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Year 3 Clinical > Blood Tranfusions > Flashcards

Blood Tranfusions Flashcards

1
Q

Types of blood components?

A
  1. Red cells
  2. Platelets
  3. Fresh frozen plasma
  4. Cryoprecipitate
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2
Q

How are blood components obtained?

A

Centrifuging anti-coagulated blood, separating it into red cells (most dense), buffy coat (wbcs and platelets) and plasma (least dense)

From 1 blood donation:
• 1 unit of red cells
• 1 unit of plasma - if frozen within 8 hrs, it is fresh frozen plasma
• 1/4 of an adult therapeutic dose of platelets

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3
Q

Types of blood products?

A
  1. Human albumin
  2. IV Ig
  3. Human normal Ig
  4. Specific Igs, e.g: tetanus, hep B, varicella zoster, rabies)
  5. Anti-D Ig
  6. Prothrombin complex concentrates
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4
Q

How are blood products obtained?

A

Subject human plasma to a manufacturing process to obtain plasma fractions, e.g: albumin, Ig, coagulation components

For a batch of one of these products, the starting material may consist of plasma from up to 20,000 donations; i.e: when a patient receives blood products, they are EXPOSED TO MANY DONORS

NOTE - cannot use plasma from UK blood donors for the manufacture of blood products, due to the risk disseminating CJD

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5
Q

How can a dull adult therapeutic dose of platelets be retrieved?

A

From 4 donors (each donating a 1/4 of the therapeutic dose)

From a single donor, using a cell separator machine; these platelets are labelled platelets - apheresis

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6
Q

Basic criteria for blood donors?

A

Volunteers

Healthy

Able to spare 465ml of blood:
• Minimum weight of 50kg
• Hb of 13.5 g/dL (males) or 12.5 g/dL (females) at least

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7
Q

How to ensure safety of the raw material?

A

Exclude infective risk

Exclude risk of transmitting disease, e.g: malignancy, neuro conditions of uncertain origin (like MS)

Donor is encourage the centre if they become unwell within 2 weeks of donating, in order to recall the blood

Blood is tested:
• HIV 1 + 2 (Ab + PCR)
• HCV (Ab + PCR)
• HBV (antigen + PCR)
• Syphilis (antibody)
• HTLV I + II (antibody)
• HEV (PCR)
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8
Q

Steps in collecting blood donation?

A
  1. Bleed the donor - collected into a primary bag containing anti-coagulant
  2. Centrifuge the bag, to separate the red cells, buffy layer and plasma
  3. Express the components by snapping the tubing; plasma is expressed into the top bag, red cells into the bottom bag and the buffy coat is left in the primary bag
  4. Leucodeplete the red cells and add nutrient solution, which provides nutrients and maintains osmotic equilibrium to limit red cell damage during the storage period of 35 days.

NOTE - the buffy coat from 4 donations can be spun, to separate platelets from wbcs

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9
Q

Rules regarding the storage and use of red cell concentrate?

A

Must be stored at 4 degrees C +/- 2 degrees

SHELF LIFE of 35 DAYS

If removed from controlled storage for >30 mins, must either transfuse or discard

Must be transfused within 4 hours of leaving controlled storage

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10
Q

Rules regarding the storage and use of platelets?

A

Stored at 22 degrees C (room temp) with continual agitation, to promote gas exchange; MUST NOT BE IN A FRIDGE

Shelf life of 7 days, if bacterial monitoring system is employed

Transfuse within 1 hour

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11
Q

Rules regarding the storage and use of fresh frozen plasma?

A

Stored at -30 degrees C for up to 3 years

Thawed prior to transfusion and transfused within 4 hours

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12
Q

Major blood groups?

A
  1. ABO
  2. Rh(D)
  3. Others, e.g: Kell, Lewis, Duffy, Kidd, etc

NOTE - there are 33 recognised blood group systems

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13
Q

Normal shape of a rbc?

A

Bi-concave

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14
Q

4 ABO groups?

A

Group A - rbcs have A antigen (population frequency of 42%)

Group B - rbcs have B antigen (population frequency of 8%)

Group AB - rbcs have A and B antigens (population frequency of 3%)

Group O - rbcs do not have A or B antigens (population frequency of 47%)

NOTE -

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15
Q

How is the generation of auto-antibodies to environmental bacteria related to blood group?

A

some environmental bacteria, esp gut colonisers, carry antigens that look like A or B antigens; by ~6 months of age, the gut is colonised and the immune system responds to non-self antigens

A patient with blood group O develops antibodies to A and B antigen (anti-A and anti-B antibody)

A patient with blood group A develops antibodies to B antigen (anti-B antibody)

A patient with blood group B develops antibodies to A antigen (anti-A antibody)

A patient with blood group AB develops no antibodies, as neither are foreign

NOTE - most ABO-antibodies are primarily IgM and they agglutinate target red cells

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16
Q

Term for patients with blood group O?

A

Universal donor

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17
Q

Term for patients with blood group AB?

A

Universal recipient

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18
Q

Genes determining ABO blood group?

A

Located on chromosome 9

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19
Q

Inheritance of ABO blood group?

A 
Mendelian inheritance:
• A and B genes - code for specific transferase enzymes that add a sugar residue to a precursor H substance, on the red cell membrane
• O gene is silent
• A and B are dominant over O
• A and B are co-dominant

NOTE - to have O grouping, must inherit an O allele from both mother and father, although they have any ABO group between them, except AB

If AB blood group, neither mother nor father can be group O

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20
Q

Genes determining Rh(D) +ve or -ve?

A

Located on chromosome 1; there are 2 alleles (D and d)

NOTE - if a patient is Rh(D) +ve, they have Rh(D) protein on their red cells; if -ve, this is absent

Inheritance is Mendelian

Possible genotypes:
• DD - Rh(D) +ve
• Dd - Rh(D) +ve
• dd - Rh(D) -ve

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21
Q

Antibodies against Rh(D)?

A

Most people do not have antibodies against Rh(D), as there are no environmental bacterial antigens that have a resemblance

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22
Q

Situations where antibodies can develop against Rh(D)?

A

If Rh(D) -ve and exposed to red cells that are Rh(D) +ve:
• Pregnancy with a Rh(D) +ve foetus
• Transfusion with Rh(D) +ve red cells

In these cases, there is a significant risk that the patient will develop anti-Rh(D) antibody, AKA anti-D

NOTE - this becomes a problem if the 2nd pregnancy or transfusion has Rh(D) +ve red cells

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23
Q

Why can all recipients not just receive O group red cells?

A

Limitations on availability of O blood

NOTE - universal donors are not guaranteed to be compatible for every patient, due to irregular red cell antibodies

Should determine Rh(D) status

24
Q

How is blood group determined?

A

Based on the agglutination phenomenon
• Addition of anti-A antibody to group A red cells causes red cell agglutination
• Addition of anti-B antibody to group B red cells causes red cell agglutination
• Addition of anti-A antibody to group B or group O red cells produces no effect

25
Q

What is this patient’s blood group?

A

Patient’s red cells + Anti - A = no agglutination
Patient’s red cells + Anti - B = no
Patient’s red cells + Anti - A,B = no

Patient’s plasma + A red cells = yes
Patient’s plasma + B red cells = yes
Patient’s red cells + Anti - D = yes

Blood group - O Rh(D) +ve

NOTE - the typing of plasma confirms the results obtained from typing the red cells

26
Q

What is this patient’s blood group?

A

Patient’s red cells + Anti - A = no
Patient’s red cells + Anti - B = no
Patient’s red cells + Anti - A,B = no

Patient’s plasma + A red cells = yes
Patient’s plasma + B red cells = yes
Patient’s red cells + Anti - D = yes

27
Q

Why are other antibodies in the blood significant?

A

Significant when red cells carrying one of the antigens is given to a recipient with the corresponding antibody

NOTE - if a patient has an antibody to one or more of the antigens, i.e: irregular antibodies, then the red cells for transfusion must be -ve for that antigen

28
Q

Cautions when taking a blood sample for cross-match?

A

Must ask patient to confirm name and DoB; check their wristband

Take sample

Without leaving bedside, ask for another confirmation of name and DoB and write details on tube and then the blood tranfusion request form

29
Q

Steps in compatibility testing for red cell transfusion?

A
  1. Check patient’s previous transfusion history
  2. Centrifuge sample to separate red cells, buffy layer and plasma
  3. Determine ABO group and Rh(D)
  4. Screen patient’s plasma for irregular red cell antibodies

NOTE - automated blood grouping is common; the agglutinated red cells remain trapped at the top of the column

30
Q

How do irregular red cells antibodies develop?

A

Not naturally occurring, unlike anti-A and anti-B

Develop following exposure to red cells:
• Previous transfusion
• Previous pregnancy

31
Q

Most common irregular red cell antibodies?

A

Anti-D

Anti-K

Anti-c

Anti-E

32
Q

How to screen for irregular red cell antibodies?

A

Coomb’s test:
• Direct anti-globulin test (DAGT) - check if their antibody bound to the red cells in the post-transfusion sample
• INDIRECT anti-globulin test - test method for the detection of red cell allo-antibodies; this is used for detection of irregular red cell antibodies

Relies on agglutination phenomenon

Uses group O red cells (to exclude any influence of anti-A or anti-B antibodies) from 3 donors, whose red cells have been selected so that, between them, they carry all the clinically significant red cell antigens

33
Q

What happens to compatible selected units for a patient?

A

Issued to the appropriate blood fridge

If not required, they are collected 24 hours later and can be returned to the blood bank to be available for cross-match for another patient

34
Q

What is Group & Save?

A

ABO group, Rh(D) type and irregular antibody screen - used for operations in which there is a <30% chance of requiring red cells; thus, if blood is required, it can be provided within 10 minutes of a request

35
Q

Indications for red cell transfusion?

A 
1. Anaemia - consider the need (symptoms vs Hb), e.g: low Hb with:
• Reduced exercise capacity
• Coincidental medical/surgical issues
• Heart/lung issues
• Anaemia symptoms
  1. Acute blood loss (if unpredictable and potentially unlimited)
36
Q

Approach to acute blood loss?

A
  1. Arrest bleeding
  2. Gain IV access
  3. Samples for cross-matching, and other tests
  4. Restore and maintain blood volume - N saline, albumin, gelofusin
  5. ABO and Rh(D), Ab screen and cross-match - 1 hour
    • Type specific (ABO and Rh(D) - immediate spin cross-match takes 10- 20 minutes
    • Emergency Group O Rh(D) negative blood - immediately available but not compatible for every patient
  6. Aim at least to maintain normal HR, BP, consciousness, urine output >30 ml/hr, Hb > 100 g/L

NOTE - if blood losses are replaced with fluid other than blood, Hb conc. will fall (haemodilution), so must make plans to obtain blood components

37
Q

Matching for platelet transfusions?

A

No cross-match required but take account of donor and recipient ABO and Rh(D) groups

38
Q

Indications for platelet transfusion?

A

Low platelet count - how low? (not an indication itself)

Patient age

Symptoms of bleeding

Direction of change of platelet count

Platelet kinetics

Underlying infection/ fever

Concomitant anaemia

Concomitant drugs

Requirement for / recovery from surgery

Congenital platelet functional defects

Acquired platelet functional defects, e.g: myeloma, uraemi

39
Q

Indications for fresh frozen plasma?

A

Bleeding or surgery in liver disease with impaired coagulation

Coagulopathy following massive transfusion

Disseminated intravascular coagulation (DIC)

40
Q

Why do immediate haemolytic transfusion reactions occur?

A

Some of the irregular antibodies can cause this, although the main reason is transfusion of ABO incompatible red cells

IgM antibodies initiate full activation of the complement cascade, with the formation of the membrane-attack complex, which ruptures the transfused red cells

Thromboembolastic material from haemolysed red cells leads to DIC

Activated factor XII activates the kinin system, leading to formation of bradykinin:
• Arteriolar dilatation
• Increased vascular permeability
Leads to hypotension and release of catecholamines, which vasoconstricts vessels in the kidneys and other organs

NOTE - there are 3 linked systems (complement, coagulation and kinin systems)

41
Q

Types of complement involved with immediate haemolytic transfusion reactions?

A

Release of C3a and C5a (powerful anaphylotoxins); there is increased vascular permeability and dilatation of blood vessels

42
Q

Symptoms and signs of acute haemolytic transfusion reactions?

A

Can occur with transfusion of only 1ml

Release of serotonin and histamine:
• Pyrexia, rigors
• Dizziness
• Tachycardia, tachypnoea, hypotension
• Pallor, sweating
• Headaches, chest or lumbar pain
• Local pain at infusion site
• Cyanosis

Renal vasoconstriction and renal failure

DIC

OFTEN FATAL

43
Q

Mx of acute haemolytic transfusion reaction?

A

Stop transfusion but DO NOT REMOVE THE CANNULA, as their crashing BP will make it difficult to insert another

Start IV fluids to maintain BP and urine output

Obtain blood samples for transfusion lab

44
Q

What is haptoglobin?

A

Binds free Hb and is then rapidly removed from the circulation

Level likely to be low after ABO incompatible transfusion

45
Q

Presentation of delayed haemolytic transfusion reactions?

A

Haemolysis usually 5-10 days after transfusion

Variable PC - similar, but less acute than, an immediate reactions

There is an unexplained fall in Hb, appearance of jaundice, renal failure or biochemical features of a reactions

Detection of +ve DAGT or irregular antibodies in post-transfusion blood samples

46
Q

Lab features of delayed haemolytic transfusion reactions?

A

Anaemia

Spherocytic red cells on blood film

Elevated bilirubin and LDH

+ve DAGT and/or appearance of red cell allo-antibody

+/- a degree of renal failure

47
Q

Mechanism of delayed haemolytic transfusion reactions?

A
  1. Patient mounts a delayed
    immune response to foreign
    red cells
  2. Antibody is produced,
    and attaches to the
    foreign antigens
3. Ab-Ag reaction results
in extravascular
(spleen) destruction
of transfused red
cells

NOTE - the addition of anti-human globulin to these sensitised red cells results in their agglutination, i.e: a +ve DAGT

48
Q

What is febrile non-haemolytic transfusion reactions?

A

Fairly common but not usually life-threatening but difficult to differentiate from more serious reactions

Tend to occur once a fair amount of implicated component has been transfused and are more common in patients who are often transfused

49
Q

Symptoms and signs of febrile non-haemolytic transfusion reactions?

A

Rapid temp rise, rigors

50
Q

Ix for febrile non-haemolytic transfusion reactions?

A

HLA antibodies may be detectable

No evidence of red cell incompatibility

51
Q

Prevention of febrile non-haemolytic transfusion reactions?

A

Anti-pyretics

Leucodepleted blood components

52
Q

What is an urticarial reactions?

A

Mast cell-IgE response to infused plasma proteins

Rash/weals within a few minutes of starting transfusion

53
Q

Mx of an urticarial reaction?

A

Slow the transfusion

Consider anti-histamines

54
Q

Why may circulatory overload occur with a transfusion?

A

Patients who already have circulatory impairment can develop pulmonary oedema

Elderly patients and those with CCF are at high risk

55
Q

Prevention of circulatory overload?

A

Reduce transfusion rate (remember 4 hour time limit though)

56
Q

Signs of bacterial infection with transfusion?

A

Fever, rigors, vomiting, immediate collapse, shock, DIC (similar to ITHT reaction)

Potentially fatal

57
Q

Significant bacteria?

A

Red cells - pseudomonas, Yersinia

Platelets - Staph, Strep, Serratia, Salmonellae

Year 3 Clinical (100 decks)

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