Blood Transfusion Flashcards
What is the requirement for blood donation?
Hb 135 g/L men
Hb 125 g/L women
Weight 50kg
Aged 17-65
How is donated blood processed and tested?
Bag of whole blood centrifuged to separate into component parts
Samples undergo microbial testing; HIV, hep B + C, hep E, HTLV, syphilis
How are the components of donated blood stored?
Red cells; 4 degrees for 35 days
FFP; -30 for 3 years
Platelets; 22 degrees for 7 days with agitation
What blood components are available from donated blood?
Red cells
FFP
Platelets
Cryoprecipitate
What blood products are available from donated blood?
Anti-D Ig
Prothrombin complex - used in warfarin overdose
What are the most important antigens to match up when transfusing blood?
ABO
Rh D
On what chromosome is the ABO gene located?
9
What do A and B genes code for?
Transferases which modify precursors called “H substance” on the red cell membrane
What is the most common blood group?
O
Then A
Then B
Then AB
What is the genotype of group O and what antibodies are present in the plasma?
OO
Anti A and anti B
What is the genotype of group A and what antibodies are present in the plasma?
AA or AO
Anti-B
What is the genotype of group B and what antibodies are present in the plasma?
BB or BO
Anti-A
What is the genotype of group AB and what antibodies are present in the plasma?
AB
Neither
What is landsteiner’s law?
When an individual lacks the A or B antigen, the corresponding antibody is produced in their plasma
What % of the population are RhD positive?
85%
Is rhesus status autosomal dominant or recessive?
Dominant for positive rhesus status
What can anti-D antibody reaction cause?
Transfusion reaction
Haemolytic disease of the foetus and newborn
What are the aims of pre-transfusion testing?
To identify ABO and RhD groups
To identify presence of clinically significant red cell antibodies
How can ABO be grouped?
Use reagents with known antibody specificity to identify antigens present on red cells
Use red cells with known antigen specificity to identify antibodies present in plasma
What is the purpose of testing patient’s red cells with anti-A, anti-B and anti-D antisera?
Identify antigens on red cells
IgM reagents; direct agglutination
What is the purpose of testing patients plasma against reagent red cells of group A and B?
Identify antibodies in the plasma
How are antibodies screened for in the blood?
Tests patient’s plasma against several reagent red cells which express a known range of antigens
Identifies antibodies in the plasma
Use the indirect anti-globulin test (addition of anti-human globulin to plasma/ red cell suspension facilitates red cell agglutination)
What does agglutination suggest in an indirect coombs test?
Presence of an antibody
What is the final test done before a blood transfusion occurs?
Cross match to check the donor cells and compatible with patient plasma
What does agglutination suggest in a crossmatch?
Donor cells are incompatible with patient plasma
What are indications for red cell transfusion?
Symptomatic anaemia Hb <70 g/L (80g/L if cardiac disease)
Major bleeding
What are the indications for a platelet transfusion?
Prophylaxis in patients with bone marrow failure and very low platelet counts
Treatment of bleeding in thrombocytopenic patients
Prophylaxis prior to surgery/ procedure in thrombocytopenic patient
Always consider cause before transfusion
What are the indications for an FFP transfusion?
Treatment of bleeding in patient with coagulopathy (PT ratio >1.5)
Prophylaxis prior to surgery or procedure in patient with coagulopathy (PR >1.5)
Management of massive haemorrhage
Transfuse early in trauma
NOT in the absence of bleeding/ planned procedure
How should a patient be monitored during a transfusion?
Observations before blood is commenced
Observations at 15 mins
Observations within 60 mins of completion
