3.5 Transfusion

Question 1

Blood donation is voluntary and unpaid, and the donor must be well (satisfying age and weight requirement) with a Hb count ____________ (females) or ___________
• Must complete a questionnaire to screen out high risk donors (keep blood safe for patients and prevent harm to donors e.g. heart/renal failure)
•__________ of blood is drawn each time (replaced by the body in about 3 days), with an interval of 12 weeks between donations
• Donors are advised to avoid lifting or carrying heavy items for at least 12 hours and to refrain from strenuous or athletic activities for 24 hours (reduces bruising at venepuncture site and risk of fainting from _______________)

Answer 1

> 12.5g/dL;

> 13.0g/dL (males):

350 – 450mL;

postural hypotension

Question 2

There are certain groups of people who are excluded from being a donor, including:
• Major medical diseases (e.g. strokes, AMI, chronic kidney/liver failure)
• Pregnancy (includes post-partum/breastfeeding)
• IV drug users/certain medications/vaccinations
• Overseas travel/deferral criteria (Zika, malaria, variant Creutzfeldt-Jakob disease, West Nile virus, dengue)
• Lived in UK between _____________ or in France since 1980 (risk of _______)
• Infections (HIV, syphilis, dengue, hepatitis)
• High risk behaviours (tattoos, sexual practices)

Answer 2

1980 and 1996;

vCJD

Question 3

The HSA tests all donated blood for the following blood-borne pathogens to prevent unintentional transmission to recipients:
• HIV 1 and 2*
• Hepatitis B and C viruses*
• Syphilis (______________)
• Malaria (Plasmodium; for selected at-risk units)
• Cytomegalovirus (CMV)
• Bacterial contamination in all platelet concentrates (prior to release)
*______________________ is performed for hepatitis B, C and HIV as the usual virology testing may not capture infections within the window period.

Answer 3

Treponema pallidum;

Nucleic acid amplification testing (NAAT)

Question 4

PROCESSING OF BLOOD
1 unit of whole blood (450mL) is collected into a bag containing anticoagulant, then split by centrifuging the entire bag so _____ settle at bottom, _______ in middle and _________ at top:
• Different layers are squeezed into different satellite bags for transfusions (less wastage as 1 unit of whole blood can benefit more than 1 patient)
• Leucodepletion of blood may help reduce the risks of _________________, platelet refractoriness, ___________ transmissions, bacterial contamination and transfusion-associated GVHD

1) Collection of 1 unit (1 pint/450mL) of whole blood into a bag containing _______________
2) Weighing, filtering and centrifugation of blood at the processing centre (separates blood into RBCs (bottom), platelets (middle) and plasma (top))
3) Presser separates out the constitutes of blood (e.g. platelets and plasma from RBCs) into separate packs (sealed and detached from each other)
4) Stored under optimal conditions or undergo further processing (e.g. making ________ from fresh frozen plasma)
5) ____________ of blood pack at bedside (using special filter) ( WBCs have no therapeutic role and may cause adverse reactions
6) Transfusion into patient

Answer 4

RBCs;
platelets;
plasma;

febrile non-haemolytic transfusion reactions;

CMV and various CJD;

anticoagulant;

cryoprecipitate;

Leucodepletion

Question 5

packed red cells

• collection
• shell life
• storage

Answer 5

• 1 donor
• 5 weeks
• 4°C

Question 6

Platelets

• collection
• shell life
• storage

Answer 6

• 4 donors (standard adult dose/ 1 donor (apheresis)
• 5 days
• 22°C (with constant agitation

Question 7

fresh frozen plasma

• collection
• shell life
• storage

Answer 7

• 1 donor
• 2 years
• -30°C (within 6 hours of donation)

Question 8

PACKED RED CELLS
1 unit of packed red cells (concentrated as fluid plasma is removed) is obtained from 1 donor:
• Given through a ‘blood giving set’ which has a filter to remove ____________
• Leukocyte filter is used in some patient groups (e.g. haematological patients receiving treatment for ______________) to remove WBCs and reduce risk of transfusion-associated reactions
• Rarely need frozen red cells for rare blood groups (as frozen RBCs have poor recovery upon thawing)

Answer 8

clumps/debris;

leukaemia or BM transplant;

Question 9

PLATELETS
1 pool of platelets is made from 4 donors (at standard adult dose) or from 1 donor (via apheresis using the cell separator machine):
• Only possess a shelf life of _________, so the risk of bacterial contamination is higher than other products kept at cooler temperatures
• May contain some RBCs in the bag, which may cause _______________

Answer 9

5 days;

RhD sensitisation

Question 10

FRESH FROZEN PLASMA (FFP)
1 unit (300mL) of fresh frozen plasma (FFP) is obtained from 1 donor:
• Stored and frozen within 6 hours (to preserve the coagulation factors); must be thawed for 20 – 30 minutes before use:
o Thawing process cannot be sped up via water bath as proteins are denatured under high temperatures
o Must be given as soon as possible and ideally within 1 hour of thawing as coagulation factors degenerate at room temperature
• Dose is usually _____________ (about 3 units used for an adult)

Answer 10

12 – 15mL/kg

Question 11

Cryoprecipitate is made by thawing FFP at 4 - 8°C, centrifuging it then collecting the precipitate (containing _____________):
• Stored at -30°C for up to 2 years (same as FFP)
• Standard dose (made of 2 units) is made from 10 donors (5 donors give 1 unit)

Answer 11

fibrinogen and factor VIII

Question 12

Plasma can also be fractionated to make different blood products as it contains a large variety of proteins, including albumin, immunoglobulins, and clotting proteins:

Albumin (60% of total plasma proteins)
- For patients with burns and plasma exchanges, and for certain severe liver and kidney conditions

Factors VIII and IX (heat treated to inactivate viruses)
- For haemophilia A and B respectively, von Willebrand’s disease (factor VIII)

Immunoglobulins (given _________)

• IM (specific): for ___________________
• IM (normal globulins): for conditions like Hep A
• IV: autoimmune conditions like________________

Answer 12

IM or IV;

tetanus, Rhesus disease (anti-D Ig) and rabies;

idiopathic thrombocytopenic purpura (ITP) or autoimmune haemolytic anaemia (AIHA)

Question 13

There are more than 300 blood group antigens on RBC surface (only a minority are important in causing significant transfusion reactions):
• ABO system: most important (mistakes in transfusion may cause death)
• Rhesus system: next most important system consisting of _______________
o All Chinese people are ________________ (compared to 85% of Caucasians)
o Prevent Rh D negative females of child-bearing age from getting exposed to Rh D positive blood → causes acute haemolytic transfusion reactions and haemolytic diseases of the foetus and newborn (HDFN)
• Kell, Duffy (Fya, Fyb), Kidd (Jka, Jkb), MNS and Diego systems are also important
• Many other blood group systems exist but are mostly clinically insignificant

Answer 13

C, c, D, E, e antigens;

Rh D positive

Question 14

The positive or negative sign after the typical blood group (e.g. A+ or A-) refers to the presence of Rh D antigen:
• Rh D is the most important antigen amongst those part of the Rhesus system:
o ______________ codes for Rh D antigen on RBC membrane
o ___________ codes for no antigen
• <1% of Singaporeans are Rh D negative (6% of Singaporean Indians are Rh D negative) compared to 15% of people in the UK
• Must give _______________ to a Rh D positive woman of childbearing age to prevent the formation of anti-D antibodies which leads to future HDFN

Answer 14

Dominant D allele;

Recessive d allele

Rh D positive blood

Question 15

ABO antibodies (anti-A, anti-B)

• Naturally occurring from birth
• ___________ which fully activate the complement cascade to cause RBC haemolysis → Ab-Ag interaction often leads to fatality

Non-ABO antibodies (e.g. anti-D)

• Only formed after exposure via _____________________ (if foetal blood expresses father’s antigen that mother does not possess) → allo-antibodies*
• _____ which does not fully trigger the complement cascade → not potentially fatal (for the mother; could still be serious for the foetus in HDFN)
• The formation of allo-antibodies could be problematic if the patient is transfusion-dependent (e.g. for thalassaemia major, sickle cell anaemia).

Answer 15

IgM (complete antibodies);

transfusions of incompatible blood or pregnancy;

IgG

Question 16

A patient’s blood sample contains both plasma and RBCs, and the blood transfusion lab then performs grouping and an antibody screen before compatible blood units are selected and crossmatched (GXM):

• Grouping: Patient sample is tested for ______________ blood groups (confirms the patient’s main blood group types)
• Antibody Screen: Patient plasma sample is screened for _______________ which may cause transfusion reactions (tested against a panel of RBCs containing clinically important blood groups most often seen in practice)
• Selection: Blood units which are ABO and RhD compatible and also negative for any blood group ______________ detected are selected (prevent delayed haemolytic transfusion reactions)
• Crossmatching: Patient serum and donor RBCs from selected unit are crossmatched to ensure no reaction before issuing the actual blood unit to the patient for transfusion (if reaction occurs, unit is not compatible)

Answer 16

ABO and RhD;

RBC antibodies;

allo-antibodies

Question 17

How to test for Anti-A and Anti-B antibodies (IgM)?

Answer 17

Laboratory mixing test (visual agglutination)

Question 18

How to test for Rh antibodies (IgG)?

Answer 18

• Direct antiglobulin test (DAT)/Coomb’s test: for Ab on RBC surface (e.g. AIHA, post-incompatible transfusion)
• Indirect antiglobulin test (IAT): for Ab in plasma

Question 19

PACKED RED CELLS
The use of packed red cells must be carefully balanced between the benefits and risks (often used only when there are no safer alternatives available):
• Doctor’s decision must take into account the patient factors, comorbidities and prior clinical condition
• Massive haemorrhage (e.g. trauma, operative, postpartum): plain fluids are insufficient, and RBCs must be given
• Symptomatic anaemia (e.g. secondary to iron/B12/folate deficiency presenting with angina, dyspnoea): _______________ is insufficient

Answer 19

supplementing deficient vitamin

Question 20

Platelets are mostly given to haematology patients with _____________________, those with ________________ with bleeding and those with __________________ with bleeding:
• Can also be given to patients with massive bleeding due to trauma or DIC
• Also transfused to patients with a very low platelet count, or on anti-platelet drugs requiring urgent surgery (e.g. cardiac bypass)
• 1 pool of platelets (from 4 donors) is usually sufficient for adults, while dosing is done according to body weight for children

Answer 20

bone marrow failure (platelets < 10 x 109/L);

dengue haemorrhagic fever (DHF);

idiopathic thrombocytopenic purpura (ITP);

Question 21

FFP is indicated in patients who are bleeding with an abnormal coagulation profile (e.g. DIC):
• _____________ should be the first line of treatment for the reversal of warfarin (anticoagulant) for patients requiring urgent surgery:
o FFP is indicated when PCC is unavailable or contraindicated
• FFP also indicated in other conditions like _____________ (patient’s plasma is removed and replaced with FFP)

Answer 21

Prothrombin complex concentrate (PCC);

plasmapheresis

Question 22

Cryoprecipitate is indicated in patients with massive bleeding and _________________, but this condition is very rarely seen.

Answer 22

very low fibrinogen (hypofibrinogenaemia)