Blood Transfusions Flashcards
A sample of blood from donation will undergo testing for what conditions?
HIV, Hep B, C and E, HTLV and syphilis
How many donors do blood components come from? Give some examples of these?
1 donor - red cells, FFP, platelets and cryoprecipitate
How many donors do blood products come from? Give some examples of these?
Up to 20,000 donors - anti-D immunoglobulin and prothrombin complex concentrate
What is cryoprecipitate?
A source of fibrinogen
What is Anti-D immunoglobulin used for?
Rhesus disease
What is prothrombin complex concentrate used for?
Warfarin reversal
What are responsible for determining our blood groups?
Antigens on the red cell surface
Our immune system normally ignores the antigens on our red cell surface. However, if we are exposed to antigens which are foreign - what happens?
Our bodies will forms antibodies against these antigens, which can be problematic if we encounter the same antigen again
What are some examples of how we could become exposed to foreign blood related antigens?
Blood transfusions or Rhesus disease
The antigens on our blood cells are determined from where?
Blood cell antigen genes which we get from our parents
The ABO system is coded for where?
On chromosome 9
In the ABO system, what relationship do A and B have over O?
They are dominant
In the ABO system, what relationship do A and B have with each other?
They are co-dominant
In the ABO system, O is silent. What does this mean?
There is no O antigen, just an absence of A or B
What could be the genotype of someone who was blood group O?
OO
What could be the genotype of someone who was blood group A?
AA or AO
What could be the genotype of someone who was blood group B?
BB or BO
What could be the genotype of someone who was blood group AB?
AB
What is Landsteiner’s law?
When an individual lacks the A or B antigen, the corresponding IgM antibody is present in their plasma
If an individual who had antibodies against A or B antigen were to be exposed to those antigens, what would happen?
There would be haemolysis of the red cells that expressed that antigen
If antibodies against A and B antigens are going to be produced - when does this happen?
As early as 6 months of age
What could be the genotype of someone who is rhesus positive?
DD or Dd
What could be the genotype of someone who is rhesus negative?
dd
What are the aims of pre-transfusion testing?
To identify the ABO and RhD group of a patient, and to identify the presence of any clinically significant red cell antibodies
What is the most common way to identify an individual’s blood group?
Group and save
What is the first step of ABO and Rh grouping of blood?
Use antisera reagent with a known antibody specificity to identify antigens present on the red cell
When doing ABO and Rh grouping, if an antigen is present on a red cell, what happens?
The corresponding IgM antibody (in the reagent) will bind to the antigen and result in agglutination
What is the second step of ABO and Rh grouping of blood?
Use reagent red cells with known antigen specificity to identify antibodies present in the plasma
Antibodies to most things other than ABO and Rh are IgG antibodies which do not cause agglutination in the way that IgM does. What is added to the antibody/antigen complex to make the results of this test more obvious?
Anti-human globulin
What investigation is performed to check that donor cells are compatible with patient plasma?
Crossmatch
When doing a crossmatch, what would indicate that the donor cells are incompatible with the patient’s plasma?
Agglutination
What are the reasons for doing a red cell transfusion?
Symptomatic anaemia with Hb < 70g/L OR major bleeding
How should red cell transfusions be given?
Give one unit and reassess before giving another
What are the reasons for a platelet transfusion?
Prophylaxis in patients with bone marrow failure, treatment of bleeding in thrombocytopenic patients, prophylaxis prior to surgery/procedures in a thrombocytopenic patient
How should platelet transfusions be given?
Give one unit and reassess before giving another
How many units of platelets are needed for prophylaxis?
One
FFP transfusion contains what?
Clotting factors
Why would you give an FFP transfusion?
Treatment of bleeding or prophylaxis prior to surgery/procedures in patients with a coagulopathy OR management of a massive haemorrhage
Samples for blood transfusion should be sent off in what colour of tube?
Pink
How often should observations be taken during a blood transfusion?
Every 15 minutes throughout
If a patient becomes unwell or deteriorates during a blood transfusion, what should you do?
Pause the transfusion and investigate
What are some symptoms of an acute transfusion reaction?
Rigors, rash/flushing, feeling of impending doom, collapse, loin pain
What are some signs of an acute transfusion reaction?
Fever, tachycardia, hypotension, respiratory distress
ABO incompatible transfusion reactions are the most serious to occur. What does this lead to?
Intravascular haemolysis of the transfused cells
How should a bacterial contaminant of a blood component be treated?
Supportively, and give broad spectrum antibiotics
What are some clinical features of a transfusion associated circulatory overload?
Respiratory distress (within 6 hours), raised BP, raised JVP
What are some risk factors for a transfusion associated circulatory overload?
Elderly patient, cardiac failure, renal impairment
How is transfusion associated circulatory overload treated?
Supportive therapy and diuretics
What are some defining features of mild transfusion reactions?
An isolated temperature rise to > 38 degrees or a rise in temperature by 1-2 degrees OR an isolated rash
What is the management of a mild transfusion reaction?
Continue the transfusion but consider slowing the rate, give paracetamol or anti-histamine depending on the cause and monitor closely
What are some subtypes of mild transfusion reactions?
Febrile non-haemolytic transfusion reactions / mild allergic reactions
In delayed haemolytic transfusion reactions, the patient mounts a delayed immune response to the red cell antigen - antibodies are usually what type?
IgG
What type of haemolysis occurs in delayed haemolytic transfusion reactions? When does it occur?
Extravascular / 5-10 days post-transfusion
What test will be positive in delayed haemolytic transfusion reactions? What will it show?
DAT - detection of alloantibody
