacterial contamination
(6) Test urine for hemoglobinuria
(7) later samples must be taken for mehthemaglobin/free hamglobin, and red cell/white cell antibodies.

43
Q

How is a major hemoytic transfusion reaction managed?

A

They are manged by

(1) treating the shock (saline, plasma, dextran, hydrocortisone, antihistamine)
(2) Compatible transfusions may be required.
(3) Renal dialysis if renal failure is severe enough

44
Q

What can cause transfusion related febrile reactions?

A

Anti-leukocyte antibodies (HLA) in the blood.

45
Q

What are non-hemolytic allergic reactions?

A

Hypersensitivity to donor plasma proteins. They may exhibit urticaria, pyrexia, dyspnea, and in severe cases anaphylactic shock.

46
Q

What is post transfusion circulatory overload?

A

This is too much volume in the vascular system. Management is the same as for cardiac failure. Can be prevented by slow infusion accompanied by diuretics.

47
Q

What can be the consequence of transfusing bacterially contaminated blood?

A

Circulatory collapse

48
Q

How can graft vs host disease occur?

A

By the transfusion of active donor lymphocytes to a host that is immunocompromised. Can be prevented by irradiating blood before transfusion.

49
Q

What is transfusion related acute lung injury?

A

Pulmonary infiltrates with chest symptoms. Results from positive transfer of leukoagglutins in donor plasma. Treatment is supportive.

50
Q

What is post transfusion purpura?

A

Destruction of donor and patient platelets 7-10 days after transfusion. results from anti platelet specific antigen abs in the recipient.

51
Q

What causes post transfusional iron overload?

A

Repeated transfusions in the absence of bleeding can cause iron overload. After about 50 units in adults iron overload can cause damage to the liver, heart, and endocrine glands.

52
Q

How does citrate, phosphate dextrose (CPD) anticoagulate blood?

A

It binds up all the calcium

53
Q

Why should fresh blood be used for hemolytic disease of the newborn and other potassium (K) sensitive conditions?

A

Because while in storage RBCs leak potassium into the plasma.

54
Q

What happens to 2,3-DPG during RBC storage?

A

2,3-DPG levels drop during storage.

55
Q

Why is leukodepletion of transfusion blood done in many countries?

A

(1) It reduces incidences of febrile transfusion reactions
(2) reduces the incidences of HLA alloimmunization
(3) Reduces the transmission of viruses such as CMV, and nvCJD prion.

56
Q

What methods can be used to reduce the chance of circulatory or iron overload with transfusions?

A

(1) Iron chelation
(2) diruretics (circulatory overload protection)
(3) Recombinant erythropoietin therapy ( to reduce the need for transfusion)
(4) Factor VIIa (reduces the need for transfusion in bleeding patients)
(5) slow transfusion (prevents circulatory overload)

57
Q

What are the three methods of autologous blood transfusion?

A

(1) predeposit
(2) Hemodilution
(3) Salvage

58
Q

What is predeposit autologous blood transfusion?

A

Patient donates 2-4 units of blood in the weeks leading up to and elective surgery.

59
Q

What is Hemodilution autologous blood transfusion?

A

Blood is taken from patient just before a surgical procedure and then reinfused at the end of the prodedure.

60
Q

What is salvage autologous blood transfusion?

A

Blood is collected during heavy blood loss and then retransfused into the patient later.

61
Q

What is a potential hazard of autologous transfusion?

A

There is a greater risk of bacterial contamination of the donated blood especially in salvage transfusion.

62
Q

What patients are the best candidates for autologous blood transfusion?

A

Healthy patients with multiple anti blood cell antibodies

63
Q

When are granulocyte concentrates given?

A

Sometimes they are given to patients with severe neutropenia. However, there is a risk of viral transmission and GVHD. It is not usually possible to give enough.

64
Q

For what are platelet concentrates given?

A

Platelets are given to stop bleeding in patients with serious hemorrhage and thrombocytopenia or platelet disorders. Platelets concentrates can also be given prophylactically for platelet disorders to keep platelets above a certain level.

65
Q

For what conditions is platelet transfusion contraindicated?

A

(1) Autoimmune TTP (unless there is massive hemorrhage)
(2) HIT
(3) TTP
(4) hemolytic uremia syndrome

66
Q

For what is freshly frozen plasma used?

A

(1) replacement of coagulation factors
(2) After massive transfusions (liver disease, DIC)
(3) To reduce warfarin after surgery
(4) TTP

67
Q

When is human albumin solution given?

A

It is a plasma expander

(1) fluid replacement in plasmapharesis
(2) fluid replacement in hypoalbuminemia
(3) to alter osmotic effect.

68
Q

When is salt poor human albumin solution used?

A

It is used for severe hypoalbuminemia when it is necessary not give electrolytes. Used in nephrotic syndrome and liver failure.

69
Q

For what is cryoprecipitate used?

A

To replace fibrinogen in DIC, massive transfusion, or liver failure.

70
Q

When is protein C given?

A

In severe sepsis with DIC

71
Q

Blood loss less than what amount does not usually require transfusion in adults?

A

Blood loss less than 500ml usually does not require transfusion.

Essential Hematology (22 decks)

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