BLOOD TRANSFUSIONS Flashcards
What are the blood components used in transfusion?
Red cells Platelets Fresh frozen plasma Cryoprecipitate Human albumin solution Intravenous immunoglobulin Prothrombin complex concentrate
What volume of red cells per kg are needed to increase the Hb by 1g?
3ml/kg
What is the volume of a unit of red cells?
280 ml
What increase in Hb would you expect to see having given an adult a unit of red cells?
More than 1g/dL
At what temperature are donated red blood cells kept at?
4˚
How long can donated red blood cells be stored for?
35 days
What is the group of blood cells that can be transfused to anyone in an emergency?
O Rh-
If there was no O negative available but you had not had time to fully crossmatch the patient, what would you give them?
Group specific blood
What are the indications for red cell transfusion?
Active bleeding where fluids are unlikely to be sufficient
Bone marrow failure
Abnormal red cells need suppressing or exchanging (eg Hb SS or thalassaemia)
Rarely given for deficiency anaemias such as iron or folate.
How many donors are required to make one unit of platelets?
4
What is platelet apheresis?
When only the platelets are taken from a donor. The machine they are hooked up to returns the other blood components.
How would you check at the bedside that you were giving a good product of platelets?
Shake the bag to check for flocules.
What temperature are platelets kept at?
22˚
How long can donated platelets be stored for?
7 days
Why can platelets be a more common source of infection than other blood products?
Because they are kept at room temperature
Do you need to crossmatch platelets for transfusion?
No, only need to know blood group
What are the indications for transfusing platelets?
Preventing bleeding in those with thrombocytopenia (eg about to undergo surgery, or leukaemia)
Stopping bleeding in those with thrombocytopenia
What is the standard dose of platelets for transfusion?
Either 10ml/kg or 1 pool (4 donations) - whichever is smaller. Very rarely need more.
How much donated fresh frozen plasma is contained within 1 unit?
About 300 ml (from 1 donor)
What temperature is donated fresh frozen plasma stored at?
-30˚
How long can donated fresh frozen plasma be stored for?
1 year
How long before transfusion must fresh frozen plasma be thawed?
30 mins
How long after thawing must fresh frozen plasma be transfused?
Within the hour otherwise clotting factors begin to degenerate.
What is the usual dose of transfused fresh frozen plasma?
12-15 ml/kg which usually equates to about 3 bags
Do you need to crossmatch fresh frozen plasma?
No, you just need to know blood group.
What is the point of given fresh frozen plasma?
To transfuse clotting factors. Not to replace fluid!
What are the indications for transfusing fresh frozen plasma?
If the patient is bleeding AND they have abnormal clotting factor results (PT, APTT)
Reversal of warfarin anticoagulation in urgent surgery if prothrombin complex concentrate is not available.
Liver failure
Why is fresh frozen plasma becoming less used?
Because of prothrombin complex concentrate which is now what is used in a warfarin overdose.
What two components of cryoprecipitate make it a very useful product?
Fibrinogen
Factor VIII
What are the two most common clinical scenarios that require fibrinogen and hence the transfusion of cryoprecipitate?
Postpartum haemorrhage (PPH) - factors from the placenta destroy the fibrinogen Trauma
How many donors are needed to make one dose of cryoprecipitate?
10
How many donors are needed to make one bag of cryoprecipitate?
5
How many different blood groups have been described?
Over 400
What are the two most important blood group categories?
ABO
Rh
Other than ABO and Rh, can you name any other clinically important blood groups?
Duffy
Kell
Kidd
S
Which of the Rh antigens is being described when we talk about a positive or negative blood group?
Rh D
What does ABO represent in terms of blood group?
The red cell antigen. A and B code for genes that alter the H substance. O codes for silent allele that does nothing.
What is the inheritance pattern of A and B in terms of blood groups?
They are co-dominant and dominant to O
From what age do the ABO antibodies start to become expressed?
3-6 months
What type of immunoglobulin are anti-A and anti-B blood cell surface antigen antibodies?
IgM
What antibodies will someone with blood group A express?
Anti-B
What antibodies will someone with blood group B express?
Anti-A
What antibodies will someone with blood group O express?
Anti-A
Anti-B
What antibodies will someone with blood group AB express?
None
What is the frequency of blood group A people in the UK?
42%
What is the frequency of blood group B people in the UK?
8%
What is the frequency of blood group O people in the UK?
47%
What is the frequency of blood group AB people in the UK?
3%
Which ethnic group contain the highest prevalence of people with blood group B?
Asian
In determining the blood group, what is forward and reverse typing?
Forward typing - testing the cells for antigens
Reverse typing - testing the plasma for antibodies
Is the RhD antigen dominant or recessive?
Dominant - clue is in the size of the letter
What proportion of people are RhD positive?
85%
What are the two important implications of giving a RhD negative female RhD positive blood?
There are no immediate implications
The problems come with future blood transfusions and pregnancy
Will haemolytic disease of the new born affect the first born child?
Not usually. It is the second child that is affected unless the mother has had a blood transfusion of the wrong group, in which case the first born can be affected.
In haemolytic disease of the new born, is the mother RhD positive or negative?
Negative, and therefore once exposed to the RhD antigen will form antibodies against it.
Which immunoglobulin type can cross the placenta and cause haemolytic disease of the new born?
IgG antibodies against RhD
What are the severe complications of haemolytic disease of the new born?
IgG antibodies against RhD antigen cross the placenta and cause haemolysis of the fetal red cells. This can lead to hydrops fetalis and death.
How is haemolytic disease of the new born prevented?
RhD negative women are identified early in pregnancy in routine blood tests. They are then given Rh immunoglobulin (RhIg or RhoGAM) at around the 28th week which prevents them from making antibodies. After the baby is born the mother should receive another dose of RhIg within 72 hours IF the baby is found the RhD positive.
What is the purpose of the direct antiglobulin test (DAT), also known as the direct Coomb’s test and how is it done?
To detect the cause of haemolytic anaemia, to investigate a transfusion reaction, and to diagnose haemolytic disease of the new born.
The direct test looks for antibodies already stuck to the patients cell in vivo by adding antibodies against other antibodies.
What is the purpose of the indirect antiglobulin test, also known as the indirect Coomb’s test and how is it done?
To detect antibodies directed against red blood cell
antigens in the patients plasma, in preparation for a blood transfusion, or during pregnancy and at delivery.
The indirect test looks for antibodies in the plasma of the patient and cross reacts them with the cells of the donor or baby. The same antibodies (as the direct test) to the patient’s antibodies are then added.
What is the purpose of an antibody screen prior to a blood transfusion?
To see if the recipient has any atypical antibodies such as anti-M. It is done by testing plasma from the recipient against panels of red blood cells with known antigens.
Do we naturally develop antibodies against all the red cell antigens that we are lacking?
No, in all cases except for the ABO group the development of antibodies only comes post transfusion or pregnancy.
What is a crossmatch in terms of blood transfusions?
Plasma from the recipient will be mixed with
a small bit of blood from the donor bag. If there is no
reaction, then it is cross match compatible and the blood
is reserved for that patient.
Why would someone need irradiated blood as a transfusion?
If they have depressed T cell function, eg post bone marrow transplant, di George, Hodgkin lymphoma, leukaemia, AIDS, certain drugs (fludarabine)
What are the special request blood transusions available?
Irradiated CMV negative - immunocompromised Specific phenotypes (Rh and Kell) Washed Plasma depleted T antigen negative
What are the two types of transfusion reaction?
Immune
Non-immune
How can the immune transfusion reactions be subdivided?
Acute
Delayed
What is haptoglobin?
Haptoglobin binds free Hb released from erythrocytes with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen). Haptoglobulin assay is used to screen for and monitor intravascular hemolytic anemia.
What might you see on a blood film in a haemolytic anaemia or splenomegaly?
Reticulocytes - distinguishable by the small amount of DNA that will be left in the cell.
What are the main symptoms of an acute haemolytic transfusion reaction?
Chills Fever Jaundice Hypotension Tachycardia Pain in chest and lumbar region Haemoglobinuria Hyperbilirubinemia
How would you manage someone who is having an acute haemolytic transfusion reaction?
Urgent medical review (possibly ITU) Stop transfusion IV fluids Take obs Haemoflitration - red cell exchange Oxygen high flow Steroids (+/- adrenaline) Possibly antiobiotics
What are the clinical features of transfusion related acute lung injury?
Pulmonary capillary leakage leads to pulmonary oedema and acute hypoxia (without heart failure)
Occurs within 4 hours of a blood transfusion
Mortality of 30-50%
Not easily distinguished from ARDS
How long after blood transfusion does post transfusion purpura present?
5-12 days
Does post-transfusion purpura most often affect males or females?
Females
What is the underlying cause of post-transfusion purpura?
Platelet specific alloantibodies causing an immune mediated thrombocytopenia.
What are the main symptoms of post-transfusion purpura?
Bleeding
Bruising
How is post-transfusion purpura managed?
It is usually self limiting but may require IVIg. Plasmapheresis is also an option.
Important to exclude donor from further blood donations.
What is the underlying pathology of transfusion associated graft versus host disease (TA-GvHD)?
Immune reaction of donor T cells against
the recipient. The recipient is often immunodeficient.
How long after transfusion does transfusion associated graft versus host disease (TA-GvHD) usually present?
Can be anything from 4 days to 6 weeks
What are the signs and symptoms associated with transfusion associated graft versus host disease (TA-GvHD)?
Fever Skin rash Pancytopenia Liver failure Renal failure
What is the mortality rate of someone with transfusion associated graft versus host disease (TA-GvHD)?
75-90% - There is no effective treatment
How long after infusion will signs and symptoms of transfusion associated infective shock present?
During the transfusion
Usually during the transfusion of the first 100mls
What are the non-immune causes of acquired haemolytic anaemia?
Hypersplenism Infections Trauma - such as burns Lead poisoning Paroxysmal nocturnal haemoglobinuria Renal disease Liver disease
What are the clinical features of haemolysis?
Jaundice - unconjugated hyperbilirubinaemia
Anaemia
Reticulocytosis
Macrocytosis
Morphological changes - spherocytes, fragmented cells
Marrow hypertrophy and hyperplasia
What is the test used to detect haemoglobin-albumin complex?
Schumms test
Infections by which organisms do people who are iron overloaded tend to get?
Gram negative bacteria
