blood transfusion

Question 1

what is the fundamental problem of blood transfusion? 3

Answer 1

• red blood cells have antigens on their surface
• human plasma may contain antibodies to these antigens
• these can cause reactions- sometimes fatal

Question 2

describe the ABO system? 4

Answer 2

• A- A antigen, B antibodies in blood plasma
• B- B antigen, A antibodies in blood plasma
• AB- A and B antigens, no antibodies in blood plasma
• O- no antigens, A and B antibodies in blood plasma

Question 3

what are agglutinins?

Answer 3

naturally occurring pentameric IgM antibodies

Question 4

explain ABO antibodies? 6

Answer 4

• occur naturally due to cross reactivity with gut bacterial organs
• these are IgM able to fix complement and cause red cell lysis
• transfusion of ABO incompatible blood causes intravascular lysis
• shock, hypotension, tachycardia
• renal failure, loin pain
• death

Question 5

what is cross matching? 2

Answer 5

• forward grouping= mix blood- reactions show what antigens are present on the blood
• reverse grouping- mix plasma- reactions show what antibodies are present in the plasma

Question 6

explain ABO compatibility? 4

Answer 6

• Blood group AB can give blood to AB and can receive blood from AB, A, B, O
• Blood group A can give blood to A and AB, and can receive blood from A and O
• Blood group B can give blood B and AB, and can receive blood from B and O
• Blood group O can give blood to AB, A, B, O and can receive blood from O

Question 7

describe the blood group frequencies? 4

Answer 7

• O= 46% of UK
• A= 42% of UK
• B= 9% of UK
• AB= 3% of UK

Question 8

how can we read blood grouping with gel cards?

Answer 8

• If the blood is at the top of the column then there has been an agglutination reaction, if the blood is at the bottom, then there has been no reaction. The control should be negative

Question 9

what is group and screen? 3

Answer 9

• This is what the lab does when you send a sample
• Test the ABO group of the red cells
• Screen the plasma for atypical antibodies

Question 10

what are atypical antibodies? 2

Answer 10

• these arise due to sensation with foreign red blood cell antigens caused by blood transfusion or pregnancy
• atypical antibodies can cause blood transfusion reactions if the patient is transfused with incompatible blood int he future

Question 11

what is the coombs test? 3

Answer 11

• The coombs test is also known as the anti-globulin test
• It uses anti-immunoglobulin antibody to agglutinate red cells
• There are two types: direct (DAT) and indirect (IAT)

Question 12

what does the DAT tell us? 3

Answer 12

• The DAT tells us if red cells are coated with antibody
• It is positive after a transfusion reaction and in HDN
• It is also positive in autoimmune haemolytic anaemia

Question 13

what does the IAT tell us? 2

Answer 13

• The IAT is used in the lad foe testing blood group antigens
• It can tell us if a patient is positive for Rhesus (D) and other blood groups

Question 14

what is the rhesus system? 5

Answer 14

• Rh positive people cannot develop Rh antibodies ad they have the antigen
• 15% of people are Rh negative
• Rh negative people can develop antibodies if they are transfused with Rh positive blood or are pregnant with a Rh positive baby
• this is called rhesus sensitisation and the antibody generated is the IgG type
• the most important antigen is RhD

Question 15

what is rhesus D sensitisation? 5

Answer 15

• people who develop Rh antibodies cannot be given Rh positive blood
• if a mother who is negative is pregnant with a positive foetus, she may produce antibodies which can cross the placenta and harm the baby
• this is known as haemolytic disease of the new born
• can cause anaemia, jaundice and kernicterus (brain damage)

Question 16

how can we prevent haemolytic disease of the new born? 4

Answer 16

• pregnant women have the ABO + Rh blood group check at 12 weeks
• negative women receive an anti-D antibody through injection at 28 and 34 weeks to prevent sensitisation
• baby is tested at birth and if Rh positive the mother receives further anti-D until foetal cells become negative
• if already sensitised then the foetus requires monitoring via transcranial doppler and may require intra-uterine transfusions if there are signs of anaemia

Question 17

what is in a bag of donated blood? 4

Answer 17

• red blood cells
• buffy coat ( white cells and platelets)
• plasma (albumin, gamma globulins, coagulation factors)
• water, electrolytes and additives

Question 18

what is an aphaeresis machine?

Answer 18

• machine which allows us to take only one aspect of the blood like platelets or plasma

Question 19

when do we give a blood transfusion? 4

Answer 19

• Severe acute blood loss- trauma, HI blood loss, obstetric blood loss
• Elective surgery associated with significant blood loss
• Medical transfusions- cancer/ renal failure
• Anaemia- symptomatic anaemia

Question 20

what are the different types of blood transfusion? 4

Answer 20

• Blood components (red cells, platelets, fresh frozen plasma, cryoprecipitate (fibrinogen))
• Plasma derivatives (immunoglobulin, coagulation factors, albumin)
• Cell salvage (rarely done during operations)
• Autologous transfusion (taken from patient and given back later- rarely done)

Question 21

describe blood availability? 3

Answer 21

• O negative is emergency blood and can be delivered in 5 mins
• group compatible (same as patient) takes 10-15 mins
• fully screened and cross matched (45 mins but maybe hours)

Question 22

describe some blood transfusion reactions? 7

Answer 22

• Major ABO incompatibilities- acute renal failure, death
• Febrile non-haemolytic reactions
• Fluid overload
• Anaphylaxis or severe allergic reactions
• Minor allergic reactions
• Delayed transfusion reactions
• Transfusion related acute lung injury

Question 23

name some physiological hazards of blood transfusion and how they are resolved?

Answer 23

• fluid overload when the blood doesn’t infuse quickly, can cause pulmonary oedema or circulatory overload
• diuretic should resolve this
• iron overload (haemosiderosis) iron is deposited in tissues
• iron chelation should resolve this