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review haem > Haem: Blood Transfusions 1 > Flashcards

Haem: Blood Transfusions 1 Flashcards

1
Q

What proportion of population are RhD negative?

A

15%

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2
Q

What type of antibodies are anti-RhD?

A

IgG

Therefore can cross the placenta

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3
Q

Describe how the consequences ABO incompatibility are different to rhesus incompatibility.

A
  • ABO - immediated haemolytic transfusion reaction (can be fatal)
  • Rhesus - delayed haemolytic transfusion reaction
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4
Q

Why does rhesus incompatibility cause delayed haemolysis?

A

Because IgG-binding leads to extravascular haemolysis

IgG activates complement less that IgM

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5
Q

List some other antigens that can lead to transfusion reactions.

A
  • Rhesus C, c, E, C
  • Kell (K), Duffy and Kidd (particularly important for delayed transfusion reactions)
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6
Q

What is a dangerous consequences of rhesus incompatibility in a pregnant woman?

A

Haemolytic disease of the newborn

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7
Q

How is the patient’s blood group tested?

A
  • Anti-A, anti-B and anti-D reagents are mixed with the patient’s red blood cells
  • A positive result means that the red cells will float to the top of the vial (agglutination)

Takes 10 minutes - done before every transfusion

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8
Q

How can the types of red blood cell antibodies in the patient’s serum be identified?

A

Known A and B group red blood cells are mixed with the patient’s plasma (which contains IgM antibodies)

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9
Q

Describe how the antibody screen of a patient’s plasma works.

A
  • Conducted using the indirect antiglobulin test (IAT)
  • 2 or 3 reagent red blood cells are used which contain all the important red cell antigens
  • The patient’s serum is incubated with these screening cells
  • Anti-human immunoglobulin is added to the solution which allows briding of red cells that are coated with IgG
  • This results in the formation of a visible clump
  • This is a group and screen
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10
Q

What labels are included on issued blood?

A

ABO and RhD status

Other Rh antigens and K

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11
Q

Which patient group should receive K negative blood?

A

Women of childbearing potential

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12
Q

What is a full crossmatch?

A
  • Uses indirect antiglobulin test
  • Patients plasma is incubated with DONOR red cells at 37 degrees for 30-40 mins
  • Anti-human immunoglobulin is added to allow cross-linking of antibodies
  • Formation of a clump would suggest that antibodies against donor red cell antigens are present in the patient’s plasma

Not suitable in emergencies due to because it take 40 minutes

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13
Q

What is an immediate spin?

A
  • Incubate patient’s plasma and donor red cells for 5 mins and spin
  • This will only detect ABO incompatibility
  • Used in emergency situations
  • IgM anti-A or anti-B will bind to donor RBCs, fix complement and lyse cells
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14
Q

What is an electronic crossmatch?

A
  • Also called electronic issue (EI)
  • Compatibility is determined by an IT system without physical testing of donor cells against plasma

How it is done now in modern era - quick, requires fewer staff and allows better stock management

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15
Q

How long do red cells survive in storage?

A

35 days in 4 degrees

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16
Q

How soon after leaving storage do red cells need to be transfused?

A

4 hours

NOTE: red cells can be returned to the fridge within 30 mins of leaving storage

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17
Q

Describe how platelets are cross-matched.

A

They do NOT need cross-matching because the antigens are weakly expressed

18
Q

Which antigens are important when considering fresh frozen plasma plasma transfusion?

A

Only ABO

19
Q

If group O blood is given to A, B or AB patients, what precaution should you take?

A

Do not use high titre blood (i.e. blood that does not contains high levels of anti-A and anti-B antibodies)

20
Q

What is the universal donor for:

  1. Red blood cells
  2. Plasma
A
  1. Red blood cells = O negative
  2. Plasma = AB (contains no anti-A or anti-B antibodies)
21
Q

Why do platelets have a shorter shelf-life than red blood cells?

A

They are stored at room temperature so they are more likely to get contaminated by bacteria

22
Q

What should you do if a patient receiving a platelet transfusion develops a fever?

A
  • Stop the platelets and take blood cultures
  • Platelets should be sent back to the lab for microbiological testing
23
Q

If a patient develops a reaction to a plasma transfusion, what is the most likely cause?

A

Allergic reactions

NOTE: plasma is frozen so it is unlikely to get contaminated by bacteria

24
Q

List some indications for RBC transfusion.

A
  • Major blood loss - if >30% blood lost
  • Peri-operative care - if Hb <70g/dL
  • Post-chemotherapy - if Hb <80g/dL
  • Symptomatic anaemia - ischaemic heart disease, breathless
25
Q

By how much would 1 unit of RBC increase the haemoglobin leel in a 70kg patient?

A

10 g/L

26
Q

If a group and screen is performed and no antibodies are present, is a crossmatch necessary?

A

No

27
Q

List some methods of transfusing your own blood.

A
  • Pre-operative autologous deposit (not available in the UK)
  • Intra-operative cell salvage (blood is collected during surgery, centrifuged, filtered and reinfused)
  • Post-operative cell salvage (blood that is lost post-operative is collected via a wound drain, filtered and re-infusd - usually for orthopaedic operations)

NOTE: all coagulation factors and platelets are removed in cell salvage

28
Q

Which patient groups would cell salvage be used for?

A
  • Patients with rare blood groups
  • Jehovah’s witnesses
29
Q

Which patient groups require CMV-negative blood?

A
  • For intra-uterine and neonatal transfusions
  • Elective transfusion in pregnancy
30
Q

Which patients require irradiated blood and why?

A

Highly immunosuppressed patients

  • These patients cannot destroy donor lymphocytes and the presence of lymphocytes in donated blood can cause transfusion associated graft-versus-host disease
31
Q

Which patients require washed blood?

A
  • Patients who have severe allergic reactions to donors’ plasma proteins
  • This takes 4 hours so must be requested in advance

NOTE: IgA deficient patients are more likely to need washed blood

32
Q

List some indications for platelet transfusions.

A
  • Massive transfusion - aim for >75 x 10^9/L
  • Prevent bleeding (post-chemotherapy) - if <10 x 10^9/L
  • Prevent bleeding (surgery) - if <5 x 10^9/L
  • Platelet dysfunction or immune cause - only if actively bleeding
33
Q

List some contraindications for platelet transfusion.

A
  • Heparin-induced thrombocytopaenia
  • TTP
34
Q

By what level will 1 unit of platelets increase the platelet count in a 70 kg adult?

A

30-40 x 10^9/L

35
Q

List some indications for FFP transfusion.

A
  • Massive transfusion
  • DIC (if bleeding or invasive procedure)
  • Liver disease
36
Q

What does FFP contain?

A

All the coagulation factors

37
Q

What is the adult dose of FFP?

A

15 mL/kg

4 units

38
Q

How many mLs is 1 unit of FFP?

A

250mL

Patients usually given 4 units

39
Q

What is the best option for the reversal of warfarin?

A

Prothrombin complex concentrate (contains 2, 7, 9 and 10)

40
Q

What does cryoprecipitate contain?

A
  • Fibrinogen
  • FVIII and vWF
  • Fibronectin
  • FXIII
  • Platelet microparticles
  • IgA
  • Albumin
41
Q

What is the most common blood type?

A

O positive (1/3 of donors)

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