4.3.4: Blood groups and transfusion medicine

Question 1

How many equine blood groups are there and what are they called?

Answer 1

• 7 groups
• A, C, D, K, P, Q, U
• Lowercase letters represent allelic factors
• Aa, Qa, Ca are the most immunogenic blood groups
• Majority of horses lack naturally occurring antibodies

Question 2

How should you select an equine blood donor?

Answer 2

• Donors should ideally be geldings
• Aa, Qa, Ca = most immunogenic blood groups so ideally from a breed (e.g. standardbred) with a low prevalence of these
• Cross-matching is essential

Question 3

What are the feline blood groups and which ones have antibodies against each other?

Answer 3

• Types: A, B and AB (rare)
• Type A carry weak anti-Type B antibodies
• Type B carry very strong anti-Type A antibodies
• Type AB carry no antibodies against type A or B
• Mik = newly recognised blood group in DSH

Question 4

1

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Question 5

2

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Question 6

3

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Question 7

4

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Question 8

5

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Question 9

6

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Question 10

7

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Question 11

8

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Question 12

9

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Question 13

What happens if you give Type A blood to a Type B cat?

Answer 13

• Severe acute intravascular haemolysis of Type A blood
• Within seconds of receiving transfusion
• May be fatal!

Question 14

What happens if you give Type B blood to a Type A cat?

Answer 14

• Extravascular haemolysis (milder clinical signs than intravascular)
• Low half-life of RBCs
• PCV will fall to pre-transfusion level within days

Question 15

True/false: in an emergency, you can get away without blood-typing donor and recipient cats.

Answer 15

False
Always blood-type even in an emergency!

Question 16

What is feline neonatal isoerythrolysis?

Answer 16

• When Type A or AB kittens are born from a Type B queen
• “Fading” kittens
• Breeders should be urged to type the queen (and then the tom if the queen is found to be Type B)

Question 17

1

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Question 18

2

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Question 19

3

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Question 20

4

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Question 21

What canine blood groups are there and which one(s) have most transfusion significance?

Answer 21

• DEA 1, 3, 4, 5, 6, 7, 8; DAL; Kai 1 and 2
• We no longer use subgroups e.g. 1.1, 1.2 etc.
• DEA 1 antigen has the most transfusion significance (highly antigenic) and is the one we have a commercial test kit for
• 70% of dogs are DEA 1 +ve
• 30% of dogs are DEA 1 -ve

Question 22

True/false: most dogs do not have pre-formed antibodies against non-self canine blood types.

Answer 22

True

Question 23

What blood type should you give to a DEA 1 +ve dog?

Answer 23

DEA 1+ve blood
Where possible give +ve to +ve, and -ve to -ve

Question 24

True/false: in an emergency, you can give a canine patient DEA 1-ve blood.

Answer 24

True
But in emergencies only; this is not recommended.

Question 25

What happens if you give DEA 1 +ve blood to a DEA 1 -ve patient?

Answer 25

* You will sensitise them * This means if they later have more DEA 1 +Ve blood, they could suffer an **acute haemolytic transfusion reaction** which could be fatal!

Question 26

What happens if you give DEA 1 -ve blood to a DEA 1 +ve dog?

Answer 26

* No adverse effects * However this is not a good use of DEA 1 -ve blood (this is in the minority and should be reserved for DEA 1 -ve patients)

Question 27

What is cross-matching and why would you do it?

Answer 27

**Cross-matching:** in-vitro tests looking for potential reactions between a donor's and a patient's blood. These show as agglutination or haemolysis. * Cross-match for additional blood groups that don't have specific in-house tests

Question 28

When should you cross-match?

Answer 28

* Cats have naturally occurring antibodies -> cross-match prior to transfusion and definitely prior to subsequent transfusion * Cross-match dogs if recipient has been previously transfused >4 days prior/ if history of previous transfusion reaction/ if transfusion history unknown

Question 29

What are some imminent triggers for blood transfusion?

Answer 29

* Evidence for circulatory collapse * Rapid drop in PCV to <20% in dogs * Rapid drop in PCV to <15% in cats * Absolute PCV of 15-20% depending on history and clinical signs * PCV <10-12% -> organ hypoxia is imminent! * Signs of organ hypoxia e.g. CNS * Concern that PCV will fall over period of time when transfusion would be difficult to organise

Question 30

What is a single unit of whole blood? What is fresh vs stored?

Answer 30

450ml * Fresh = transfused within 8 hrs collection. Contains all blood components. * Stored = refrigerated<4C and stored for up to 3 weeks. Lacks platelets, WBCs, and labile clotting factors e.g. Factors V and VIII and vWF. * Generally used in acute blood loss/active bleeding

Question 31

**Cryoprecipitate** and its uses

Answer 31

* **Cryoprecipitate:** plasma fraction separated from fresh frozen plasm * Contains concentrated labile clotting factors including fibrinogen, vWF, Factor VIII * Shelf life 1 year * Used in pre-treatment for vWD

Question 32

**Autologous transfusion** and its benefits

Answer 32

**Autologous transfusion:** the collection of blood from a single patient and re-transfusion back to the same patient when required. ✅ Reducing potential for exposure to allogenic blood ✅ Reduces risk of new infectious diseases ✅ Reduces chances of transfusion reactions ✅ Immediate availability

Question 33

Canine blood donors must be...

Answer 33

* Fit and healthy * 1-8 y.o. * >25kg * Good temperament * Never travelled abroad * Vaccinated * Not on any medication

Question 34

Feline blood donors must be...

Answer 34

* Healthy * 1-8 y.o. * >4kg lean bodyweight * Preferably indoor cat * (Do FeLV/FIV testing if outdoor cat)

Question 35

What sedative/ anaesthetic combination could you give to a feline blood donor?

Answer 35

Ketamine + midazolam

Question 36

Volume to transfuse =

Answer 36

(Target PCV- recipient PCV)/ Donor PCV x kg x N ## Footnote Where N = 90 (dogs), N= 60 (cats)

Question 37

2ml tranfused whole blood/kg of recipient weight raises PCV by

Answer 37

1%

Question 38

1ml transfused pRBCs/kg recipient weight raises PCV by

Answer 38

1%

Question 39

What is an appropriate transfusion rate?

Answer 39

* In the stable patient: 0.5-1.0ml/kg/hr; monitor for 15-30 mins for reaction, then can increase to 4-6ml/kg/hr * The unit should be given within 4hrs * In an emergency (severe acute haemorrhage), give red cells as fast as necessary

Question 40

Clinical presentation of transfusion reaction

Answer 40

* Increase in temperature * Change in HR/RR * Change in mm colour * Visible oedema * GI signs More severe signs also possible

Question 41

Clinical signs of **acute haemolytic transfusion reaction**

Answer 41

This occurs when there is blood type incompatibility * Fever * Tachycardia * Dyspnoea * Muscle tremors * Vomiting * Weakness * Collapse * Haemoglobinaemia * Haemoglobinuria * Shock * Death

Question 42

Treatment of **acute haemolytic transfusion reaction**

Answer 42

* Stop transfusion immediately * Give IV fluids * ± corticosteroids

Question 43

Delayed haemolytic reaction

Answer 43

* Extravascular haemolysis * Occurs 3-21 days post-treatment * -> reduced lifespan of donated erythrocytes

Question 44

Clinical signs and treatment of **delayed haemolytic reaction**

Answer 44

* Hyperbilirubinaemia * ± bilirubinuria Specific treatment not generally required