4.3.4: Blood groups and transfusion medicine Flashcards
How many equine blood groups are there and what are they called?
- 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
How should you select an equine blood donor?
- 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
What are the feline blood groups and which ones have antibodies against each other?
- 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
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What happens if you give Type A blood to a Type B cat?
- Severe acute intravascular haemolysis of Type A blood
- Within seconds of receiving transfusion
- May be fatal!
What happens if you give Type B blood to a Type A cat?
- Extravascular haemolysis (milder clinical signs than intravascular)
- Low half-life of RBCs
- PCV will fall to pre-transfusion level within days
True/false: in an emergency, you can get away without blood-typing donor and recipient cats.
False
Always blood-type even in an emergency!
What is feline neonatal isoerythrolysis?
- 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)
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What canine blood groups are there and which one(s) have most transfusion significance?
- 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
True/false: most dogs do not have pre-formed antibodies against non-self canine blood types.
True
What blood type should you give to a DEA 1 +ve dog?
DEA 1+ve blood
Where possible give +ve to +ve, and -ve to -ve
True/false: in an emergency, you can give a canine patient DEA 1-ve blood.
True
But in emergencies only; this is not recommended.
What happens if you give DEA 1 +ve blood to a DEA 1 -ve patient?
- 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!
What happens if you give DEA 1 -ve blood to a DEA 1 +ve dog?
- 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)
What is cross-matching and why would you do it?
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
When should you cross-match?
- 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
What are some imminent triggers for blood transfusion?
- 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
What is a single unit of whole blood? What is fresh vs stored?
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
Cryoprecipitate and its uses
- 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
Autologous transfusion and its benefits
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
Canine blood donors must be…
- Fit and healthy
- 1-8 y.o.
- > 25kg
- Good temperament
- Never travelled abroad
- Vaccinated
- Not on any medication
Feline blood donors must be…
- Healthy
- 1-8 y.o.
- > 4kg lean bodyweight
- Preferably indoor cat
- (Do FeLV/FIV testing if outdoor cat)
What sedative/ anaesthetic combination could you give to a feline blood donor?
Ketamine + midazolam
Volume to transfuse =
(Target PCV- recipient PCV)/ Donor PCV x kg x N
Where N = 90 (dogs), N= 60 (cats)
2ml tranfused whole blood/kg of recipient weight raises PCV by
1%
1ml transfused pRBCs/kg recipient weight raises PCV by
1%
What is an appropriate transfusion rate?
- 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
Clinical presentation of transfusion reaction
- Increase in temperature
- Change in HR/RR
- Change in mm colour
- Visible oedema
- GI signs
More severe signs also possible
Clinical signs of acute haemolytic transfusion reaction
This occurs when there is blood type incompatibility
* Fever
* Tachycardia
* Dyspnoea
* Muscle tremors
* Vomiting
* Weakness
* Collapse
* Haemoglobinaemia
* Haemoglobinuria
* Shock
* Death
Treatment of acute haemolytic transfusion reaction
- Stop transfusion immediately
- Give IV fluids
- ± corticosteroids
Delayed haemolytic reaction
- Extravascular haemolysis
- Occurs 3-21 days post-treatment
- -> reduced lifespan of donated erythrocytes
Clinical signs and treatment of delayed haemolytic reaction
- Hyperbilirubinaemia
- ± bilirubinuria
Specific treatment not generally required
