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Y2 Clinical Pathology > Transfusion Medicine > Flashcards

Transfusion Medicine Flashcards

1
Q

What are the 3 main components of the blood used in transfusion?

A
  1. Red blood cells
  2. Platelets
  3. Plasma
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2
Q

What happens to whole blood before it can be processed to be used in transfusion?

A

Leucodepletion

whole blood is filtered before further processing to remove white cells

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3
Q

What are the 3 transfusion products taken from plasma?

A

Fresh frozen plasma

cryoprecipitate

fractionation

for factor concentrates (FVIII, FIX, prothrombin complex), albumin, immunoglobulin

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4
Q

What is cryoprecipitate?

A

A frozen blood product prepared from blood plasma

fresh frozen plasma is thawed at 1-6 oC and then centrifuged to collect the precipitate

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5
Q

What should be considered before a transfusion is given?

A

Consider alternatives to transfusion to conserve the blood supply and increase patient safety by avoiding clinically non-essential exposure to donor blood

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6
Q

What is the composition of 1 unit of RBC (1 unit transfusion) like?

What is the haemocrit?

How much will it raise Hb by?

A

Most of the plasma is removed to leave “concentrated red cells”

It has a haemocrit of 60%

1 unit transfusion is expected to raise Hb by 10 g/L

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7
Q

What is meant by “haemocrit”?

A

The ratio of the volume of red blood cells to the total volume of blood

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8
Q

What is plasma replaced by in 1 unit of RBC?

How much iron does 1 unit contain?

A

Plasma is replaced by a solution of electrolytes, glycose and adenine to keep the red cells healthy during storage

one unit of packed red blood cells contains 200-250 mg of iron

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9
Q

How should 1 unit of RBC be stored?

What is the volume of the unit?

A

It is stored at 4oC for up to 35 days from collection

the volume of 1 unit is 280 +/- 60 ml

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10
Q

What is the therapeutic dose of 1 unit of RBC?

What is usual transfusion time?

A

Therapeutic dose is 10-20 ml/kg

usual transfusion time is 1.5 - 3 hours

there is a 4 hour limit from removal from cold storage to the end of the transfusion

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11
Q

Why are red blood cells transfused?

What are the 3 most common indications?

A

They are transfused to restore oxygen carrying capacity

common indications include:

  • significant bleeding
  • acute anaemia
  • chronic anaemia
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12
Q

Based on NICE guidance what is involved in the decision to transfuse in bleeding and anaemia?

A

Bleeding:

  • based on the volume of blood loss

anaemia with severe symptoms:

  • until symptoms resolve (but not > 100 g / L)

acute anaemia with mild symptoms:

  • < 70 g/L for patients without cardiovascular disease
  • < 80 g/L for patients with cardiovascular disease

chronic anaemia:

  • individualised transfusion plans
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13
Q

For what types of anaemia should alternatives to transfusions be used?

A

For any treatable causes of anaemia

  • iron deficiency
  • B12 and folate deficiency
  • erythropoietin treatment for patients with renal disease
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14
Q

What are the 2 different types of platelets that are transfused?

A
  • Pooled platelets
  • Apheresis platelets
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15
Q

How are pooled platelets collected?

A

1 unit of platelet is produced from a unit of whole blood

4-6 of these units (from different donors) are pooled together in a single pack

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16
Q

What is the benefit to using pooled platelets?

A

Less allergic reactions because they contain less plasma

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17
Q

How are apheresis platelets collected?

A

Platelets are removed through an apheresis machine that collects platelets and returns all other blood constituents to the donor

the amount of platelets collected with this procedure represents the equivalent of 4-6 units of random donor platelets

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18
Q

What is the benefit to using apheresis platelets?

A

There is less exposure to infective agents as all the platelets are derived from one donor

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19
Q
A
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20
Q

What is the adult therapeutic dose of platelets?

What is the platelet count per dose?

A

a pool of 4-6 donations or a single apheresis donation

platelet count per dose is 3 x 1011

this is expected to raise platelets by 20-60 x 109 / L

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21
Q

How are platelets stored?

What is the volume of the dose and what is the shelf-life?

A

stored at room temperature (22oC) on an agitator

the shelf-life is 5 days from collection

volume is 250-350 ml

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22
Q

What is the usual transfusion time for platelets?

A

30 mins / unit

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23
Q

What is the limiting factor for the shelf life of platelets?

A

the risk of contamination by bacteria from the donor’s arm that grow at the conditions of storage (22oC)

this can be transmitted to the recipient

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24
Q

Why are platelets transfused?

A
  • to treat bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
  • to prevent bleeding in patients with thrombocytopenia or platelet dysfunction
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25
Q

According to NICE guidance, what influences the decision to transfuse in the treatment of bleeding?

A

massive haemmorrhage:

  • maintain platelet count > 50 x 109 / L

critical site bleeding:

  • in the CNS
  • maintain platelet count > 100 x 109 / L

other clinical significant bleeding:

  • maintain platelet count > 30 x 109 /L
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26
Q

According to NICE guidance, when should a transfusion be performed in the prevention of bleeding?

A

bone marrow failure:

  • platelet count < 10 x 109 / L
  • or < 20 x 109 / L if there is an additional risk e.g. sepsis

prophylaxis for surgery:

  • most major surgeries - < 50 x 109 / L
  • CNS or eye surgery - < 100 x 109 / L
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27
Q

What are the 3 main contraindications for blood transfusion?

A
  • immune thrombocytopenic purpura
  • thrombotic thrombocytopenic purpura
  • heparin induced thrombocytopenia and thrombosis
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28
Q

What is contained within fresh frozen plasma (“ 1 unit of FPP” )?

A

FFP contains all clotting factors at physiological levels

the therapeutic dose is 12-15 ml / kg

this is 4-6 units for the average adult

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29
Q

How is fresh frozen plasma stored?

What is the volume of 1 unit?

A

it is stored at -30oC for up to 36 months

the volume of 1 unit is 300ml

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30
Q

What is the usual transfusion time for fresh frozen plasma?

What happens immediately before use?

A

usual transfusion time is 30 mins / unit

it is thawed immediately before use (takes 20-30 mins)

6 hours after thawing, the levels of labile factors V and VIII begin to diminish

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31
Q

When should FPP be transfused?

A

to replace clotting factors in patients with multiple factor deficiencies (acquired coagulopathies)

  • to treat significant bleeding in patients with abnormal clotting results
  • to correct abnormal clotting results prior to invasive procedures
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32
Q

When should FPP NOT be transfused?

A
  • to treat single factor deficiencies
  • to correct abnormal clotting results in patients that are not bleeding
  • to reverse warfarin
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33
Q

What is used in the reversal of warfarin anticoagulation?

A

prothrombin complex concentrate

(factor IX complex)

contains high concentrations of vitamin K - dependent factors II, VIII, IX and X

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34
Q

What is cryoprecipitate and what does it contain?

A

cryoprecipitate is extracted from FFP during the thawing process

it contains fibrinogen, von Willebrand, factor VIII, factor XIII

35
Q

What is the therapeutic dose of cryoprecipitate?

A

10 - 15 ml / kg

this is 6-10 units

36
Q

How should cryoprecipitate be stored?

What is the volume per unit?

A

stored at -30oC

has a shelf life of 3 years as it is frozen

volume per unit - 15ml

37
Q

When is cryoprecipitate used?

A

it is mainly used as a concentrated source of fibrinogen in acquired coagulopathies

i.e. massive haemorrhage, DIC

38
Q

According to NICE, when should cryoprecipitate be used in the treatment and prevention of bleeding?

A

treatment of bleeding:

  • maintain fibrinogen > 1.5 g/L

prevention of bleeding:

  • maintain fibrinogen > 1 g/L
39
Q

What are the 2 categories of complications of transfusion?

A
  1. immunological
  2. non-immunological
40
Q

When will acute and delayed reactions present after transfusion?

A

acute reactions present < 24 hours post transfusion

delayed reactions present > 24 hours post transfusion

41
Q

What are the non-immunological complications of transfusion?

A
  • transfusion transmitted infections e.g. viral / prion / bacterial
  • transfusion associated circulatory overload (TACO)
  • febrile non-haemolytic transfusion reaction (FNHTR)
  • iron overload
42
Q

What are examples of transfusion transmitted infections?

A
  • HIV
  • Hepatitis B / C virus
  • parvovirus 19
  • hepatitis E / A
  • cytomegalovirus
43
Q

How are viral transfusion tested infections prevented?

A

through a donor questionnaire and mandatory testing

e.g. anti-HIV 1 and 2 and HIV NAT (nucleic acid testing)

44
Q

What usually results from prion transfusion transmitted infection?

How can this be prevented?

A

variant Creutzfeldt-Jakob disease (CJD)

prevention:

  • universal leucodepletion
  • import plasma from countries with low incidence of vCJD
  • inactivate prions with methylene blue
45
Q

When may blood components be contaminated by bacteria?

A
  • bacteria from the donor’s skin during collection
  • unrecognised bacteraemia in the donor
  • contamination from the environment
  • the risk increases with storage after donation
46
Q

How many platelets contain detectable bacteria after transfusion?

A

1 in 2,000 platelets contain detectable bacteria 5 days after donation

the majority are skin contaminants and are non-pathogenic

47
Q

What is the onset of severe infection following bacterial contaminated components?

What are the signs and symptoms?

A

onset:

  • severe reactions may occur early in the transfusion, within first 15 mins

signs and symptoms:

  • rigors
  • high fever
  • severe chills
  • hypotension
  • nausea and vomiting
  • dyspnoea
  • circulatory collapse
48
Q

What is involved in the prevention of bacterial infection during transfusion?

A

bacterial screening cultures of all platelets

49
Q

What causes febrile non-haemolytic transfusion reactions (FNHTR)?

A

FNHTR are due to cytokines or other biologically active molecules that accumulate during storage of blood components

50
Q

What is the incidence of febrile non-haemolytic transfusion reactions (FNHTR)?

How can they be resolved?

A

incidence:

  • 10-30% after a platelet transfusion
  • 1-2% after a RBC transfusion

they are unpleasant but not life threatening

it resolves after discontinuation of transfusion

51
Q

What are clinical features of febrile non-haemolytic transfusion reactions (FNHTR)?

A
  • rise of temperature > 1oC from baseline
  • +/- rigors
  • +/- tachycardia
52
Q

What is the onset of transfusion associated circulatory overload (TACO) like?

How can it be prevented?

A

the onset occurs up to 24 hours after a transfusion

it can be prevented by following guidance on volume and rate of transfusion for each component

53
Q

What are the symptoms and signs of transfusion associated circulatory overload (TACO)?

A

symptoms:

  • sudden dyspnoea
  • orthopnoea
  • tachycardia
  • hypertension
  • hypoxemia

signs:

  • raised blood pressure
  • elevated jugular venous pulse
54
Q

What is meant by hypoxemia?

A

an abnormally low level of oxygen in the blood

it can cause tissue hypoxia as the blood is not supplying enough oxygen to the body

55
Q

What are the risk factors for transfusion associated circulatory overload (TACO)?

A
  • elderly patients
  • small children
  • paients with compromised left ventricular function
  • large transfusion volume
  • increased rate of transfusion
56
Q

What are the main immunological complications of transfusion?

A
  • acute haemolytic transfusion reaction due to incompatibility
  • delayed haemolytic reaction
  • post transfusion purpura
  • allergic / anaphylactic reaction
  • transfusion-related acute lung injury (TRALI)
  • transfusion-associated graft-versus-host disease (TA-GvHD)
57
Q

What is acute haemolytic reaction due to?

A

it is due to transfusion of red blood cells to a recipient that has preformed antibodies against antigens that are expressed on the transfused RBC

this is most often ABO incompatibility

58
Q

How can acute kidney injury result from free haemoglobin?

A

tubular deposition of haemoglobin causes oxidative damage to renal cells

this causes acute kidney injury

59
Q

How can elevated free haemoglobin levels influence endothelial cells?

A
  • elevated free Hb leads to nitric oxide depletion
  • this influences endothelial cells and causes vasoconstriction, hypertension and angina
  • it also causes endothelial cells to release a cytokine shower and to express pro-coagulant molecules
60
Q
A
61
Q

What is the result of endothelial cells releasing a cytokine shower?

A

fever, rigors and hypotension

62
Q

What happens if endothelial cells express pro-coagulant molecules?

A

the clotting cascade is activated

this leads to disseminated intravascular coagulation and bleeding

63
Q

Overall, what are the clinical symptoms of increased free haemoglobin?

A
  • vasoconstriction, hypertension, angina
  • fever, rigors, hypotension
  • bleeding
  • acute kidney injury
64
Q

What is the onset of the acute haemolytic reaction due to incompatibility like?

A
  • severe reactions occur early in the transfusion , within the first 15 mins
  • milder reactions occur later on but usually before the end of the transfusion
  • this is fatal in 20-30% of cases
65
Q

What are the signs and symptoms of acute haemolytic reaction due to incompatibility?

A
  • fever and chills
  • back pain
  • infusion pain
  • hypotension / shock
  • haemoglobinuria (may be first sign in anaesthetised patients)
  • increased bleeding (DIC)
  • chest pain
  • sense of “impending death”
66
Q

How can acute haemolytic reaction due to incompatibility be prevented?

A

by screening patients to identify their blood group

67
Q

What is involved in the pre-transfusion testing on patients?

A

this is done to determine ABO or Rh(D) group

the patient’s plasma is screened for antibodies against other clinically significant blood group antigens

the test is either positive or negative

68
Q

What happens if the pre transfusion testing on patients is postive or negative?

A

negative:

  • no further testing

positive:

  • antibody identification
  • involves testing a patient’s plasma against a panel of red cells containing all the clinically significant blood gorups
69
Q

What is meant by compatibility testing and when is it performed?

A

it is only performed for RBC transfusions

it is the final test before transfusion of RBCs

donor red cells of the correct ABO and Rh group and antigen negative for the antibodies detected in the screen are selected from the blood bank

crossmatching is then performed

70
Q

What is meant by crossmatching?

What are the consequences if it is positive and negative?

A

the patient’s plasma is mized with aliquots of donor red cells to see if a reaction (agglutination or haemolysis) takes place

no reaction:

  • RBC units are compatible
  • no risk of acute haemolysis

reaction:

  • RBC units incompatible
  • risk of acute haemolysis
71
Q

What is a delayed haemolytic reaction due to?

A

post-transfusion formation of new immune IgG antibodies against RBC antigens other than ABO

72
Q

What is the onset of delayed haemolytic reaction like?

What is the main test result that shows this?

A

onset is 3-14 days following a transfusion of RBCs

a direct and indirect antiglobulin test will be positive

73
Q

What are the clinical features and laboratory findings of delayed haemolytic reaction?

A

clinical features:

  • fatigue
  • jaundice
  • and / or fever

laboratory findings:

  • drop in Hb
  • increased LDH (lactate dehydrogenase)
  • increased indirect bilirubin
74
Q

What is the role of the direct anti-globulin test?

(Coomb’s test)

A

it detects antibodies that are bound on RBCs

75
Q

What causes allergic reactions after transfusion?

A

they are due to hypersensitivity of recipient to transfused “random” proteins

this is often after transfusion of components that contain plasma

e.g. FFP, cryoprecipitate, platelets

76
Q

What are the clinical features of allergic reactions following transfusion?

A
  • rash, urticaria, pruritus
  • +/- rigors and fever
  • periorbital oedema (around the eyes)
77
Q
A
78
Q

What is the onset of anaphylactic reaction like?

Which patients are more at risk?

A

onset is a severe, life-threatening reaction soon after transfusion starts

patients with IgA deficiency and anti-IgA antibodies are at higher risk

79
Q

What are the signs and symptoms of anaphylactic reaction?

A
  • laryngeal oedema
  • bronchospasm
  • hypotension
  • swelling
80
Q

What causes transfusion related acute lung injury (TRALI)?

A

it is a serious complication of transfusion

it is due to antibodies in the transfused unit against antigens expressed on the recipient’s leucocytes

it almost always complicates transfusion of plasma-rich components (platelets, FFP)

81
Q

What donor antibodies are involved in TRALI?

What happens when they react?

A

anti-HLA and anti-HNA

they react with antigens on the patient’s WBCs

the activated WBCs lodge in pulmonary capillaries

they release substances that cause endothelial damage and capillary leak

82
Q

What are the criteria for diagnosis of TRALI?

What is involved in prevention?

A

acute lung injury:

  • hypoxemia
  • new bilateral chest X-ray infiltrates
  • no evidence of volume overload
  • sudden onset of acute lung injury occurring within 6 hours of transfusion

prevention:

  • plasma used in UK is only from male donors
83
Q

What are the 2 criteria that must be present in a diagnosis of TRALI?

A
  1. presence of acute lung injury as defined by hypoxia, bilateral CXR infiltrates and the absence of circulatory overload
  2. reaction occurs within 6 hours of transfusion
84
Q
A

Y2 Clinical Pathology (76 decks)

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