Blood transfusions - science and clinical practice

Question 1

How are A and B antigens made?

Answer 1

by action of transferase enzymes on H, adding either:

• N acetyl galactosamine (A)
• galactose (B)

Question 2

What is the bombay group?

Answer 2

they are a very small group of people that don’t have H antigens -
have anti-H abs
- therefore they can’t be given any of the ABO blood groups

Question 3

Why is ABO blood groups the most important?

Answer 3

1) people who don’t have the antigen have the corresponding Ab => only way you make the Ab is if you are exposed to the antigen whereas in ABO this doesn’t happen

2) type of antibody
= anti A /B = IgM => core important function of it id very sticky therefore activates complement on its own => immediate lyse if need too

Question 4

What is the % distribution of the different ABO blood groups in the UK?

Answer 4

O= 45%
A= 43%
B=9%
AB = 3%

O= universal donor 
AB= universal recipient

Question 5

What are the “other” blood groups?

Answer 5

Rh "rhesus" - C c D E e 
Kell - 90% of pop are kell -ve 
Duffy - Fya Fyb 
Kidd - Jka Jkb 
M N S s 
these are the key other ones that are tested for in group and save test - these are generally IgG antibodies

Question 6

What are the key characteristics of IgG antibodies?

Answer 6

stick to foreign particles
facilitate their destruction in the spleen
engulfed by macrophages
slow process

Question 7

What are the key characteristics of IgM antibodies?

Answer 7

stick to foreign particles
cause immediate activation of complement
occurs in blood vessels
acute and dramatic process

Question 8

What does it mean by forward blood group?

Answer 8

at the blood banks they are looking at antigens on red cell surface to help identify what blood group someone is

Question 9

Why do antibodies usually form?

Answer 9

naturally e.g. anti- a/b
transfusion
pregnancy

Question 10

How much incorrect blood (group) can kill a person?

Answer 10

10ml e.g. giving A to O - haem is very nephrotoxic

Question 11

Where does blood come from?

Answer 11

All comes from blood donors - static donor centres and blood mobile centres

Question 12

How often can blood donors donate?

Answer 12

M- every 12 weeks

F - every 16 weeks - more likely to be iron deficient

Question 13

Why is blood depleted of leucocytes?

Answer 13

because it reduces risk of CJD

Question 14

How are red cells stored? How long should they be transfused over ?

Answer 14

stored at 4 degrees with a shelf life of 35 days (only be out of storage for 30 mins)
transfuse over 2-3 hours
plasma reduced; optimal additive solutions - SAGM

Question 15

How do you mitigate transfusion overload?

Answer 15

transfuse the blood slowly however youve only got 4 hours to transfuse it over

Question 16

Why are red cells stored at 4 degrees?

Answer 16

reduce risk of proliferation of bacteria if contaminated

Question 17

What is meant by a-foresis platelets?

Answer 17

take red cells out and add different ones

Question 18

What is the single dose of platelets given? How are platelets stored and how long can they be transfused over?

Answer 18

dose = 1 unit platelets (4WB donations or 1 apheresis)
stored at ambient temperature of 22 degrees with a shelf-life of 7 days - if they are stored in the fridge the platelets are more active
transfuse over 30 to 60 minutes

Question 19

Which patients get the majority of platelet donations?

Answer 19

chemo patients to help mitigate bleeding

Question 20

What is a normal dose of plasma and how is it stored?

Answer 20

FFP - stored frozen; allow 30 mins to thaw
12-15ml/kg; 3-4 units per dose
used to correct deranged clotting - relatively dilute way of giving clotting factors
can be kept in a freezer for 3 yrs

Question 21

What are the universal donor products (red cells, plasma, platelets)?

Answer 21

red cells = O Rhd negative
plasma = AB (A) - struggle to give AB because its so rare- anti-B reaction is less of a problem than anti-A therefore giving A plasma is generally fine
platelets = AB RhD neg (A) - A is much more common

Question 22

What are the universal recipient products (red cells, plasma, platelets)?

Answer 22

red cells = AB RhD pos
plasma = O
platelets = O RhD neg

Question 23

What questions need to be considered when deciding whether or not to transfuse someone?

Answer 23

• why are they anaemic/thrombocytopenic/coagulopathic?
• what else can be done to correct it?
• how long will that take? Can we wait?
• are they bleeding?
• are you giving prophylaxis or treatment ?=> platelet transfusion to reduce risk of bleeding

Question 24

When in iron deficiency do you do a blood transfusion?

Answer 24

only transfuse if they are at high risk of cardiac event or very dizzy

Question 25

What are the triggers for red cell transfusion?

Answer 25

dose - approx increment of 10g/L per unit for an average 70kg adult

• acute blood loss with haemodynamic instability
• Hb <70g/L stable patient
• Hb <80g/L if cardiovascular disease
• chronic transfusion dependent anaemia (Hb threshold <80g/L initially, but adjusted to patient)

rare that you need to give more than one unit

Question 26

What are the triggers for platelet transfusion?

Answer 26

dose - 1 unit (should increase platelet count by 30)

• prophylactic platelet transfusion
• prior to invasive procedure or therapy =only lasts for a few days so give as close to surgery as possible
• therapeutic use to treat significant bleeding
• specific clinical condition
• platelet dysfunction

our normal platelet count is 150-400 so there is a massive reserve

Question 27

What are the triggers for fresh frozen plasma transfusion?

Answer 27

dose - 15ml/kg body weight - often equivalent to 4 units in adults

• major haemorrhage
• PT ratio/INR <1.5 with bleeding
• PT ratio /INR <1 and pre-procedure
• Liver disease with PT ration/INR <2 and pre-procedure

use in preventing bleeding is minimally justified

Question 28

What are the triggers for cryoprecipitate transfusion?

Answer 28

dose - 2 pooled units equivalent to 10 individual units, will increase fibrinogen by approx 1g/L
- clinically significant bleeding and fibrinogen <1.5g/L
- fibrinogen <1g/L and pre-procedure
very high MW stuff

Question 29

What is the process of taking someones blood?

Answer 29

1) positively identify the patient
2) check details against their wristband
3) obtain verbal consent
4) draw sample
5) label the sample by hand at the bedside
6) check the labelled sample against the wristband

Question 30

What is classed as major haemorrhage?

Answer 30

loss of more than one blood vol within 24 hours (around 70ml/kg , >5L in 70kg adult)
50% total blood vol lost in less than 3 hours
bleeding in excess of 150ml/L

Question 31

What should you do in the instance of major haemorrhage?

Answer 31

give red cells + plasma = outcome is better

- 4 units red cells + plasma

Question 32

What is tranexamic acid?

Answer 32

it is a clot stabiliser and used in major haemorrhage to prevent fibrinolysis

Question 33

What are the IMMUNE adverse effects of transfusion?

Answer 33

wrong blood
febrile non-haemorrhagic transfusion reaction =>give unit of blood get a bit of a temp, its fine, just slow transfusion and give paracetamol
allergic- tends to be more common with plasma
PTP
TRALI
TA-GvHD
immunomodulation

Question 34

What are the INFECTIOUS adverse effects of transfusions?

Answer 34

viral 
bacterial, syphilis 
parasites
prions
?new agents in future

Question 35

What are the OTHER adverse effects of transfusions?

Answer 35

iron overload 
fluid overload (TACO)

Question 36

What are the top 3 serious risks with transfusions and what are the top 3 commonest?

Answer 36

serious

1) ABO incompatibility
2) bacterial infection
3) anaphylaxis

common

1) TACO
2) FNHTR
3) Allergic

Question 37

What are the top 3 serious risks with transfusions and what are the top 3 commonest?

Answer 37

serious

1) ABO incompatibility
2) bacterial infection
3) anaphylaxis

common

1) TACO
2) FNHTR
3) Allergic

biggest risk to patients is that a healthcare professional will make a mistake

Question 38

What are the risky bacterial infections that could arise?

Answer 38

bacterial sepsis => especially if a bacterial endotoxin is produced e.g. E.coli
hypotension, fever, tachycardia within mins of starting the transfusion
acquired from donor skin - reduced risk by stringent cleaning of skin, divert pouch and bacterial screening

it can be fatal

Question 39

What element is critical at all stages of a blood transfusion?

Answer 39

patient identification - ask the pt, check the wristband, check the blood label, check the prescription chart, check the notes

Question 40

When should the first set of observations be checked after starting a blood transfusion?

Answer 40

baseline
15 minutes
end of transfusion

Question 41

What pulmonary complications can arise from transfusions and who is at risk?

Answer 41

Transfusion associated circulatory overload (TACO)
pts at risk: 
- elderly
- pre-existing disease 
- low weight pts given large vol transfusions 
- renal impairment
- liver impairment 
- concomitant fluids 
- diuretic use

Question 42

What is TRALI?

Answer 42

Transfusion related acute lung injury (TRALI)

- transfused ab in donor pts interact with white cells

Question 43

What is acute haemolytic reaction?

Answer 43

due to ABO mismatch

• can be fatal soon after starting transfusion
• immediate complement mediated red cell lysis due to IgM anti-A/B
• hypotension, tachycardia, fever, renal failure, DIC, death
• as little as 10ml can be fatal

Question 44

How is acute haemolytic reactions prevented/reduced?

Answer 44

2 sample rule

strict protocol when taking samples, transporting and administering blood