Blood transfusion

Question 1

how does group and screen work

Answer 1

group - test patients antigens vs known A, B group RBCs (reverse group) and test patients RBCs vs known anti A (forward group)

screen -Use 2 or 3 reagent red cells containing all the important red cell
antigens between them
• Screen by incubating the patient’s plasma and screening cells
using IAT** technique
**INDIRECT ANTIGLOBULIN TECHNIQUE (bridges red cells coated
by IgG, which can’t themselves bridge 2 red cells – to form a
visible clump. Takes 30 mins’ incubation at 37°C)

Question 2

how does electronic crossmatch work

Answer 2

Electronic issue (EI) is the selection and issue of red cell units where compatibility is 
determined by IT system, without physical testing of donor cells against patient plasma

Question 3

how does serological crossmatch work

Answer 3

1)FULL CROSSMATCH
INDIRECT ANTIGLOBULIN TECHNIQUE
Patient plasma incubated with donor red cells at 370C for 30-40
mins, will pick up antibody antigen reaction that could destroy the
red cells and cause extravascular haemolysis
ADD ANTIGLOBULIN REAGENT (AHG)

2)
IMMEDIATE SPIN (SALINE, ROOM TEMPERATURE)
Incubate patient plasma and donor red cells for 5 minutes only
and spin, will detect ABO incompatibility only

Question 4

what are the 3 pillars of patient blood management

Answer 4

optomise haemopoisis, bleeding, tolerance of anaemia

Question 5

patient information and consent

Answer 5

1. ‘Valid’ consent is required for transfusion (verbal & written),
2. Alternatives should be considered if appropriate
   a) Iron / B12 / EPO / Folate
   b) Cell Salvage
3. If transfused in an emergency, patient must be informed afterwards
4. Involve patients in the process to ensure they get the right blood
   and the right ‘special requirements’

Question 6

red cells transfusion

Answer 6

Give ABO/D compatible
Group O (negative) in 
emergency
Consider special 
requirements
Stored at 40 C for 35 
days. 
Must be transfused 
within 4 hours of 
leaving fridge
Transfuse 1 unit RBC 
over 2-3 hours

Question 7

Platelets

Answer 7

ABO/D antigens weakly 
expressed 
Should be D 
compatible
Consider special 
requirements
If group O given to A, B 
or AB patients select 
‘high-titre’ negative
(anti-A/B antibodies)
Stored at 20 0 C for 
7days
Transfuse 1 unit of 
platelets over 20-30 
minute

Question 8

FFP

Answer 8

Give ABO compatible 
(D group does not matter)
AB plasma can be given to all groups as 
it has no anti-A/B antibodies but it is in 
short supply
No need to cross match but does take 
30-40 minutes to thaw
Once thawed can be 
kept at 4 0C for 24 
hours
Transfuse 1 unit over 
20-30 minutes

Question 9

Cryoprecipitate

Answer 9

Give ABO compatible 
(D group does not matter)
AB plasma can be given to all groups as 
it has no anti-A/B antibodies but it is in 
short supply
No need to cross match but does take 
30-40 minutes to thaw

nce thawed has to 
kept at room 
temperature and use 
within 4 hours
Transfuse 1 unit over 
20-30 minutes

Question 10

what is maximum surgical blood ordering schedule

Answer 10

MSBOSMSBOS is based agreement between surgeons and transfusion lab about
predictable blood loss for ‘routine’ planned surgery.
Junior doctors / nurses doing pre-admission clinics have some idea what is
normal

Question 11

what percentage blood loss is major

Answer 11

30%

Question 12

when is platelet transfusion contraindicated

Answer 12

heparin induced thrombocytopenia thrombosis and TTP

Question 13

how much does the platelet count go up by in one dose

Answer 13

30-40

Question 14

platelet indication

Answer 14

massive transfusion, prevent bleeding post chemo, during surgery, platelet dysfunction or immune activebleeding

Question 15

FFP indication

Answer 15

massive transfution to treat coagulopathy, aim to get PT:APTT <1.5, liver disease, replacement of single coagulation factor deficiency, DIC, TTP,

Question 16

what does cryoprecipitate contain

Answer 16

fibrinogen mainly, fVIII, vwf, fibronectin, FXIII, IgA, albumin

Question 17

cryoprecipitate indication

Answer 17

fibronogen low

Question 18

can u do pre-eperative autologous deposti in the UK

Answer 18

no

Question 19

whenb would u give CMV negative blood

Answer 19

neonatal, pregnant

Question 20

when would you give washed blood

Answer 20

severe allergic reaction to plasma proteins

Question 21

What are the acute adverse reactions to transfusion

Answer 21

Acute haemolytic (ABO incompatible)
2. Allergic/anaphylaxis
3. Infection (bacterial)
4. Febrile non-haemolytic
5. Respiratory 
• Transfusion associated circulatory 
overload (TACO)
• Acute lung injury (TRALI)

Question 22

what are the delayed adverse reactions to transfusion

Answer 22

1. Delayed haemolytic transfusion reaction 
(antibodies)
2. Infection 
viral, malaria, vCJD
3. TA-GvHD
4. Post transfusion purpura
5. Iron overload

Question 23

how to detect an acute reaction

Answer 23

Monitoring may be the ONLY way to detect
reaction if patient unconscious
 Baseline temp, pulse, respiratory rate, BP
before transfusion starts
 Repeat after 15 mins (as most, but not all,
reactions will start within 15 mins)
 Ideally repeat hourly and at end of
transfusion (as occasionally reactions start
after transfusion finished

Question 24

febrile non haemolytic transfusion reaction

Answer 24

During / soon after transfusion (blood or platelets),
rise in temperature of 10C, chills, rigors
Common before blood was leucodepleted, now rarer
Have to stop or slow transfusion; may need to treat with
paracetamol
Cause: White cells can release cytokines during storage

Question 25

allergic transfusion reactions

Answer 25

Common especially with plasma Mild urticarial or itchy rash sometimes with a wheeze During or after transfusion Usually have to stop or slow transfusion IV antihistamines to treat (and prevent in future if recurrent) Cause: • Allergy to a plasma protein in donor so may not recur again, depending on how common the allergen is • Commoner in recipients with other allergies and atop

Question 26

wrong blood abo reaction

Answer 26

Symptoms and signs of acute intravascular haemolysis- IgM • Restless, chest/ loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later); • ↓BP & ↑HR (shock), ↑Temp Stop transfusion – check patient / component Take samples for FBC, biochemistry, coagulation, Repeat x-match and Direct Antiglobulin Test (DAT) Discuss with haematology doctor ASAP

Question 27

bacterial contamination

Answer 27

Restless, fever, vomiting, flushing, collapse. ↓BP & ↑HR (shock), ↑Temp •Bacterial growth can cause endotoxin production which causes immediate collapse •From the donor (low grade GI, dental, skin infection) •Introduced during processing (environmental or skin) •Platelets >red cells > frozen components (storage temp)

Question 28

anaphylaxis

Answer 28

“Severe, life-threatening reaction soon after start of transfusion” • ↓BP & ↑HR (shock), • very breathless with wheeze, • often laryngeal &/or facial oedema Mechanism: IgE antibodies in patient cause mast cell release of granules & vasoactive substances Most allergic reactions are not severe, but few are e.g. in IgA deficiency IgA deficiency • 1:300 - 1:700 (common); where in 25%, anti-IgA antibodies develop in response to exposure to IgA (transfusion – especially with plasma); • But only minority ever have transfusion reactions- frequency is 1:20,000 - 1:47,000

Question 29

Transfusion associated circulatory overload

Answer 29

Pulmonary oedema / fluid overload; • Often lack of attention to fluid balance, especially in cardiac failure, renal impairment, hypo-albuminaemia, those on fluid replacement, very young, very small and very old. • Clinical features: SOB, ↓SAO2 , ↑HR, ↑BP • CXR: fluid overload / cardiac failure

Question 30

Transfusion associated lung injury

Answer 30

acute lung injury/ARDS • SOB, ↓O2, ↑HR, ↑BP; (similar to TACO) • CXR: bilateral pulmonary infiltrates during/within 6 hr of transfusion, not due to circulatory overload or other likely causes Mechanism • Anti-wbc antibodies (HLA or neutrophil Abs) in donor • Interact with corresponding ag on patient’s wbc’s • Aggregates of wbc’s get stuck in pulmonary capillaries → release neutrophil proteolytic enzymes & toxic O2 metabolites → lung damage Mechanism not fully understood, antibodies don’t always cause problems • Prevention - male donors for plasma & platelets (no pregnancy or transfusion, so no HLA/HNA antibodies

Question 31

Transfusion associated graft versus host disease

Answer 31

• Rare, but always fatal (death weeks to months post transfusion) • Donor’s blood contains some lymphocytes (able to divide) • Normally, patient’s immune system recognises donor’s lymphocytes as ‘foreign’ and destroys them • In ‘susceptible’ patients (e.g... very IS) - lymphocytes not destroyed • Lymphocytes recognise patient’s tissue HLA antigens as ‘foreign’ – so attack patient’s gut, liver, skin and bone marrow - • Prevent: irradiate blood components for very immunosuppressed; or patients having HLA matched components. • Clinical features - severe diarrhoea, liver failure, skin desquamation, bone marrow failure

Question 32

Post transfusion purpura

Answer 32

• Purpura appears 7-10 days after transfusion of blood or platelets and usually resolves in 1 to 4 weeks but can cause life threatening bleeding • Affects HPA -1a negative patients - previously immunised by pregnancy or transfusion (anti-HPA-1a antibody) • ?exact mechanism of own platelet destruction, as HPA-1a negative! ?innocent bystander mechanism • Treatment – infusion of IVIG

Question 33

Iron overload

Answer 33

If lots of transfusion (e.g. >50) over time accumulate iron (not excreted); 200-250mg of iron per unit of blood • Can cause organ damage - liver, heart, endocrine etc • Prevent by iron chelation (Exjade) with transfusions once ferritin >1000 e.g. used in Thalassaemia / Sickle cell disease - regular transfusions

Question 34

Treatment of rhesus disease

Answer 34

All pregnant women have G&S at around 12 weeks (booking) and again at 28 weeks to check for RBC Antibodies. If antibody present:  check if father has the antigen (so baby could inherit it)  monitor level of antibody (high or rising - more likely to affect fetus)  Check ffDNA sample  Monitor fetus for anaemia – MCA Doppler ultrasound  Deliver baby early, as HDN gets a lot worse in last few weeks of pregnancyIf necessary, intra-uterine transfusion can be given to fetus  Specialised centres, highly skilled - needle in umbilical vein  At delivery - monitor baby’s Hb and bilirubin for several days as HDN can get worse for few days  Can give exchange transfusion to baby if needed to bilirubin and Hb; plus phototherapy to bilirubin

Question 35

what is non invasive fetal genotyping

Answer 35

NHSBT offers fetal genotyping - support for routine maternity and transfusion services both nationally and internationally. • A rapid, non-invasive, convenient and reliable service for prediction of fetal D, C, c, E and K status, using cell-free fetal DNA in maternal blood for women who have alloantibodies. • Upon identification, mothers can then be informed and prepared for further careful monitoring during their pregnancy. • Also identifies pregnant women who have antigen-negative fetuses and who therefore are not at danger from HDF

Question 36

what are the clinical features of haemolytic disease of the newborn

Answer 36

Only IgG antibodies can cross the placenta.  If mother has high levels of IgG antibody - it can destroy fetal red cells, if they are positive for the corresponding antigen Fetal anaemia (haemolytic) Haemolytic disease of newborn (anaemia plus high bilirubin - which builds up after birth as no longer removed by placenta, hydrops fetalis, kernicterus