(36) Blood transfusion Flashcards
1
Q
What is leucodepletion?
A
Whole blood is filtered to remove white blood cells
2
Q
What are the 3 main contents of whole blood after leucodepletion?
A
- red blood cells
- platelets
- plasma
3
Q
What is cryoprecipitate?
A
Frozen blood product prepared from plasma.
- fresh frozen plasma is centrifuged and the precipitate collected
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
5
Q
Give examples of components of plasma separated out during fractionation
A
- factor concentrates (FVIII, FIX, prothrombin complex)
- albumin
- immunoglobin
6
Q
What is the usual transfusion time? (1 unit RBC)
A
1.5-3 hours
7
Q
How is RBC for transfusion stored?
A
At 4 degrees C for up to 35 days from collection
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
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
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
11
Q
The symptoms of anaemia are due to what?
A
Tissue hypoxia
12
Q
What is the transfusion threshold (trigger)?
A
The lowest concentration of Hb that is not associated with symptoms of anaemia
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
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
15
Q
What can the kidneys do to maintain tissue oxygenation in anaemia?
A
Increased erythropoietin release
16
Q
What can the bone marrow do to maintain tissue oxygenation in anaemia?
A
Increase erythropoiesis
17
Q
What can the peripheral organs do to maintain tissue oxygenation in anaemia?
A
- decrease tissue pH
- increase O2 extraction
- vasodilation
- blood shift
18
Q
What can the lungs do to maintain tissue oxygenation in anaemia?
A
Increased respiratory rate
19
Q
What can the heart do to maintain tissue oxygenation in anaemia?
A
- increase pulse rate
- increase cardiac output
- increase blood flow
20
Q
What does an increase in 2,3 DPG cause which helps maintain tissue oxygenation?
A
Increased O2 dissociation
21
Q
What does increased production of erythropoietin by the kidneys cause?
A
Results in increased erythropoiesis in the bone marrow so more RBCs
22
Q
Which adaptation to anaemia is more marked in acute anaemia than chronic anaemia?
A
Increased respiratory rate
23
Q
What are the parameters that affect the adaptation mechanisms to anaemia?
A
- underlying conditions
- acute or chronic anaemia
- transfusion of RBC?
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
25
Why do we transfuse red blood cells?
To restore oxygen-carrying capacity
26
What are the triggers indicating red blood cell transfusion?
-
27
What are the alternative methods to RBC transfusion?
- correction of treatable causes of anaemia
| - correction of coagulopathy
28
Correction of treatable causes of anaemia is an alternative to RBC transfusion. Give examples
- iron deficiency
- B12 and folate deficiency
- erythropoietin treatment for patients with renal disease
29
Correction of coagulopathy is an alternative to RBC transfusion. Give examples
- discontinuation of antiplatelet agents
| - administration of anti-fibrinolytic agents
30
What is coagulopathy?
A condition in which the blood's ability to clot is impaired. This condition can cause prolonged or excessive bleeding
31
What is the % reduction in blood volume and mL+ in a class I haemorrhage?
less than 15%
less than 750
32
What is the % reduction in blood volume and mL+ in a class II haemorrhage?
15-30%
750-1500
33
What is the % reduction in blood volume and mL+ in a class III haemorrhage?
30-40%
1500-2000
34
What is the % reduction in blood volume and mL+ in a class IV haemorrhage?
over 40%
over 2000
35
For which classes of haemorrhage is a transfusion indicated?
Class III and class IV
```
class III = probably necessary
class IV = necessary
```
36
An alternative to transfusion is cell salvage. What is this?
Also known as autologous blood transfusion, is a medical procedure involving recovering blood lost during surgery and re-infusing it into the patient
37
Haemorrhage leads to which type of anaemia?
Acute anaemia
38
What are the objectives for patients on regular transfusions due to myeloid failure syndromes?
- symptomatic relief of anaemia
- improvement of quality of life
- prevention of ischaemic organ damage
39
What is the transfusion target for patients on chronic transfusion programmes due to myeloid failure syndromes?
Hb 8-10g/dl
40
What are the normal haemoglobin levels?
Male = 13.8 to 17.2 grams per deciliter (g/dL)
Female = 12.1 to 15.1 g/dL
41
The transfusion target should be tailored for each patient with chronic anaemia due to myeloid failure syndromes. What must be taken into consideration?
- co-morbidities that affect cardiac and respiratory function
- risk of iron overload
- adaptation mechanisms to anaemia developed
42
What are the objectives for patients on regular transfusions due to inherited anaemias (thalassaemia)?
- suppression of endogenous erythropoiesis
43
What are the threshold and target Hb levels for patients on regular transfusions due to inherited anaemias (thalassaemia)?
Threshold = 90-95
Target = 100-120g/L
44
What must be taken into consideration when transfusing patients who have inherited anaemias (thalassaemia)?
Iron overload
45
Patients with thalassaemia may due from the complications of iron overload including..
- cardiomyopathy
| - liver failure
46
What is iron chelation? (needed by patients with thalassaemia)
Drug therapy for iron overload
47
What is haemachromatosis?
An inherited disorder in which iron levels in the body slowly build up over many years - sometimes called iron overload disorder
48
The transfusion threshold in thalassaemia major is Hb 9-9.5. Why?
To guarantee a balance between bone marrow suppression and iron overload
49
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?
Erythropoietin therapy - an EPO production is impaired in renal disease
50
How are platelets stored?
- stored at "room temperature" (22 degrees C)
| - shelf-life is 5 days from collection
51
What is the "adult therapeutic dose" of platelets?
Platelets from 4 pooled donations (or equivalent number from a single apheresis donation)
52
What is an apheresis donation?
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
53
What is the usual transfusion time for platelets?
30 mins/unit
54
Why do we transfuse platelets?
- treatment of bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
- prevention of bleeding
55
What are the contraindications to platelet transfusion?
- heparin induced thrombocytopenia and thrombosis
| - thrombotic thrombocytopenic purpura
56
What are the guidelines for platelet transfusion as treatment in massive haemorrhage?
Keep platelet count above 75x10^9/l
57
What are the guidelines for platelet transfusion as treatment for bone marrow failure?
Keep platelet count above 10x10^9/l
or above 20x10^9/l if there is an additional risk eg. sepsis
58
What are the guidelines for platelet transfusion as prophylaxis for surgery?
Minor procedures = aim for 50x10^9/l
Major surgery = aim for 80x10^9/l
CNS or eye surgery = 100x10^9/l
59
What is the limiting factor for shelf life of platelets?
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
What is the normal platelet count?
A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood
61
How is fresh frozen plasma (FFP) stored?
- stored at -30 degrees C for up to 24 months
| - thawed immediately before use (takes 20-30 mins)
62
What is the usual dose of fresh frozen plasma (FFP)?
12-15mL/kg (4-6 units for average adult)
63
What is the usual transfusion time for fresh frozen plasma (FFP)?
30 mins/unit
64
What are the main indications for FFP transfusion?
- coagulopathy with bleeding/surgery (prevent bleeding)
- massive haemorrhage (treat bleeding)
- thrombotic thrombocytopenic purpura
65
You should not used FFP transfusion in what circumstances?
- for warfarin reversal (to treat warfarin overdose)
| - for replacement of single factor deficiency
66
What should you use for emergency reversal of life-threatening warfarin over-anticoagulation?
Prothrombin complex concentrate (PCC)
67
Which clotting factors does prothrombin complex concentrate (PCC) contain? (used for warfarin reversal)
All of the vitamin K dependent factors
- factor II
- factor VII
- factor IX
- factor X
Derived from fresh frozen plasma
68
Name 2 types of blood transfusion for patients with specific requirements
- CMV negative
| - irradiated
69
What is the purpose of CMV negative blood transfusions?
To keep at-risk patients safe from developing CMV infection (50% of us are CMV negative)
70
Who requires CMV negative blood?
- children under 1
- intrauterine transfusions
- congenital immunodeficiency
- pregnant women having elective transfusion UNLESS known to be CMV IgG +ve
71
What is the purpose of irradiated blood transfusions?
To prevent transfusion-associated graft versus host disease (rare but fatal) in specific T-cell immunodeficiency cases
72
Who requires irradiated blood transfusions?
- intrauterine transfusions
- congenital immunodeficiency
- Hodgkin lymphoma
- stem cell/marrow transplant patients
- after purine analogue chemotherapy eg. fludarabine
73
Describe the first stages of pre-tranfusion lab testing of blood
- determination of ABO and Rh(D) group
| - patient's plasma "screened" for antibodies against other clinically significant blood group antigens
74
What happens if after plasma is screened for other antibodies, the test is negative?
No further testing
75
What happens if after the plasma is screen for other antibodies, the test is positive?
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
What happens after the donor red cells of the correct ABO and Rh group are selected from the blood bank?
Crossmatching
77
What is done in crossmatching?
Patients plasma is mixed with aliquots of donor red cells to see if a reaction (agglutination or haemolysis) occurs
78
If there is no reaction during crossmatching, what does this mean?
RBC units are compatible and there is no risk of acute haemolysis
79
If there is a reaction (agglutination or haemolysis) during crossmatching, what does this mean?
RBC units are incompatible and there is a risk of acute haemolysis
80
What are the potential immunological acute transfusion reactions?
- acute haemolytic transfusion reaction (ABO incompatibility)
- allergic/anaphylactic reaction
- TRALI (transfusion-related acute lung injury)
81
What are the potential non-immunological acute transfusion reactions?
- bacterial contamination
- TACO (transfusion associated circulatory overload)
- febrile non-haemolytic transfusion reaction
82
What are the immunological delayed transfusion reactions?
- transfusion-associated graft-versus-host disease (TA-GvHD)
| - post transfusion purpura
83
What are the non-immunological delayed transfusion reactions?
Transfusion Transmitted infection (TTI) - viral//prion
84
What defines an ACUTE transfusion reaction?
Present less than 24 hours after transfusion
85
What defines a DELAYED transfusion reaction?
Present more than 24 hours after transfusion
86
What is risk of infection of Hep B per unit of blood?
1.5 in 1 million
87
What is the risk of infection of HIV per unit of blood?
1 in 6 million
88
What is the risk of infection of Hep C per unit of blood?
1 in 30 million
89
Many steps are taking to reduce the risk of transmission of Prion Disease by blood. What are they?
- leucodepletion (1998)
- UK plasma not used for fractionation
- imported FFP for all patients born after 1996 (imported from prion disease-free countries)
90
Is oozing from venepuncture site a sign of transfusion reaction?
Yes
91
What happens in an acute haemolytic reaction (ABO incompatibility)?
- 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
What are the signs and symptoms of acute haemolytic reaction?
- 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
When do acute haemolytic reactions occur?
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
How often are acute haemolytic reactions fatal?
20-30%
95
The symptoms of acute haemolytic reactions are due to what?
Intravascular free haemoglobin - cytotoxic effects
96
The cause of acute haemolytic reaction/ ABO incompatibility is always what?
A human error
97
15% of errors causing acute haemolytic reaction are due to what?
Errors in patient identification
98
50% of errors causing acute haemolytic reactions are due to what?
Final administration checks/ monitoring of patient/ complete documentation
99
Other human errors leading to acute haemolytic reaction may occur during what?
- sample labelling
- compatibility procedures
- product release
- storage
- request form
100
What should be done during sample labelling to prevent acute haemolytic reaction?
- label at the bedside
- check details against patient's identification wristband
- do not use addressograph labels
101
What should be done during pre-administration checks to prevent acute haemolytic reactions?
Check patient's details on the compatibility label against the patient's wristband at the bedside
102
When do delayed haemolytic reactions tend to occur?
Onset 3-14 days following transfusion of RBC
103
What are the clinical features of delayed haemolytic reaction?
- fatigue
- jaundice
- and/or fever
104
What are the laboratory findings in delayed haemolytic reaction?
- drop in Hb
- increased LDH
- increased indirect bilirubin
- positive Direct antiglobulin test
105
What are delayed haemolytic reactions due to?
Immune IgG antibodies against RBC antigens other than ABO
| - the antibodies are formed after the transfusion
106
What are some other blood group systems other than ABO and Rhesus?
- Kell
- Duffy
- Kidd
- Lutheran
- MNS
- Lewis
107
What are the alternative names for the Coomb's test?
- Anti-human globulin test (AHG)
| - Direct anti-globulin test (DAT)
108
What happens in the Coomb's test?
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
What is the Coomb's test/anti-human globulin test used to detect?
IgG antibodies on red cells - it is a key test in blood transfusion
110
What = positive test in Coomb's test?
Visible agglutination
111
How is transfusion-related acute lung injury (TRALI) caused?
- 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
What is the rate of fatalities in transfusion-related acute lung injury?
5-10%
113
Transfusion-related acute lung injury almost always complicates transfusion of which components?
Plasma-rich components eg. platelets, FFP
114
What is the criteria for diagnosis of TRALI?
- 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
How is TRALI treated?
- 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
Do patients recover from TRALI?
The majority of patients recover within 72-96 hours
117
What are the laboratory investigations into TRALI?
- donor is tested for HLA and granulocyte antibodies
| - recipient is tested for expression of neutrophil antigens
118
What is the key thing to confirm a diagnosis of TRALI?
Donor has antibodies against antigens that are expressed on recipient's granulocytes
119
How does transfusion-associated circulatory overload (TACO) present?
- sudden dyspnoea
- orthopnoea
- tachycardia
- hypertension
- hypoxaemia
- raised BP
- elevated JVP
120
What are the risk factors for transfusion-associated circulatory overload (TACO)?
- elderly
- small children
- compromised left ventricular function
- increased volume of transfusion
- increased rate of transfusion
121
What is the significant type of blood component in TRALI vs TACO?
TRALI = usually plasma or platelets
TACO = any
122
What is the BP in TRALI vs TACO?
TRALI = often reduced
TACO = often raised
123
What is the temperature in TRALI vs TACO?
TRALI = often raised
TACO = normal
124
What are the echo results in TRALI vs TACO?
TRALI = normal
TACO = abnormal
125
What is the effect of diuretics in TRALI vs TACO?
TRALI = worsen
TACO = improve
126
What is the effect of fluid loading in TRALI vs TACO?
TRALI = improves
TACO = worsens
127
Name 2 types of allergic reaction that can occur in transfusion
- urticarial rash +/- wheeze
| - anaphylaxis
128
How is urticarial rash +/- wheeze cause in transfusion?
Hypersensitivity to a random plasma protein - often not severe
129
What are the signs/symptoms of anaphylaxis after transfusion?
Severe, life-threatening reaction soon after transfusion started
- wheeze/asthma
- increased pulse
- decreased BP (shock)
- laryngeal oedema/facial oedema
130
What laboratory investigations are done when anaphylaxis after transfusion occurs?
Quantification of IgA, testing for anti-IgA antibodies
131
What is febrile non-haemolytic transfusion reactions (FNHTR)?
- 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
What are the signs/symptoms of FNHTR?
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
Why do febrile non-haemolytic transfusion reactions occur less often now?
Due to leucodepletion of blood and platelets
134
What should you do in the case of FNHTR?
Discontinue transfusion until you exclude 'wrong blood' or bacterial infection
