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8. CP - Core Haematology > (36) Blood transfusion > Flashcards

(36) Blood transfusion Flashcards

1
Q

What is leucodepletion?

A

Whole blood is filtered to remove white blood cells

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2
Q

What are the 3 main contents of whole blood after leucodepletion?

A
  • red blood cells
  • platelets
  • plasma
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3
Q

What is cryoprecipitate?

A

Frozen blood product prepared from plasma.

  • fresh frozen plasma is centrifuged and the precipitate collected
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4
Q

How much of the blood does plasma make up?

A

55% of the total blood volume.

  • made up of primarily of water with minerals, salts, ions, nutrients, and proteins - red blood cells, leukocytes, and platelets are suspended within the plasma
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5
Q

Give examples of components of plasma separated out during fractionation

A
  • factor concentrates (FVIII, FIX, prothrombin complex)
  • albumin
  • immunoglobin
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6
Q

What is the usual transfusion time? (1 unit RBC)

A

1.5-3 hours

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7
Q

How is RBC for transfusion stored?

A

At 4 degrees C for up to 35 days from collection

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8
Q

What is the time limit for how long blood can be kept after removal from storage?

A

4 hour limit from removal from cold storage to end of transfusion

Use blood warmer for rapid transfusion

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9
Q

What does a blood transfusion sample consist of?

A

Most of the plasma is usually removed to leave concentrated red cells and replaced by a solution of electrolytes, glycose and adenine to keep red cells healthy during storage

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10
Q

Why do we transfuse patients?

A
  • prevent symptoms of anaemia
  • improve quality of life of anaemic patients
  • prevent ischaemic damage of end organs in anaemic patients
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11
Q

The symptoms of anaemia are due to what?

A

Tissue hypoxia

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12
Q

What is the transfusion threshold (trigger)?

A

The lowest concentration of Hb that is not associated with symptoms of anaemia

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13
Q

Transfusion thresholds differ in various subgroups of patients depending on what?

A

The balance between mechanisms of adaptation to anaemia and O2 requirements

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14
Q

What are the different mechanisms of adaptation to anaemia?

A
  • increased cardiac output
  • increased cardiac artery blood flow
  • increased oxygen extraction
  • increase of red blood cell 2,3-DPG (diphosphoglycerate)
  • increased production of EPO
  • increased erythropoiesis
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15
Q

What can the kidneys do to maintain tissue oxygenation in anaemia?

A

Increased erythropoietin release

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16
Q

What can the bone marrow do to maintain tissue oxygenation in anaemia?

A

Increase erythropoiesis

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17
Q

What can the peripheral organs do to maintain tissue oxygenation in anaemia?

A
  • decrease tissue pH
  • increase O2 extraction
  • vasodilation
  • blood shift
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18
Q

What can the lungs do to maintain tissue oxygenation in anaemia?

A

Increased respiratory rate

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19
Q

What can the heart do to maintain tissue oxygenation in anaemia?

A
  • increase pulse rate
  • increase cardiac output
  • increase blood flow
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20
Q

What does an increase in 2,3 DPG cause which helps maintain tissue oxygenation?

A

Increased O2 dissociation

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21
Q

What does increased production of erythropoietin by the kidneys cause?

A

Results in increased erythropoiesis in the bone marrow so more RBCs

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22
Q

Which adaptation to anaemia is more marked in acute anaemia than chronic anaemia?

A

Increased respiratory rate

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23
Q

What are the parameters that affect the adaptation mechanisms to anaemia?

A
  • underlying conditions
  • acute or chronic anaemia
  • transfusion of RBC?
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24
Q

What types of underlying conditions impair the adaptation mechanisms to anaemia?

A

Anything that affects the cardiac output, arterial blood flow, O2 saturation of Hb etc eg. cardiovascular disease, respiratory disease, age

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25
Q

Why do we transfuse red blood cells?

A

To restore oxygen-carrying capacity

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26
Q

What are the triggers indicating red blood cell transfusion?

A

-

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27
Q

What are the alternative methods to RBC transfusion?

A
  • correction of treatable causes of anaemia

- correction of coagulopathy

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28
Q

Correction of treatable causes of anaemia is an alternative to RBC transfusion. Give examples

A
  • iron deficiency
  • B12 and folate deficiency
  • erythropoietin treatment for patients with renal disease
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29
Q

Correction of coagulopathy is an alternative to RBC transfusion. Give examples

A
  • discontinuation of antiplatelet agents

- administration of anti-fibrinolytic agents

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30
Q

What is coagulopathy?

A

A condition in which the blood’s ability to clot is impaired. This condition can cause prolonged or excessive bleeding

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31
Q

What is the % reduction in blood volume and mL+ in a class I haemorrhage?

A

less than 15%

less than 750

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32
Q

What is the % reduction in blood volume and mL+ in a class II haemorrhage?

A

15-30%

750-1500

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33
Q

What is the % reduction in blood volume and mL+ in a class III haemorrhage?

A

30-40%

1500-2000

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34
Q

What is the % reduction in blood volume and mL+ in a class IV haemorrhage?

A

over 40%

over 2000

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35
Q

For which classes of haemorrhage is a transfusion indicated?

A

Class III and class IV

class III = probably necessary
class IV = necessary
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36
Q

An alternative to transfusion is cell salvage. What is this?

A

Also known as autologous blood transfusion, is a medical procedure involving recovering blood lost during surgery and re-infusing it into the patient

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37
Q

Haemorrhage leads to which type of anaemia?

A

Acute anaemia

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38
Q

What are the objectives for patients on regular transfusions due to myeloid failure syndromes?

A
  • symptomatic relief of anaemia
  • improvement of quality of life
  • prevention of ischaemic organ damage
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39
Q

What is the transfusion target for patients on chronic transfusion programmes due to myeloid failure syndromes?

A

Hb 8-10g/dl

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40
Q

What are the normal haemoglobin levels?

A

Male = 13.8 to 17.2 grams per deciliter (g/dL)

Female = 12.1 to 15.1 g/dL

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41
Q

The transfusion target should be tailored for each patient with chronic anaemia due to myeloid failure syndromes. What must be taken into consideration?

A
  • co-morbidities that affect cardiac and respiratory function
  • risk of iron overload
  • adaptation mechanisms to anaemia developed
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42
Q

What are the objectives for patients on regular transfusions due to inherited anaemias (thalassaemia)?

A
  • suppression of endogenous erythropoiesis
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43
Q

What are the threshold and target Hb levels for patients on regular transfusions due to inherited anaemias (thalassaemia)?

A

Threshold = 90-95

Target = 100-120g/L

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44
Q

What must be taken into consideration when transfusing patients who have inherited anaemias (thalassaemia)?

A

Iron overload

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45
Q

Patients with thalassaemia may due from the complications of iron overload including..

A
  • cardiomyopathy

- liver failure

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46
Q

What is iron chelation? (needed by patients with thalassaemia)

A

Drug therapy for iron overload

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47
Q

What is haemachromatosis?

A

An inherited disorder in which iron levels in the body slowly build up over many years - sometimes called iron overload disorder

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48
Q

The transfusion threshold in thalassaemia major is Hb 9-9.5. Why?

A

To guarantee a balance between bone marrow suppression and iron overload

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49
Q

How you would you treat a 56 year old male who developed end stage renal disease drop the Hb 12.3 g/L to 9.6 g/dL over the last 3 months and an MCV of 80 fL?

A

Erythropoietin therapy - an EPO production is impaired in renal disease

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50
Q

How are platelets stored?

A
  • stored at “room temperature” (22 degrees C)

- shelf-life is 5 days from collection

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51
Q

What is the “adult therapeutic dose” of platelets?

A

Platelets from 4 pooled donations (or equivalent number from a single apheresis donation)

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52
Q

What is an apheresis donation?

A

During a plasma apheresis donation, the blood is collected by a machine, which separates the plasma, red cells and platelets and returns the red cells and/or platelets back to the donor

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53
Q

What is the usual transfusion time for platelets?

A

30 mins/unit

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54
Q

Why do we transfuse platelets?

A
  • treatment of bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
  • prevention of bleeding
55
Q

What are the contraindications to platelet transfusion?

A
  • heparin induced thrombocytopenia and thrombosis

- thrombotic thrombocytopenic purpura

56
Q

What are the guidelines for platelet transfusion as treatment in massive haemorrhage?

A

Keep platelet count above 75x10^9/l

57
Q

What are the guidelines for platelet transfusion as treatment for bone marrow failure?

A

Keep platelet count above 10x10^9/l

or above 20x10^9/l if there is an additional risk eg. sepsis

58
Q

What are the guidelines for platelet transfusion as prophylaxis for surgery?

A

Minor procedures = aim for 50x10^9/l

Major surgery = aim for 80x10^9/l

CNS or eye surgery = 100x10^9/l

59
Q

What is the limiting factor for shelf life of platelets?

A

The risk of contamination by bacteria from donor’s arm that grow at the conditions of storage (22 degrees) and can be transmitted to the recipient

60
Q

What is the normal platelet count?

A

A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood

61
Q

How is fresh frozen plasma (FFP) stored?

A
  • stored at -30 degrees C for up to 24 months

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

62
Q

What is the usual dose of fresh frozen plasma (FFP)?

A

12-15mL/kg (4-6 units for average adult)

63
Q

What is the usual transfusion time for fresh frozen plasma (FFP)?

A

30 mins/unit

64
Q

What are the main indications for FFP transfusion?

A
  • coagulopathy with bleeding/surgery (prevent bleeding)
  • massive haemorrhage (treat bleeding)
  • thrombotic thrombocytopenic purpura
65
Q

You should not used FFP transfusion in what circumstances?

A
  • for warfarin reversal (to treat warfarin overdose)

- for replacement of single factor deficiency

66
Q

What should you use for emergency reversal of life-threatening warfarin over-anticoagulation?

A

Prothrombin complex concentrate (PCC)

67
Q

Which clotting factors does prothrombin complex concentrate (PCC) contain? (used for warfarin reversal)

A

All of the vitamin K dependent factors

  • factor II
  • factor VII
  • factor IX
  • factor X

Derived from fresh frozen plasma

68
Q

Name 2 types of blood transfusion for patients with specific requirements

A
  • CMV negative

- irradiated

69
Q

What is the purpose of CMV negative blood transfusions?

A

To keep at-risk patients safe from developing CMV infection (50% of us are CMV negative)

70
Q

Who requires CMV negative blood?

A
  • children under 1
  • intrauterine transfusions
  • congenital immunodeficiency
  • pregnant women having elective transfusion UNLESS known to be CMV IgG +ve
71
Q

What is the purpose of irradiated blood transfusions?

A

To prevent transfusion-associated graft versus host disease (rare but fatal) in specific T-cell immunodeficiency cases

72
Q

Who requires irradiated blood transfusions?

A
  • intrauterine transfusions
  • congenital immunodeficiency
  • Hodgkin lymphoma
  • stem cell/marrow transplant patients
  • after purine analogue chemotherapy eg. fludarabine
73
Q

Describe the first stages of pre-tranfusion lab testing of blood

A
  • determination of ABO and Rh(D) group

- patient’s plasma “screened” for antibodies against other clinically significant blood group antigens

74
Q

What happens if after plasma is screened for other antibodies, the test is negative?

A

No further testing

75
Q

What happens if after the plasma is screen for other antibodies, the test is positive?

A

Antibody identification - testing the patient’s plasma against a plasma of red cells expressing all the clinically significant blood groups, using the Antiglobulin Test

76
Q

What happens after the donor red cells of the correct ABO and Rh group are selected from the blood bank?

A

Crossmatching

77
Q

What is done in crossmatching?

A

Patients plasma is mixed with aliquots of donor red cells to see if a reaction (agglutination or haemolysis) occurs

78
Q

If there is no reaction during crossmatching, what does this mean?

A

RBC units are compatible and there is no risk of acute haemolysis

79
Q

If there is a reaction (agglutination or haemolysis) during crossmatching, what does this mean?

A

RBC units are incompatible and there is a risk of acute haemolysis

80
Q

What are the potential immunological acute transfusion reactions?

A
  • acute haemolytic transfusion reaction (ABO incompatibility)
  • allergic/anaphylactic reaction
  • TRALI (transfusion-related acute lung injury)
81
Q

What are the potential non-immunological acute transfusion reactions?

A
  • bacterial contamination
  • TACO (transfusion associated circulatory overload)
  • febrile non-haemolytic transfusion reaction
82
Q

What are the immunological delayed transfusion reactions?

A
  • transfusion-associated graft-versus-host disease (TA-GvHD)

- post transfusion purpura

83
Q

What are the non-immunological delayed transfusion reactions?

A

Transfusion Transmitted infection (TTI) - viral//prion

84
Q

What defines an ACUTE transfusion reaction?

A

Present less than 24 hours after transfusion

85
Q

What defines a DELAYED transfusion reaction?

A

Present more than 24 hours after transfusion

86
Q

What is risk of infection of Hep B per unit of blood?

A

1.5 in 1 million

87
Q

What is the risk of infection of HIV per unit of blood?

A

1 in 6 million

88
Q

What is the risk of infection of Hep C per unit of blood?

A

1 in 30 million

89
Q

Many steps are taking to reduce the risk of transmission of Prion Disease by blood. What are they?

A
  • leucodepletion (1998)
  • UK plasma not used for fractionation
  • imported FFP for all patients born after 1996 (imported from prion disease-free countries)
90
Q

Is oozing from venepuncture site a sign of transfusion reaction?

A

Yes

91
Q

What happens in an acute haemolytic reaction (ABO incompatibility)?

A
  • release of free Hb
  • deposition of Hb in distal renal tubule = acute renal failure
  • stimulation of coagulation = microvascular thrombosis
  • stimulation of cytokine storm
  • scavenges NO = generalised vasoconstriction
92
Q

What are the signs and symptoms of acute haemolytic reaction?

A
  • fever and chills
  • back pain
  • pain at infusion site
  • hypotension/shock
  • haemoglobinuria
  • increased bleeding due to DIC
  • chest pain due to ischaemia
  • sense of impending death
93
Q

When do acute haemolytic reactions occur?

A

Severe reaction may occur early in the transfusion, within the first 15 min

Milder reactions may occur later but usually before the end of transfusion

94
Q

How often are acute haemolytic reactions fatal?

A

20-30%

95
Q

The symptoms of acute haemolytic reactions are due to what?

A

Intravascular free haemoglobin - cytotoxic effects

96
Q

The cause of acute haemolytic reaction/ ABO incompatibility is always what?

A

A human error

97
Q

15% of errors causing acute haemolytic reaction are due to what?

A

Errors in patient identification

98
Q

50% of errors causing acute haemolytic reactions are due to what?

A

Final administration checks/ monitoring of patient/ complete documentation

99
Q

Other human errors leading to acute haemolytic reaction may occur during what?

A
  • sample labelling
  • compatibility procedures
  • product release
  • storage
  • request form
100
Q

What should be done during sample labelling to prevent acute haemolytic reaction?

A
  • label at the bedside
  • check details against patient’s identification wristband
  • do not use addressograph labels
101
Q

What should be done during pre-administration checks to prevent acute haemolytic reactions?

A

Check patient’s details on the compatibility label against the patient’s wristband at the bedside

102
Q

When do delayed haemolytic reactions tend to occur?

A

Onset 3-14 days following transfusion of RBC

103
Q

What are the clinical features of delayed haemolytic reaction?

A
  • fatigue
  • jaundice
  • and/or fever
104
Q

What are the laboratory findings in delayed haemolytic reaction?

A
  • drop in Hb
  • increased LDH
  • increased indirect bilirubin
  • positive Direct antiglobulin test
105
Q

What are delayed haemolytic reactions due to?

A

Immune IgG antibodies against RBC antigens other than ABO

- the antibodies are formed after the transfusion

106
Q

What are some other blood group systems other than ABO and Rhesus?

A
  • Kell
  • Duffy
  • Kidd
  • Lutheran
  • MNS
  • Lewis
107
Q

What are the alternative names for the Coomb’s test?

A
  • Anti-human globulin test (AHG)

- Direct anti-globulin test (DAT)

108
Q

What happens in the Coomb’s test?

A

Red cells are incubated with AHG (a reagent that contains antibodies against human IgG) - if they red cells have IgG antibody eg. anti-Rh in Rh positive patient, the cells will agglutinate = positive test

109
Q

What is the Coomb’s test/anti-human globulin test used to detect?

A

IgG antibodies on red cells - it is a key test in blood transfusion

110
Q

What = positive test in Coomb’s test?

A

Visible agglutination

111
Q

How is transfusion-related acute lung injury (TRALI) caused?

A
  • donor has antibodies to recipient’s leucocytes (anti-HLA or anti-HNA)
  • activated WBCs lodge in pulmonary capillaries
  • they release substances that cause endothelial damage and capillary leak
112
Q

What is the rate of fatalities in transfusion-related acute lung injury?

A

5-10%

113
Q

Transfusion-related acute lung injury almost always complicates transfusion of which components?

A

Plasma-rich components eg. platelets, FFP

114
Q

What is the criteria for diagnosis of TRALI?

A
  • sudden onset of acute lung injury occurring 6 hours of a transfusion
  • acute lung injury = hypoxaemia, new bilateral CXR infiltrates, no evidence of volume overload
115
Q

How is TRALI treated?

A
  • supportive
  • mild forms = may respond to supplemental oxygen therapy
  • severe forms = may require mechanical ventilation and ICU support
  • no role for diuretics or corticosteroids
116
Q

Do patients recover from TRALI?

A

The majority of patients recover within 72-96 hours

117
Q

What are the laboratory investigations into TRALI?

A
  • donor is tested for HLA and granulocyte antibodies

- recipient is tested for expression of neutrophil antigens

118
Q

What is the key thing to confirm a diagnosis of TRALI?

A

Donor has antibodies against antigens that are expressed on recipient’s granulocytes

119
Q

How does transfusion-associated circulatory overload (TACO) present?

A
  • sudden dyspnoea
  • orthopnoea
  • tachycardia
  • hypertension
  • hypoxaemia
  • raised BP
  • elevated JVP
120
Q

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

A
  • elderly
  • small children
  • compromised left ventricular function
  • increased volume of transfusion
  • increased rate of transfusion
121
Q

What is the significant type of blood component in TRALI vs TACO?

A

TRALI = usually plasma or platelets

TACO = any

122
Q

What is the BP in TRALI vs TACO?

A

TRALI = often reduced

TACO = often raised

123
Q

What is the temperature in TRALI vs TACO?

A

TRALI = often raised

TACO = normal

124
Q

What are the echo results in TRALI vs TACO?

A

TRALI = normal

TACO = abnormal

125
Q

What is the effect of diuretics in TRALI vs TACO?

A

TRALI = worsen

TACO = improve

126
Q

What is the effect of fluid loading in TRALI vs TACO?

A

TRALI = improves

TACO = worsens

127
Q

Name 2 types of allergic reaction that can occur in transfusion

A
  • urticarial rash +/- wheeze

- anaphylaxis

128
Q

How is urticarial rash +/- wheeze cause in transfusion?

A

Hypersensitivity to a random plasma protein - often not severe

129
Q

What are the signs/symptoms of anaphylaxis after transfusion?

A

Severe, life-threatening reaction soon after transfusion started

  • wheeze/asthma
  • increased pulse
  • decreased BP (shock)
  • laryngeal oedema/facial oedema
130
Q

What laboratory investigations are done when anaphylaxis after transfusion occurs?

A

Quantification of IgA, testing for anti-IgA antibodies

131
Q

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

A
  • antibodies directed against donor leukocytes and HLA antigens. (in contrast to TRALI which is the other way round)
  • can also be due to cytokines and other biologically active molecules that accumulate during storage of blood components
132
Q

What are the signs/symptoms of FNHTR?

A

During or soon after transfusion

  • fever (rise in temp more than 1 C +/- shakes and rigors)
  • may have increased pulse

Unpleasant but not life threatening (self-limited reaction)

133
Q

Why do febrile non-haemolytic transfusion reactions occur less often now?

A

Due to leucodepletion of blood and platelets

134
Q

What should you do in the case of FNHTR?

A

Discontinue transfusion until you exclude ‘wrong blood’ or bacterial infection

8. CP - Core Haematology (11 decks)

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