transfusion medicine

does my patient need a blood transfusion

No ‘magic’ cut-off and should be based on clinical signs

What we’re looking for: Signs suggestive of reduced oxygen provision to the tissues

Tachycardia, tachypnoea, lethargy, weakness etc.

Ensure patients are normovolaemic before deciding whether to transfuse

Typically, 10-15% range for cats and 15-20% range for dogs

which blood product should i use

As much as possible… replace ‘like with like’

Blood loss – Replace with whole blood or, if not available, packed red cells

Haemolysis – Replace with packed red cells

Coagulopathy – Replace with fresh frozen plasma, regular plasma, or cryoprecipitate depending on the cause

UK pet blood bank

Some practices will have their own blood donor program and will store whole blood (<21d)

Most practices will use the UK Pet Blood Bank

Provide all blood products as well as equipment required and guidance

Can deliver 24/7 - OOH cost depends on distances from Leicestershire (central depot)

Provide crossmatching service with IDEXX

No feline blood products

why blood type my patient

Knowing a patient’s blood type is important as this will influence the blood type of the blood product you administer

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

Not strictly necessary for administration of plasma products (FFP/FP/Cryo) - most are DEA 1 negative (naïve)

what blood type is my patient

Based on the Dog Erythrocyte Antigen (DEA) system

Many different types but the one we care most about is the DEA 1 blood type – most antigenic

Dogs do not have naturally occurring antibodies

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

Hence why in DOGS, the first transfusion is USUALLY ‘free’

However, will develop antibodies following exposure (transfusion)

Therefore, may have a transfusion reaction (i.e acute haemolytic

reaction) if exposed subsequently

pathophysiology - antigen/ antibody

antibodies = found in plasma

antigen = found in RBC (DEA in dogs; Type A or B in cats)

Pathophysiology: Antibody-Antigen Reaction

first transfusion - no reaction

second transfusion - 1 month later

what blood type is my patient - feline

Based on the A/B system with A being dominant over B and AB being polygenic

Cats have naturally-occurring auto-antibodies. Type B cats have high levels of natural anti-A antibodies

Therefore: Imperative to give TYPE-MATCHED blood to cats as can have fatal acute haemolytic reactions from as little as 1ml of incompatible blood

Giving non-type matched blood will result in a haemolytic reaction

Giving B cats type A blood is BAD – severe acute haemolytic reaction – can be fatal

Giving A cats type B blood is not As Bad – milder, delayed haemolytic reaction – still want to avoid

how can i blood type my patient

Gold standard is sending to an external laboratory for confirmation – rarely time to do so!

Otherwise using a cassette or card-based methods

Only available for DEA 1 and A/B

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

Important to scrutinise changes on card- based method

If auto-agglutination occurring (e.g. IMHA), must wash patient red cells before using card-based method

Consequently, cassette method is preferred

what is crossmatching

detects more haematological (type II HS) incompatibilities than blood typing alone

Blood typing will only detect DEA 1 and A/B, whereas crossmatching will detect the majority of antibody-antigen incompatibilities

Will not detect non-antibody mediated incompatibilities

Major crossmatch – Recipient antibodies against donor red cells

Minor crossmatch – Donor antibodies against recipient red cells

do i need to crossmatch my patient

It depends…

• If has had previous transfusion (blood) then it is imperative

• Unless within 3-5 days of the first transfusion

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

• Similarly unclear with previous pregnancies

how should i crossmatch my patient

Laboratory method is gold standard

Straightforward but time-consuming manually

Rarely get a 100% compatible donor (choose least risky)

IDEXX and Pet Blood Bank will crossmatch and deliver bags to you (takes ~24h)

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

how much should i give my patient

A ‘restrictive’ transfusion target (PCV 25%) is probably just as good as, if not better, than a ‘liberal’ transfusion (PCV 35-45%)

Conditions that can predispose to volume overload: Small size, heart & kidney disease, hypoproteinaemia

Animal that is anaemic from haemolysis will not tolerate the same volume replacement as an animal anaemic and volume depleted from haemorrhage

Use formulas as a rough guide:

• 1ml/kg pRBC increases PCV by 1%

• 2ml/kg whole blood increases PCV by 1%

round up to the nearest bag

Wide variation in post-transfusion PCV

how should i administer my blood product

Intravenous administration

Intra-osseous also acceptable

Transfusion reactions generally dose- dependent so all products administered at a slow rate initially, building up thereafter

Need to consider equipment available and ability to monitor the patient

Maintaining sterility is vital as blood is an excellent growth medium for bacteria

Must be given through a transfusion set with an in-line filter (210um)

In dogs, better to administer drip-by-drip through a transfusion set rather than through a fluid pump. If using a pump a cassette pump better than linear peristaltic

In cats, better to administer via a syringe driver

However, important to use the method that is safest for the situation/practice

how fast should i give my transfusion

0.5-1ml/kg/hr for first 15-30 mins

Increasing to 4-6ml/kg/hr thereafter

Can be given as fast as possible in an emergency situation. The faster the rate the greater the risk of damage to RBCs

Ideally within 4 hours but isn’t overly necessary

Can slow down/take breaks if needed but do not disconnect patient (ideally)

other points - what to flush with and why

Only flush IV with 0.9% NaCl as calcium containing fluids can form clots

Administer medications in separate line

Warming prior to administration is not recommended (other than to room temperature)

Allow access to water but not food

No set time for measuring PCV post transfusion

what should i monitor and why

Monitoring for signs of transfusion reactions during and after administration

Monitoring heart rate, respiratory rate, and rectal temperature

• Multiparameter machines - better

Watching for signs of anaphylaxis such as swelling, urticaria, nausea, vomiting etc.

Try and categorise to decide on underlying cause/appropriate treatment

haemolytic transfusion reactions

acute = happens in minutes = why start transfusions slowly

respiratory transfusion reactions

usually associated with volume overload

non-haemolytic transfusion reactions

transfusion reactions

Severe reactions obvious, however mild reactions difficult to tell if transfusion reaction/stress/underlying condition

Usually difficult to highlight a specific cause and often treat symptomatically

If in doubt, 15-30min break, re-start at a slower rate (do not disconnect patient)

Pre-medication does not affect incidence of transfusion reactions