Transfusion medicine

How do you know if a patient needs a blood transfusion?

• Based on clinical signs

  • Signs suggestive of reduced oxygen provision to tissues —> tachycardia, tachypnoea, lethargy, weakness etc.

• Ensure patients are normovolaemic before deciding whether to transfuse

• Generally looking at PCV of 10-15% for cats and 15-20% for dogs

Which blood products can be used for blood transfusion?

• Replace 'like with like'

• Blood loss —> replace with whole blood or if not available, packed red cells e.g. crystalloid fluid therapy 

• Haemolysis —> Replace with packed red cells 

• Coagulopathy —> Replace with fresh frozen plasma, regular plasma or cryoprecipitate depending on cause 

Why do we need to blood type patients?

• Will influence blood type of blood product

• Ideally give type-matched blood to dogs

  • If unable to blood type dog, administer DEA 1 negative blood to dogs

• Imperative to give type-matched blood to cats

• No strictly necessary for admin of plasma products

What system is used to classify dogs blood types

• Based on Dog Erythrocyte Antigen system

  • One we care about most is DEA 1 blood type- most antigenic

    • So dog can either be DEA 1 -ve or DEA +ve

• Dogs do not have naturally occurring antibodies only develop them following tranfusion- may have acute haemolytic reaction if exposed subsequently

What happens if we give a dog the wrong DEA 1 type blood?

• A DEA 1 –ve dog receiving DEA 1 +ve blood will have a very mild, delayed reaction

• A DEA 1 +ve dog receive DEA 1-ve blood will not demonstrate any signs

• First transfusion usually 'free'

What is the feline blood type system?

• Based on A/B system with A being dominant to B and AB being polygenic

• Cats have naturally occurring antibodies

  • Imperative to give type-matched blood as can have fatal acute haemolytic reactions with wrong type

What happens if we give cats the wrong type of blood?

• Giving B cats type A blood is BAD → severe acute haemolytic reaction

• Giving A cats type B blood is not As Bad → milder, delayed reaction

How can you blood type a patient?

• Gold standard is sending to external lab for confirmation 

• Otherwise use card/casette-based methods

  • Only available for DEA 1 and A/B

    

• Imperative to rule out auto agglutination before using card based method

  

What is cross-matching?

• Detects more haemotological (Type II HS) incompatabilities than blood typing alone

• Will detect the majority of antigen-antibody incompatibilities

• Will not detect non-antibody mediated incompatibilities

What are the different types of cross-matching?

• Major crossmatch —> Recipient antibodies against donor red cells

• Minor crossmatch —> Donor antibodies against recipient red cells

When is it necessary to cross-match patient?

• If has had previous transfusion then imperative

  • Unless within 3-5 days of first transfusion as antibodies will not have formed

• Grey area with need for crossmatch if have received plasma products

• Similarly unclear with previous pregnancies

How do you cross match?

• Laboratory is gold standard

• Rarely get 100% compatible —> choose least risky 

• IDEXX and Pet blood bank will crossmatch and deliver bags to you (takes 24 hours)

• In house gel-based methods are inaccurate and not recommended

How do you know how much blood you should give a placement via tranfusion?

• Restrictive transfusion target —> aim for around PCV 21-25%

• Use formulas as rough guide

• Round up to nearest bag

How should a blood transfusion be administered?

• IV admin

  • Transfusion set with an in line filer

• Intra-osseous also acceptable

• Slow rate initially and then building up thereafter —> generally dose dependent

• Consider equipment, ability to monitor and maintaining sterility is vital

  • blood is growth medium for bacteria

How does the way of administering a blood transfusion differ in dogs and cats?

Dog —> better to administer drip by drip through a transfusion set rather than fluid pump

Cat —> better to administer via syringe driver

How fast should a transfusion be given?

• 0.5-1ml/kg/hr for first 15-30 mins

• Increase to 4-6ml/kg/hr thereafter

• Can be given as fast as possible in emergency situation

• Ideally within 4 hours

• Can slow down/take breaks if needed but ideally don't disconnect patient

How should you flush an IV in a blood transfusion?

Only with 0.9%NaCl as calcium containing fluids can form clots (interacts with anticoagulants)

What points should we note to do during a blood transfusion?

• Administer medications in a separate line

• Warming prior to admin not recommended (other than to room temp) → breakdown of RBCs in blood 

• Allow access to water but not food

What should you monitor in a patient receiving a blood transfusion?

• Monitor for signs of transfusion reaction during and after admin

• Monitor HR, RR & rectal temp (multiparameter machines)

• Watch for signs of anaphylaxis e.g. swelling, urticaria, nausea, vomiting

• Try and categorise to decide on underlying cause/appropriate tx

What are the types of transfusion reactions?

• Haemolytic

• Respiratory

• Non-haemolytic

What are the different types of haemolytic transfusion reactions?

• Acute

• Delayed

What are the signs of an acute haemolytic transfusion reaction? What should we do?

• Happens in minutes

• Severe

• Tachycardia/tachypnoea

• Nausea/vomiting/pyrexia

• Haemolysed serum

• Haemoglobinuria

• Can result in death

• (expected with incompatible crossmatch)

STOP TRANSFUSION

What are the signs of a delayed haemolytic transfusion reaction?

• Happens over days 

• Mild(er)

• Slow removal of red blood cells

• Mild antibody reaction OR new antibody formation

• Jaundice/bilirubinaemia(uria)

• Slower reduction in PCV

What are the types of respiratory trasnfusion reaction? When does each happen?

• Transfusion associated circulatory overload (TACO)

  • Volume overload

  • Cats/small dogs/cardiac disease/renal disease

• Transfusion associated reaction acute lung injury (TRALI)

  • Immune reaction

What should be done in a case of respiratory transfusion reaction?

• Stop transfusion

• Oxygen Support

• Radiographs

• Judicious fluids

• ?furosemide?

What are the types of non-haemolytic transfusion reactions?

• Pyrexia/anaphylaxis

• Citrate toxicity

• Sepsis

What are the signs of pyrexia/anaphylaxis due to transfusion? What should be done?

• Wbc/proteins/ microparticles

• Vomiting/Nausea

• Panting/pyrexia/tachycardia

• Pause transfusion

• Slower rate

• Chlorphenamine

• Maropitant

What are the signs of citrate activity due to transfusion reaction? What should you do?

• Shaking/shivering

• Check iCa2+

• Administer calcium on separate line

What should you do if you can't differentiate between a mild transfusion reaction or stress/underlying condition?

If in doubt, 15-30 minute break, restart at slower rate

How much is the reccommended rate of fresh frozen plasma/frozen plasma or Cryo?

10-20ml/kg