Blood transfusion

Question 1

Where does the blood come from

Answer 1

Human source - no synthetics yet (research) - not risk free (HIV, Hep B- screen blood first)
Scarce resource
1 donor gives approx 1 pint (unit) - max. every 4 months
Need 9,000 units of blood/day in U.K. (can’t stockpile - blood shelf life = 5 weeks)
Therefore use carefully

Question 2

Describe the importance of using blood appropriately

Answer 2

Balance between benefits vs risks ie: when no safer alternative available eg:
If massive bleeding - if ‘plain fluids’ not sufficient
If anaemic - if iron/ B12/ folate not appropriate ( can give these components separately as plasma)

Doctor’s decision: has to prescribe

Question 3

Describe the history of blood transfusions

Answer 3

Early human to human transfusion - fatal
1901 - Landsteiner (Nobel Prize winner) discovered ABO blood groups
Since then - test blood groups of patient and donor (and X-match)
Should not die of ABO incompatible blood transfusion (yet a death and several
in ITU each year in UK)

Question 4

Summarise the ABO blood groups

Answer 4

Most important of all blood groups
A and B antigens on red cells formed by adding one or other sugar residue onto a common glycoprotein and fucose stem on red cell membrane
Group O has neither A or B sugars - stem only

Question 5

Summarise the genes for the ABO blood group

Answer 5

Antigens determined by corresponding genes
A gene codes for enzyme which adds N-acetyl galactosamine to common glycoprotein and fucose stem
B gene codes for enzyme which adds galactose
A and B genes are co-dominant
O gene is ‘recessive’
eg: person is blood group A - genes could be AA or OA

This enzyme is a transferase

Question 6

What glycoprotein and fructose stem is common to everyone

Answer 6

H stem

Question 7

Describe the inheritance pattern for the ABO blood groups

Answer 7

A and B genes are codominant
O is ‘recessive’ because it doesn’t code for anything at all
So you need to be homozygous for O (OO) to be in blood group O

Question 8

Describe the ABO antibodies

Answer 8

Person has antibodies against any antigen NOT present on own red cells
Naturally occurring (nearly from birth) - IgM: it is a ‘complete’ antibody, so:- fully activates complement cascade to cause haemolysis of red cells
o I.E. patient with group A will have antibodies against group B blood.

Question 9

Describe the consequences of an ABO incompatible transfusion

Answer 9

a) In a patient who has received an ABO incompatible transfusion, where patient has the corresponding antibody (eg: blood group A given to patient who is group O - so has anti-A and anti-B) - then antibody/ antigen interaction often fatal
b) In laboratory tests, IgM Abs interact with corresponding ag to cause agglutination eg: if patient is group B, he has anti-A antibody in plasma - when add to group A cells - agglutination seen (clump) - shows cells are incompatible

Question 10

Describe the pathogenesis of an incompatible transfusion

Answer 10

Incompatible transfusion: produces fatal antibody-antigen interaction; IgM meet complementary antigens, crosslink and activate whole complement cascade, so membrane attack complex causes cell lysis (of red cells), leading to release of toxic products such as Hb and a cytokine storm (leading to shock)

This is often FATAL
It can lead to cytokine storm, lysis, cardiovascular collapse and death

IgM is a complete antibody- so it activates the full complement cascade.

o IgM also cause agglutination of the red cells.

Question 11

Summarise the proportions of the different ABO blood groups

Answer 11

A- has A antigens in blood, anti-B antibodies in plasma- 42%

B- has B antigens in blood, anti-A antibodies in plasma, 8%

O- no antigens in blood, anti-A and anti-B antibodies in plasma 47%

AB, AB antigens in blood, not antibodies, 3%

§ OO- is the universal donor.
§ AB+ is the universal receive

Question 12

What is done before transfusion to ensure that the donor’s and recipents blood are compatibile

Answer 12

A blood sample is taken from the patient and the ABO blood group is determined (test with anti-A and anti-B antibodies)
Select a donor unit of the same group
CROSS-MATCH: patient’s serum is mixed with donor red cells – it should NOT react (if it reacts then it shows that it is incompatible)

Question 13

Describe the antigens of the RH group

Answer 13

RhD is the most important
Blood groups: RhD positive (if have D antigen) or RhD negative (if not)
Genes for RhD groups:
D - codes for D antigen on red cell membrane
d - codes for no antigen and is recessive
Therefore dd = no D antigen = RhD negative
DD or Dd = D antigen present = RhD positive
85% of people are RhD positive; 15% are RhD negative (patient’s ABO and Rh D group usually shortened eg: O pos means ABO group O and Rh D pos)

Question 14

When can patients who are RhD negative make D antibodies

Answer 14

People who lack the RhD antigen (ie: RhD negative) CAN make anti-D antibodies AFTER they are exposed to the RhD antigen - either by transfusion of RhD positive blood or in women, if they are pregnant with an RhD positive fetus
Anti-D antibodies are IgG antibodies

Question 15

Describe the key features of the RhD blood group

Answer 15

RhD positive- D positive antigen, no antibodies

RhD negative- D negative antigen, can make anti-D if sensitised

Question 16

What are the implications of anti-D antibodies

Answer 16

1. Future transfusions
   
   • patient must, in future, have RhD neg blood (otherwise his anti-D would react with RhD pos blood - causes delayed haemolytic transfusion reaction - anaemia; high bilirubin; jaundice etc)
2. HDN = haemolytic disease of the newborn
   
   • if RhD neg mother has anti-D - and in next pregnancy, fetus is RhD pos - mother’s IgG anti-D antibodies can cross placenta - causes haemolysis of fetal red cells - if severe: hydrops fetalis; death

Heart failure in fetus- HR increases to try and increase oxygen perfusion of tissues- due to anaemia- will die during pregnancy 
BR toxic (placenta takes out- so not an issue during pregnancy)- causes brain damage- hyper=extension of arms, legs and neck

Question 17

Describe the importance of the RhD group

Answer 17

RhD GROUP - IMPORTANCE = avoid Rh D neg patients making anti-D

Transfuse blood of same RhD group (no harm to give RhD neg to a pos patient - just wasteful!)
O neg used as emergency blood when patient’s blood group not known (NB only 6-7% of donors are O neg)

Question 18

Describe some other blood antigens

Answer 18

Other antigens present on red cells
Don’t routinely match blood for all these, eg Rh group -C, c, E, e; others - Kell, Duffy, Kidd, etc
c and K- can cross the placenta and harm babies.

Question 19

What are the implications of the other red cell groups

Answer 19

About 8% of pts transfused will form Ab to one or more of these antigens
Once have formed antibody must use corresponding antigen negative blood; or else risk of delayed haemolytic reaction (can be severe)

Before each transfusion you should test the patient’s blood sample for red cell antibodies.
So before transfusing a patient, as well as testing the ABO and RhD groups, you must do antibody screening of their plasma.

Question 20

A woman is O positive; her partner is AB positive. Which of these cannot be a child of theirs?

Answer 20

Someone who is AB positive or O positive

Question 21

How do we give blood these days

Answer 21

1 unit (‘pint’) blood collected into a bag containing anticoagulant
No longer routinely give whole blood to patients - use parts needed:
more efficient; less waste as patients don’t
need all the ‘components’;
some components degenerate quickly if
stored as ‘whole blood’
Red cells – concentrated, as plasma
removed; also avoids fluid overloading patients - preventing risk of heart failure in the elderly

Question 22

How do we get the different components of blood

Answer 22

Split one unit of blood by centrifuging whole bag (red cells bottom, platelets middle, plasma top) then squeeze each layer into satellite bags and cut free (closed system) - to prevent risk of bacterial infection

heat seal between different bags

Question 23

What else will be found in the platelet layer

Answer 23

White cells

Question 24

What can the plasma obtained from the donor be split into

Answer 24

FFP (contain all the clotting factors and some fibrinogen)
Cryoprecipitate (containing fibrinogen + factor 8)

Plasma for fractionation (not UK)- pools of thousands of donors- albumin, factor 8, IX immunoglobulins, anti-D etc

Question 25

Describe the key features of administering red cells

Answer 25

1 unit from 1 donor - ‘packed cells’ (fluid plasma removed)
Shelf life 5 weeks; stored at 4oC (fridge)
Give through a ‘blood giving set’ - has filter to remove clumps/debris- contaminated fibrinogen
Rarely need frozen red cells (National Frozen Bank) - for rare groups/ antibodies - poor recovery on thawing - need to add glycerol to prevent ice crystals from forming.

Question 26

Describe the key features of administering FFP

Answer 26

1 unit from 1 donor (300ml) can get small packs for children
Stored at -30oC (frozen within 6h of donation to preserve coag factors)
Shelf life 2 years
Must thaw approx 20-30 mins before use (if too hot, proteins cook)
Give ASAP – ideally within 1h or else coag factors degenerate at room temp
Dose 12-15ml/kg = usually 3 units
Need to know blood group - no x-match, just choose same group (as contains ABO antibodies, which could cause a bit of haemolysis

Question 27

What are the indications for FFP

Answer 27

1. If bleeding + abnormal coag test results (PT, APTT)
   
   • Monitor response - clinically and by coag tests
2. Reversal of warfarin (anticoagulant) eg for urgent surgery (if PCC not available)-= prothrombin complex concentrate- contains 2,7,9 and 10- which warfaring prevents the synthesis of
3. Other conditions occasionally

liver failure- where they can’t make coagulation products.

NB not just to replace volume/ fluid loss

Question 28

Describe the characteristics of administering cytoprecipitate

Answer 28

From frozen plasma thawed at 4-8oC overnight residue remains
Contains fibrinogen and factor VIII
Same as FFP - store at -30oC for 2 yrs
Standard dose = from 10 donors (5 in a pack)
Indications:
If massive bleeding and fibrinogen very low
Rarely hypofibrinogenaemia

Question 29

Describe the key features of administering platelets

Answer 29

1 pool from 4 donors (= standard adult dose) or from 1 donor by apheresis (cell separator machine)
Store at 22oC (Room temp) - constantly agitated- to prevent clumping
Shelf life 5 days only - (risk of bacterial infection)

Question 30

Describe the importance of knowing blood group when administering platelets

Answer 30

No cross-match, just choose same group (as platelets have low levels of ABO antigens on, so wrong group platelets would be destroyed quickly) - and can cause RhD sensitisation, as some red cell contamination

Platelts need to be in plasma to work effectively- so need to match to donor- don’t want to cause haemolysis of the patient- important in surgery

However, for leukaemic patinets- paltelts need to function for about 2 weeks- so you are less bothered about matching.

Question 31

Describe the indications for platelets

Answer 31

Mostly haematology patients with bone marrow failure (if platelets <10 x 109/L)- leukaemia
Massive bleeding or acute DIC- organs clogged by clots- risk of bleeding to due exhaustion of coag factors
If very low platelets and patient needs surgery
If for cardiac bypass and patient on anti-platelet drugs
1 pool is usually enough - rarely need more
Generally, platelets and FFP overused in past - limited resource and cost

Question 32

If you give the wrong FFP, why won’t it kill the patient

Answer 32

If you give the wrong FFP it wont kill the patient because the antibodies are quite dilute but it will haemolyse some of the red cells which is not ideal

Question 33

Explain the purpose of fractionated pools

Answer 33

The plasma of many donors is pooled and put into a fractionating column. This means that various components such as albumin, haemophilia factors and anti-D antibodies can be pulled off.
This is NOT done in the UK.

Question 34

Describe the fractionated products

Answer 34

Factor VIII and IX
For haemophilia A and B respectively (males)
Factor VIII for von Willebrand’s disease
Heat treated - viral inactivation
Recombinant factor VIII or IX alternatives increasingly used, but expensive
Immunoglobulins
IM: Specific - tetanus; anti-D (useful for sensitisation in pregnant women); rabies
IM: Normal globulin - broad mix in population (eg: HAV)
IVIg – pre-op in patients with ITP or AIHA

Factor 8 and 9 = used for haemophilia
Factor 8 – also used for von Willebrand’s disease

Fraction for fator 9- impure- contains 2,7 and 10- used for PCC

Question 35

Describe another fractionated product and its use

Answer 35

Albumin
4.5%
Useful in burns, plasma exchanges, etc
Probably overused (not indicated in malnutrition)- body cannot survive without oncotic pressure of proteins- which are lost in burns patients
20% (salt poor)
For certain severe liver and kidney conditions only

Question 36

What can IVig be used to treat

Answer 36

Pre-op in patients with ITP (immune thrombocytopenic purpura – IVIg helps prevent the destruction of antibody coated platelets in the spleen and liver) and AIHA (autoimmune haemolytic anaemia)

Question 37

Describe the importance of screeing for donors

Answer 37

Aim to keep blood safe for patient (eg transmitting infections; drugs; disease)
By testing for infections (some) - not failsafe
And by questioning for risk behaviour - to exclude them
2. Also aim to prevent harm to donors - by questioning them, to exclude risky ones (eg: people who have heart problems, etc) - screening tests entirely accurate- won’t detect recently acquired infections as levels are too low- so need to screen for risk behaviours

Question 38

Describe some of the limitations in screening for donors

Answer 38

NB ‘window period’ of infections - tests will not show positive! Therefore cannot rely only on testing

Exclude high risk donors
Use voluntary, unpaid donors

Question 39

Name some infections that we screen for

Answer 39

Infections that all blood must be tested for:
Hepatitis B 	- HBsAg, PCR
Hepatitis C	- anti-HCV, PCR             viruses
HIV		- anti-HIV, PCR
HTLV		- anti HTLV
Syphilis	- TPHA (spirochete)
Hepatitis E	- PCR
Some also tested for CMV (virus) 

Particuarly important when giving blood to the immunocompromised

Question 40

What disease can be transmitted via the blood

Answer 40

REMEMBER: prion disease (variant Creutzfeldt-Jakob Disease) can be transferred via the blood.

Question 41

Describe vCJD

Answer 41

NB - many other infections could potentially be transmitted - questionnaire exclude these, eg malaria
prion disease - vCJD
can be transmitted by blood transfusion -
4 cases where recipients had blood from donors who died from vCJD; 3 developed vCJD several years later; 1 had prion detected but asymptomatic & died of other cause
As precaution:
all plasma pooled to make fractionated products now obtained from USA (UK plasma - some used for FFP, the rest thrown away)
all blood components have white cells filtered out (leucodepleted) - in case white cells are essential for uptake of vCJD prion into brain to cause disease

Question 42

What is found in FFP

Answer 42

Thawing FFP in a 4 degrees centigrade fridge over night produces Cryoprecipitate 
It contains: 
· Fibrinogen 
· Factor 8 
· Factor 13 
· Von Willebrand Factor 
· Fibronectin

Question 43

What can cause haemolytic disease of the new born

Answer 43

It is relatively common for a D-negative woman to become sensitized through exposure to foetal D-positive red cells during pregnancy, as her partner is likely to be D-positive (fetomaternal leakage of red cells across the placenta occurs commonly at the time of delivery, but also silent bleeds are not uncommon and may occur during late pregnancy). If an RhD-negative woman develops anti-D antibodies, then in the next pregnancy, the IgG antibodies can cross the placenta and destroy fetal red cells – causing hydrops fetalis or haemolytic disease of the new-born (hdn). It is therefore important not to sensitize RhD negative girls or women of child bearing age by transfusing RhD positive blood.

Question 44

Summarise the selection of blood

Answer 44

Blood selected for transfusion should be ABO and RhD compatible; plus the purpose of compatibility testing is to ensure that the recipient does not have antibodies against blood group antigens present in donor blood selected for transfusion, which could cause haemolysis.
‘Antibody screen’ of recipient plasma to exclude any clinically significant immune antibodies. Recipient plasma is incubated with 2 or 3 different fully typed ‘screening’ red cells, which are known to possess all the blood group antigens which matter clinically. If the screen is negative, any donor blood which is ABO (and D) compatible can be given. If positive, the antibody must be identified with the use of a large panel of red cells; donor units that lack the corresponding blood group antigen are then chosen for cross matching with the recipient’s plasma prior to transfusion.
Compatibility test done between donor red cells and recipient plasma = ‘cross-match’.

Question 45

Describe the importance of careful donor selection

Answer 45

Blood is collected in the UK only from volunteer, unpaid donors, who are between 17-70 years of age. Donors are excluded if they have any disease that might make blood donation hazardous, e.g. cardiovascular/ neurological disease, or if their blood would be hazardous for the recipient (risk of viral, bacterial or parasitic infections, certain diseases or drugs). Donor education and self exclusion of individuals who are at high risk of having contracted blood-borne infectious diseases are essential to ensure that subjects who are in an early infectious stage, but who have not sero-converted (they have not yet developed antibodies, i.e. in the ‘window period’) are not accepted as blood donors.

Question 46

Describe some common causes of donor exclusion

Answer 46

High risk groups:
Men or women who are infected with HIV, hepatitis B or C
Men or women who have injected illegal or non-prescribed drugs,including body-building drugs, at any time
Men or women who have ever been given money or drugs for sex
Men or women who have had sex in the last 12 months with:
anyone in the above groups
a man or woman who may have ever had sex in parts of the world where HIV/AIDS is very common (this includes most African countries except those bordering the Mediterranean)
men who have had oral or anal sex with another man with or without a condom or other form of protection
women who have had sex in the last 12 months with a man who has had oral or anal sex with another man with or without a condom or other form of protection

Question 47

Describe the grouping and screening of donor blood

Answer 47

Every blood donation has the ABO and RhD blood group determined. Also, the other Rh blood groups, namely, C, c, E, e and the K blood group are determined on most donations in the UK.
Every donation is tested to ensure that no strong clinically significant red cell antibodies are present in the donor’s plasma, so that any transfusions containing plasma will only contain ABO antibodies.

Question 48

Describe infection testing of donor blood

Answer 48

NB: The most important step in maintaining a safe blood supply is rigorous donor selection and self-exclusion of subjects at high risk of transmitting blood-borne agents. Testing donations for the relevant agents adds to safety, but no test can pick up all infections, especially early ones. The tests done on every blood donation are shown in the table below. In addition, giving blood only to patients who really need it reduces the risk to patients.

Question 49

Summarise prion disease

Answer 49

Prion proteins have been found in membranes of lymphocytes and platelets and the prions of variant Creutzfeldt-Jacob disease (CJD) are found in lymphoreticular tissues. There have been 4 cases in the UK of variant CJD transmitted by transfusion of blood or blood products in humans, where donors who were entirely well donated then years later developed vCJD. A blood test to exclude any donor with vCJD is not yet available.

Question 50

Which infections may be screened for in some patients

Answer 50

Plus for some donations: Cytomegalovirus (CMV), Trypanosoma cruzi, Malaria

Question 51

Summarise how blood transfusions have changed in recent years

Answer 51

450 ml blood is collected from a donor into a sterile plastic bag containing anti-coagulant. Over the last 25 years, the emphasis in blood transfusion has changed. It is no longer the aim to provide unseparated whole blood, because very few patients require all the components in blood. With improved diagnosis of coagulation factor deficiencies, modern aggressive chemotherapy regimes, bone marrow transplantation, and improved technology, it has become routine to treat patients only with those components which are required – for example platelets, red cells, factor VIII, etc. Component therapy enables more efficient use of blood donations, and less waste of valuable resources. Also mainly due to the publicity given to transfusion-transmitted infections, clinicians are starting to become more conscious than ever that blood should be prescribed only when there is no safer alternative therapy, e.g. iron therapy, intraoperative salvage etc

Question 52

What is most blood given as

Answer 52

A) Red cells – less than 1% of blood is used as ‘whole’ blood in the UK; it is deficient in labile clotting factors and functional granulocytes and platelets. Most blood is given as ‘SAG-M’, where red cells are more concentrated after plasma removal, so that plasma can be used for other purposes, plus this avoids fluid-overloading patients during transfusion.

Question 53

Describe some other preparations of red cells

Answer 53

Plasma reduced RBC
Frozen RBC
RBC SAG-M

Question 54

Describe the different forms of platelet concentrates

Answer 54

B) Platelet Concentrates – available in two forms.
Pooled platelets – platelets from 4 donations pooled to constitute a single adult dose. (Commonest)
Or from a single donor by cell separator machine, equivalent to 4 single donations of platelets.

Question 55

Describe the use of platelets prophylactically

Answer 55

Prophylaxis due to thrombocytopenia (with decreased platelet production e.g. chemotherapy, bone marrow transplant, aplastic anaemia) or defective platelet function
Bleeding becomes likely when platelet count is less than 10×109/l, but can occur at higher levels when there is fever, infection, platelet dysfunction (e.g. post cardiac bypass).

Question 56

Describe the therapeutic uses of platelets

Answer 56

Massive blood transfusion (dilutional thrombocytopenia)
Platelet dysfunction of cardiac bypass, aspirin
NB: Autoimmune Thrombocytopenia (AITP): platelet transfusions are rarely indicated because there is rapid destruction of all platelets by the autoantibody. In this disease, platelets are required only for life-threatening bleeds.
Important to monitor clinical response (not just rise in platelet count).
White Cells – very rarely used except when severe infections occur in neutropaenic patients not responding to antibiotics/antifungal drugs

Question 57

Summarise FFP

Answer 57

Plasma contains clotting factors/ albumin/ immunoglobulins,water, electrolytes.
Once thawed (at 30-37ºC) – deterioration of clotting factors – use as soon as possible
Use ABO compatible, as plasma contains anti-ABO group antibodies
Indications – very few definite indications. Should be given only in patients who are bleeding actively and have abnormal clotting tests or are receiving anticoagulant therapy and need urgent
surgery.

Question 58

Summarise cytoprecipitate

Answer 58

Separated from other plasma constituents by freezing fresh plasma and then allowing it to thaw at 4º-8ºC overnight.
Approximately 3% of the FFP forms a residue – fails to redissolve = cryoprecipitate. Contains factor VIII and fibrinogen. Stored frozen in a small volume of plasma (approximately 15 ml). When
thawed quickly for use, it redissolves in plasma.

Separate from cytosupernatant

Indications:
(i) treatment of DIC, together with other blood components
fibrinogen deficiency

Question 59

Summarise the clinical uses of the different fractionation products

Answer 59

1. Albumin – human albumin solution (HAS) 4.5%. A safe product that is pasteurised and has never been implicated in the transmission of infections.
   Clinical uses: – very few; a highly overused product – hypoproteinaemia, burns, extensive surgery and plasma exchange
2. Factor VIII Concentrate – Large pools of plasma (2,000->5,000 donations) subjected to fractionation and heat treated to eliminate viral transmission.
   Clinical uses: – treatment of haemophilia A (prophylaxis and acute bleeding)
   – von Willebrands’ disease
   NB: Recombinant factor VIII is now given to all new haemophiliacs in the UK.
3. Factor IX Concentrate
   Clinical uses: – treatment of Christmas disease or Haemophilia B (again, recombinant IX available)
4. Normal Human Immunoglobulin: prepared from pooled normal human plasma and contains a mixture of immunoglobulins present in the healthy adult population. Available as IM or IV preparations.
   Indications for use: (a) mostly by IV route – as replacement in immunodeficiency states, ITP or autoimmune haemolytic anaemia. (b) by IM route – prevention of certain infections (by providing broad antibody cover from normal population) e.g. hepatitis A, measles, rubella.
5. Specific Immunoglobulins: fractionated from plasma from selected donors who have a high titre of a specific antibody (from hyperimmune donors) e.g. anti-D Ig, hepatitis B Ig, varicella-zoster Ig, rabies Ig, tetanus Ig, CMV Ig.

also contains anti-thrombin