Hi, my name's Sophie McMurra. I'm a registered veterinary nurse and a veterinary technician specialist or VTS in small animal internal medicine. I work at North West Veterinary Specialists, where I'm the internal medicine nurse, and I also have the social media platform, veterinary nurse, Medicine Geek for all of you who do like social media and internal medicine.
And I have the pleasure of speaking to you today about transfusion medicine and transfusion triggers is more important. There are many different products available on the market for dogs, less so for cats. And blood transfusions or blood products can be a life saving therapy.
We use them most commonly for anaemia, coagulopathies, or haemorrhage, plus a few other reasons. But just because we can, is it always the correct choice to transfuse? And I'm gonna talk to you today about assessing a holistic approach to each patient as they present, looking at the patient or the individual rather than just figures.
And looking at the pros and cons and why we should transfuse and why we need to look at the picture as a whole before jumping into a transfusion. And as nurses, we can minimise the risks because these, these are not benign procedures. Some things can go wrong and complications can occur.
But with careful donor selection, understanding the blood types, the testing that we need to do, and the monitoring that we can perform, we can minimise those risks to the patient. So let's start this with a systematic approach. So a patient has presented to you in the clinic.
It's an anaemic patient. We're gonna do a full TPR and see what clinical findings we can come across. So the patient has pale mucous membranes, of course, because it's anaemic.
It's tachycardic and tachypneic, and the reason they show those signs is because your red blood cells, which have now decreased, are responsible for carrying your oxygen. So the red blood cells have the oxygen carrying capacity and we now have a reduced volume. So our body needs to increase our respiratory rate in order to bring in more oxygen, and we also need to increase our heart rate so that we can perfuse the smaller number that we have that bit quicker.
So that's why you'll see a tachycardia and a tachypnea. We may also, when assessing pulse quality, providing the patient is compensating well, you may feel bounding pulses. And quite often people think, well, it's anaemic, it has a reduced blood volume.
So why would you have bounding pulses? But actually you have a reduced red blood cell count, but you don't necessarily have a reduced circulating volume. So the body is very smart and if you reduce your number of circulating red blood cells, it will go into a fluid retentive state.
So it will start to withhold, start to hold on to more sodium and therefore more water because we need to perfuse those cells that bit faster and more effectively. So actually, your circulate your circulatory system is a little bit more. At risk of circulatory overload if we give fluid therapy, for example, because it is retaining that sodium and that, that water.
And that's simply just to make sure perfusion is not affected. If the patient comes in and they're not compensating very well, well, maybe they've been in an acute anaemia and the body hasn't had time to compensate or it's been compensating for some time and it's just tipping over into the more critical stage, then you may feel weak pulses at that point. They may be jaundice and often an anaemic patient with hemolysis, they're often some of the most jaundiced patients that you will see.
They almost look like they're fluorescent and they will glow in the dark because they're so jaundice. And the reason for that is because haemoglobin is carried in our red blood cells. As the red blood cells are hemolyzed or destroyed, it releases the haemoglobin into the bloodstream.
It goes around the bloodstream to the liver where it's converted into bilirubin. And it's then excreted out. But if that level of hemolysis, the body can deal with a minor amount of hemolysis on a daily basis, but with the amount of hemolysis we see with an acute anaemia, it becomes very overwhelming and the body just can't convert the haemoglobin into bilirubin at the rate in which it's being asked to.
So they become very jaundice. They also become weak and they even collapse, and they often can't keep up with the same exercise demand simply because they just don't have that oxygen carrying capacity that they usually would. So anything that exerts energy or requires them to even go out for a walk, they may start to become weak and they could collapse because they just can't keep up with that same oxygen demand.
And we can often see a low grade heart murmur, maybe a grade 1. It doesn't often go over a grade 1, say maybe 2 maximum, but that is just because of the change in viscosity in the blood. So it's gone from the normal viscosity that the patient is used to, to a very thin, thin viscosity because it's just hemolyzed and there's hardly any red blood cells in there.
And often once we treat the anaemia, the heart murmur will also resolve as well. So with all of these clinical signs in mind, let's look at what we can do in the nursing considerations that we can implement to our patients. So quite often in the emergency setting, people think, oh, respiratory patient pop them on oxygen, but we don't always consider an anaemic patient as one who requires oxygen.
But actually they would really benefit from flow by oxygen, because we've just mentioned that our red blood cells carry our oxygen. So if we can saturate them to 100, we're giving the patient the best chance that it can possibly have in this current situation. So provide oxygen via a mask.
If you link up your pulse oximeter, I just wanted to put this in to make you aware of the limitations of what you may see on the screen. So if you're providing oxygen, hopefully that patient will be saturating at 100%. That pulse oximeter will look at the saturation of each individual cell.
It will not tell you whether you have any hypoxic episodes going on. So just because your pulse oximeter is reading at 100 doesn't mean that you are not having hypoxic episodes anywhere else in the body. And one of the places where it may indicate is on your ECG.
So if you link up an ECG to severely anaemic patient, quite often you can see a lot of abnormal complexes on the ECG and the reason for that is because of areas of hypoxia to the myocardium itself. So if this patient's PCV and oxygen carrying capacity has gone from 35 down to 6, that is huge. And we're relying on now 6% of this patient's PCV to still confuse that same amount and that same volume of tissues, and that's quite unlikely to happen without areas of hypoxia.
So the myocardium of cardiac muscle itself may throw out a load of abnormal complexes and it's because of the areas of hypoxia all over the myocardium. So they're coming from different areas, different aspects, which is why you're at your ECG can look very abnormal with a, a big variety of abnormalities. If you link up your blood pressure, providing the patient is compensating, they are likely to have a good blood pressure because the body is in that state of shock and it's retaining its sodium and its perfusion.
We need to correct the, the, this abnormality with blood, ideally, or fluid resuscitation, depending what the patient is presenting in for. And I would always avoid jugular samples in any anaemic patient because we don't know if this is originating from the platelets or if the platelets are involved. So if we are not sure, just super careful handling, these patients can have spontaneous bleeding.
And even just raising the vein, I've seen a patient have a thumb mark bruised just from raising the vein, and that was a patient with immune-mediated thrombocytopenia, which just means that its immune system was attacking its thrombocytes, which are its platelets, which are responsible for primary coagulation. So this has a has a clotting disorder. So if you're unsure at all and an anaemic patient comes in, stick with peripheral until we know otherwise.
And then sometimes patients can be hypothermic from this change in, in the, the viscosity. We know that our blood, is responsible for things like thermoregulation and sometimes this can cause them to struggle to thermoregulate. So patients can present in many different ways and many different reasons can trigger the requirements of a blood transfusion.
And a common question that we often get asked is, what is your number, your cut off of your PCV, for example, to say this patient at this number requires a transfusion. But it's not quite as simple as that. We need to look at the individual patient and what we call transfusion triggers to assess the individual.
So first of all, look at the, is it a chronic anaemia or is it an acute onset? So chronic meaning more than 3 weeks, has the patient had a month or more to compensate with this gradual reduction in PCV or in red blood cells until it's now got to a point where the owners presented it to the clinic? In which case the body has had a long time to compensate and make up for that lack of oxygen carrying red blood cells.
Or is it really, really acute in onset? So did this start yesterday? Did this start two days ago and it's acutely healla like an IMHA for example.
And now the patient's dropped suddenly, 20% of it, it's circulating red blood cells within 2 days. So the body's not had a great time and a, a great amount of time to respond to that. And often you will be able to tell whether a patient has had a chronic anaemia over acute simply by how they present.
So they can have the same number, so say a PCD of 10%. But one is coping really well and the other is on death's door. So that gives you a good indication as to the the rate of onset.
And often cats cope a lot better than dogs at the lower PCV. I've seen many cats with a PCV of 6%, whereas dogs start to get to around 10% and they are looking really, really bad. And that's probably just because a dog's PCV sits naturally that bit higher.
So for them to get to 6%, it's a much greater drop that they have rather than a smaller number for a cat. Also look at the rate of ongoing losses. So has this patient just been hit by a car and we're actually requiring a transfusion because of a really bad haemorrhage?
Is the patient still bleeding? Can we get to surgery and stop it now, or is it stopped in time for it to present to the clinic? Or is this a hemolysis and we're not sure what's going on, so we can't yet start treatment.
So it's not likely to stop just yet until we've had a chance to do some procedures and get some results back. And one way of looking at tissue perfusion, so whether the, the, the tissues are actually being perfused as well as oxygenated, is your lactate level. So, our bodies are aerobic, which means that they require oxygen to live.
All of our cells in our body require oxygen. If we can't get that oxygen delivery, then they are very smart and convert into an anaerobic state, which means that they don't require oxygen. They can't survive on this for very long, but it's a coping mechanism to allow the body to To adjust to the change in oxygen perfusion.
So it prevents cellular death, basically, so that the patients don't just drop dead as soon as you get any hypoxia. So in order to convert into an anaerobic state. There is a cascade of events which occurs, and the release of lactic acid is part of that cascade.
There's probably about 14 or 15 different things that need to happen in order to convert your body to an anaerobic state. So the release of lactic acid tells us that there is a tissue perfusion or an oxygen delivery problem. And that can be anything from an anaemia because of the oxygen carrying red blood cells are reduced, so it's just not able to keep up that same volume of oxygen delivery.
Maybe the patient's dehydrated and although the oxygen levels are absolutely fine, the perfusion is reduced because they're dehydrated. Maybe there's heart failure, maybe there's haemorrhage, there's many different things, you know, with thrombus, or GDV many different reasons which can cause an increase in your lactate. And the, the really important thing about lactates is you can use it to spot trends.
So yes, a patient could come in with a high lactate, but how is it responding to therapy? Is our is our therapy helping improve this patient's perfusion and therefore reducing the lactate? So it's a very useful bedside too.
And then look at the on the rate of ongoing treatment. So does this patient require an anaesthetic or surgery? If so, we need those oxygen carrying cells, so therefore it may require blood.
And what is the patient like? So is this a 14 year old dog with diabetes and chronic kidney disease? Is it a really elderly 18-year-old cat with hyperthyroidism, CKD, and a multitude of other problems going on?
If the patient has comorbidities and other diseases going on, what is a transfusion going to do? Will it help? Because sometimes it might, but not always.
And we need to assess the entire patient rather than just jumping in and saying, OK, well, let's give this a transfusion. Actually, what are we likely to be left with at the end? Will this patient survive and what is their mortality rate?
So I think this gives you a bit of a an overview about treating the individual and assessing so many different things rather than just what is the number of PCV that we transfuse because there's just much more to it than that, if it, it's just not that simple. So blood results, of course, have to come into it, but clinical signs as well as treating the individual is really, really important and a really important aspect of that holistic approach to each patient. OK, so now we need to get some blood work on this patient.
So a PCV in total protein is probably the first thing that we're going to consider. So if you look at your PCV or your pack cell volume, if you have a low PCV with a normal total protein, that indicates hemolysis. So your proteins are absolutely fine, but your PCV has reduced, which means that it's just the red blood cells which have reduced, and it may indicate that there is some destruction of the red blood cells there.
Whereas if you have a low PCV with a low total protein, it indicates that there may be a haemorrhage. So you're not just losing the PCV you're losing the proteins as well. So both products are being lost.
And of course, with any anaemia or any, any issue with the red blood cells, we need to look at the haematology. And with any haematology, we always need to do a fresh blood smear. Even if you don't look at it yourself in-house, then you can send it off.
And if it's fresh, it gives you an indication as to what the red blood cells or what all of the cells are looking like in the bloodstream at that time, rather than popping it into an EDTA tube and the lab making a smear 24 hours later, you could then get some alterations. An insaline agglutination test super easy and common that we can do in practise, and there's an image of one here. So this is a positive insaline glutination test, and you can see the red blood cells on the slide and you can see that it's clumped or what we call a sandstorm effect, and this means that it is positive for agglutination.
We can also do a Coombs test which would need to be sent off to the external lab, but all of these things do make a part of the diagnostic process of the likes of your immune mediated hemolytic anemias and IMHA. So they're all things that we should be considering in these patients. Coagulation panel.
So look at, there's a few different things that we can look at when it comes to coagulation. So your primary coagulation are your platelets. So your platelets become activated in the event of an injury.
They then almost become sticky and adhese to each other to form that platelet plug. And then your coagulation kicks in. So the coagulation factors which are made in the liver, will then kick in and they will come to the site as well to just stabilise that thrombus and stabilise the clot so that the patient doesn't bleed.
So that's primary and secondary coagulation. So you can look at your coagulation panels, which is usually your PT and APTT. You can get small handheld devices, which is a a bedside test that you can get in practise.
So they're always really useful. And then if your practise is lucky enough to have thromboelastography, also known as a tag, this looks at the pattern in which almost the behaviour of the platelets. So are they clotting and then are they breaking down as well.
So it will give you a set kind of image as to what's going on with that coagulation cascade. And if there are any any issues like it's You know, there's delayed clotting or it's hypercoagulable or it's not breaking down or it's breaking down too soon, this gives you an indication as to what can happen. So it can be really useful to tell us about how the patient's coagulation process is happening.
Angiostroullu, so always really useful because you can become, you can get a coagulopathy off the back of lung worm or angiostronggulus. And then of course we need to do a biochemistry, so we need to check for concurrent diseases. So what's actually causing this?
Is the patient's liver or kidneys OK? Look at the whole picture. And then your analysis is the bilirubin present.
What, what are the proteins looking like is the hematuria. And then of course depending on the patient, you could start to consider any infectious diseases for mycoplasma hemophilus in your cats, Borrelia. There are a multitude of different infectious diseases being brought from abroad as well.
So there are many different infectious diseases that we can certainly consider running. So as nurses, I'm gonna tell you how to do a few of these tests, and I think. There are many things that we don't always do, but that we can start to do.
And even if you think, oh well, I couldn't do that, such as looking at cytology and the different things that we can analyse under the microscope. I would encourage you to just start looking at the norm. And if you get used to what the normal looks like, you will very quickly be able to spot when things are abnormal because you'll just get used to seeing a normal blood smear.
Well, first of all, let's start with the insaline agglutination test. And if any of you are my age, you will remember that we used to say one drop of EDTA blood with one drop of saline, and it does have to be saline. But now the most recent consensus statement from 2019 said the four drops of saline is actually much better.
So it's much more accurate and much more likely to give you a yes or no answer. So, 1 drop of blood, 4 drops of saline, mix it about and then you will get this sandstorm effect which I mentioned earlier. So this is what we call macro agglutination, we know that we can see the agglutination with the naked eye.
But just because we don't see it with the naked eye, it doesn't mean that a glutination is not there. So it's really important to then pop this under the microscope or do a blood smear and pop that under the microscope to then see what we can what we can see going on with those red blood cells. And I do have a picture of the agglutination which I'll show you in a moment.
The other things that we need to consider are a platelet count, which we can absolutely do as nurses, and I'll show you how in a moment. Look at regeneration, so is this a regenerative anaemia or a non-regenerative anaemia? And just by defining into one of those categories, rules out a load of differential diagnostic, issues.
So it just allows us to narrow our field to say actually this, this, these are now our differentials because it's regenerative or it's not regenerative. And I'll also show you how to do that. Assess for a glutination, as we've just mentioned, and I just wanted to put on there about roo formation.
So roo formation can look quite similar to a glutination, but it's almost like the stacking of red blood cells. This can be normal in a cat, but it's not normal in the dog. So if you Look at a blood smear.
They should all be. If you look on the monolayer where it's just one layer of blood, none of them should really be touching each other. They're usually nice and spread out.
A glutination, you will get clus altogether, whereas roo look like they're almost a string, so stacking of coins, and that's how to tell the difference. And then you can also look to see for, see if there's spherocytosis, so don't be put off by a big fancy word. All that means is that the red blood cells, rather than having that biking cave disc shape, they are now spherical.
And that is also part of the diagnostic pathway for IMHA. So rather than having that Viking cave disc with an almost a very mild central pallor, they just look like footballs and they don't have that middle disc shape anymore, and I'll show you that in more depth in a moment. So you can see this image here.
So let's assess for regeneration. So the easiest way to do this is to find, look at the blue arrows, so find the biggest cell and find the smallest cell. So you can see there's quite a big variation there between those two cell sizes, and that indicates that there is regeneration.
So those red blood cells are different ages. And actually those bigger ones are your immature red blood cells and they get smaller over time. So if you had a non-regenerative anaemia, they would all look a very similar size, and there wouldn't be big ones and small ones.
They would all be, if you try to look for the biggest and the smallest, they'd kind of all be a similar size, whereas this one shows that there is regeneration there, which tells us that our bone marrow is regenerating red blood cells. So this could be a regenerative anaemia. And then platelet counts, so look at your red arrows.
So platelets are. Kind of fragments of a cell. So we have our bone marrow, which throws out a mega carrier site.
This then buds off into platelets. So they are not uniform in size. You can just see they are kind of little purple dots in between the red blood cells.
And what you would do, well, I'll tell you what you would do in a moment, but you would look for all of these, platelets on each field to see whether the patient has platelets or whether there is a reduced count. And then the black arrows are your spherrocytes. So look at, you can see that biking cave disc with almost the central pallor on some of the normal red blood cells, but the black arrows are pointing towards what we call spherocytes.
And these just mean that they are spherical and they've lost that central parlour. And the reason they go like they turn into these is I just like to think of it as as hemolysis occurs, the body attacks the red blood cells, they almost pop and don't have that biking cave disc anymore, so they just become spherical, and that is a good indication of IMHA. So platelet counts are absolutely something that we can do as RVNs.
I do it quite commonly in practise, and it's a really good skill to have. So at the start, we need to look at the feathered edge, and we want to see if there's any platelet clumping because this can be very useful if you do get a reduced number of platelets in your monolayer. You know that it's a genuine reduction in plate in thrombocytes or platelets.
Whereas if you have maybe taken the blood smear, there's been a bit of a delay between you taking the blood and getting the smear done, or the blood maybe hasn't flowed properly. It's been taken from an IV cannula where it's, you know, not being taken straight away. Activation of those platelets can occur very quickly and if that's the case, you will have them starting to accumulate and starting to lump in the feathered edge.
So if you do see a reduced platelet count in your on your field, you need to look to see, oh actually there's loads of them all clumped together in the feathered edge, or no, the feathered edge is clear, so this is a genuine thrombocytopenia, if that makes sense. So once you've looked at the feathered edge, go down to the monolayer, which just means where it's one cell layer thick. So you're not at the base where it's really thick, where the smears started and not at the feathered edge, just the way you can see one layer, and they shouldn't be overlapping each other.
So we need to look at 10 different fields under the oil immersion on the 100 lens. Count the platelets on each field, Count, write them all down, and then work out the average number between all 10 fields. Each platelet represents 15 platelets in the circulation.
So we need to. I get, I think this is on the next slide, so let me skip across. So if you do your number of average platelets, say you have 15 per high powered field on average, times it by 15, see what your number is.
And you'll see here that the normal platelet count is between, depends on what textbook you read, between 200 and 500, and the units are times 10 to the power of 9 per litre. So between 200 and 500 is normal. If you have thrombocytopenia, primary thrombocytopenia, your platelets can go down to less than 10 to 20.
So absolutely huge reduction from 200 to 500. But there's minimal risk of spontaneous haemorrhage until you get below 30. So this is why with IMTP patients, you are likely to see spontaneous bleeding because of such a big reduction in platelet numbers.
So this is your, an example of the insaline agglutination test. You can see those clumps here by the naked eye, and then on the right you can see what we call microevolutination. So rather than them having individual cells all spread out, you can see that they've actually clumped together, and that's what we call a lutination.
So that would be positive for a glutination. And it's really important to look at your blood smear because you can't always see it with the naked eye. So depending on the degree of a hallucination, you could assess it under the microscope and it be positive, whereas with the naked eye, it could look OK.
And then this is a halllutination on the left versus roo formation, so the stacking of coins on the right, and this is what we mentioned is normal in cats. And I will also just mention that you can see that some of those cells are just slightly spiky. That's called crenation, and often it can occur if the blood smear just hasn't been dried fast enough when you've stained it, and that that doesn't really mean anything.
It's it's a normal thing to see. So now that we're dealing with this patient is suitable for a blood transfusion, we need to start looking at the other tests to perform, so blood typing. So there's many different in-house blood typing kits available.
They're super quick, super easy, and they're available for both dogs and cats. So with dogs, ideally, in the ideal world, with no money issues and no time restraints, we want to, blood type every single dog. We know that this is not always possible, and negative blood is a universal donor.
So providing it's the dog's first transfusion, you could be safe to give a negative transfusion to a negative or a positive dog. You can't do it the other way around. It's only negative.
That is safe to give to the others. Or if that patient has had a transfusion before, it could have built antibodies against that blood type. So it's absolutely vital that they then have a blood type performed and the appropriate blood type is given to them second time around.
But with cats, they absolutely 100% must be blood typed, cannot skip this step in a cat at all, and the reason for that is because they have naturally occurring aloe antibodies against the other blood types. So if you have a type A cat and you give type B blood, it already has those antibodies which will attack those red blood cells of the other blood type. So absolutely vital in the cat at all times.
So of course, dogs and cats have different blood types. So the cats have A, B, and AB. The most common being A, which makes up around 70% of the population, but 30% makes up type B, and it's common in some pedigrees like your British short hair.
And then AB is incredibly rare and only makes up around 2% of your population. So I've just mentioned about the naturally occurring alu antibodies with cats, so even just a couple of mLs could result in a fatal transfusion reaction in a cat, so it's absolutely vital to get this right. So they must only, not, not only must they have a blood typing, but they also need a cross matching.
The only time that you would skip cross matching is if the patient is dying in front of you and it really just needs that blood product or it will die. In any other circumstance, we should always crossmatch. And you may think, well, it's got the same blood type.
We don't really need to crossmatch, but cats. We just always do because we don't know what their blood is going to do and we'd much rather see a reaction in the tubes in front of us and think, oh, thank God, thank goodness we didn't go ahead with that, rather than when it's in the patient and the patient's now starting to die because of a severe reaction. And just to give you another indication as to why it's really important to crossmatch is the more recent discovery of the MC antigen.
So this is a new feline blood group antigen, and you can be negative or MIC positive. And if you were to transfuse a patient with this. There's limited data available, but we know that they can have more severe reactions, and we can't yet test for this.
We can, you can send off and see if they have a antigen, but by that point, the patient, you know, usually this is more of an emergency situation. So your blood type and cross matching lets us know whether they're likely to have a reaction rather than testing for the antigen. So, Cross-matching, absolutely vital in cats at all times.
And then when it comes to dogs, we have DEA 1.1, 1.2, and 3 to 8, but we commonly just talk about 1.1.
Acute transfusion reactions are more rare in dogs, they're a lot more safer to give transfusions to. We need to take caution if the patient is currently pregnant, we used to say if they have had a pregnancy, but now we say if they are pregnant or if they've had a a previous transfusion in the past. The negative blood type is a universal donor, so you can give negative to positive, you cannot give positive to negative.
And again, just like the mic antigen in cats, the dogs have what we call a dull antigen. Dalmatians have a high frequency of the dal antigen, hence the name. So they're much more likely to experience transfusion reactions, although it's not widely studied.
So again, we have limited data, and this is where cross-matching comes in to let us know we are that bit safer and we can then confidently transfuse without, with a minimal risk of a transfusion reaction. So cross matching is absolutely vital. I'm gonna show you some pictures of what cross matching looks like.
And it's basically where you get the donor blood and you mix it with the recipient blood to identify whether they are compatible or not. You can have a life threatening reaction or a transfusion failure if you go ahead without, and dogs do not have naturally occurring aloantibodies, so this would only really be necessary if it were to have a transfusion previously. So when you're cross matching for the dog products, if you buying these products, these pigtails are really useful to, for your cross matching and blood typing so that you don't have to broach the bag.
So what I would do, snip one off, withdraw the whole lot and then mix it in your syringe. They're actually really tricky to mix in these kind of crimped given sections. So withdraw the whole lot out and then mix it well in the syringe.
You can then do your PCV and everything from that. And remember that if you do have a large breed dog and you need multiple units, you must cross match. If it's a patient who requires cross matching, you must cross match each unit because they are different blood products from different patients.
So just because you've cross-matched one doesn't mean that the next one is then safe. So this is an example of a cross-matching kit and the end result that you end up with. Apologies, my camera is now blocking the one of the tubes.
But basically you have your donor blood in the middle, and you have an example of a positive reaction on the left and on the right, you have an example of a negative reaction. So we then look at the donor blood to see which one it it matches. So you can see the blood is at the bottom and it react it's compatible with the negative reaction, which means that it's not has a reaction and you should be safe to transfuse this blood.
If you were to get a positive reaction, that means that the patient is highly likely to have a reaction to this blood product, and we would not go ahead at that stage. You tend to start off with about 9 different tubes, and this is just the the end result of what you end up with. So the different products that we have available for dogs, we're actually really, really lucky here in the UK because we have the pelo bank and they will make specific products.
So that we can use them for what that individual requires. So not every patient requires whole blood. So that's the the plasma with all of the red blood cells.
You can get fresh frozen plasma and platelet rich plasma, and there are different products available. Sadly, we don't have the same in cats, but we are lucky with, with dogs and how we can tailor our approach to the different products that we have available. So for dogs, we have whole blood and for cats as well, but then the rest only apply to the dogs in this country.
So pack our blood cells, fresh frozen plasma, cryoprecipitate, which is good for your von Willebrand's patients. We will often get these in for our Dobermans who are coming in for wobbler surgery. If they have von Willebrand's disease, then we will transfuse them with cryoprecipitate before the procedure.
We also have platelet rich plasma for thrombocytopenia, which is not immune mediated. And then we have human albumin which I seem to remember was used much more commonly a while back and it seems to have fallen out of favour, but it is still available. And then for our feline friends, we are much more restricted, so we sadly don't have a feline blood bank in the UK for cats.
Our red blood cell storage time is limited, so it can be 24 hours in the fridge or 35 days if you use the closed method, which is actually really difficult to do. So quite often we will use the open method, which means it has to be discarded after 24 hours. It's very difficult to find a suitable donor in the time that you require it.
And quite often if you speak to many different practises, we will all be saying the same thing that's actually really difficult to maintain a donor list and have a donor that is readily available. Quite often we use a lot of staff staff pets because they're the ones who we can rely on most commonly. So let's look first of all at whole blood.
I'm not gonna talk you through all of the different products, but whole Blood is one that we would use for dogs and for cats. It must be given with a hemic philtre. I would use that for all of the products.
We, it is a replacement therapy, so it is the plasma, it is the red blood cells. It's a direct replacement of what the patient has lost if it's whole blood that they are requiring. Calcium containing fluids, calcium and glu or glucose containing fluids must never be administered alongside a blood product.
And the reason for that is because the anticoagulant collates calcium in order to stop the coagulation cascade. So if we go and give a calcium containing fluid alongside, we're overwhelming the the citrate's ability to act as an anticoagulant and small thrombus could occur. So sodium chloride is good or plasmali is also good because they don't contain glucose or calcium.
And then Echocardiogram to rule out cardiac disease in cats prior to donation, I've put on here because I'm not gonna talk to you about the different donor requirements because that is readily available online and you would have to bring it up each time you do a react a donation anyway. But echocardiogram is something that's a little bit more new on the list. And I think this is useful for patients who, if you are putting them on a donor list, it's useful to do maybe annually.
And the reason for that is because only 30% of cats with cardiac disease have a murmur. So if you do an echocardiogram, you can still pick up cardiac disease in patients who don't have a murmur. And if you were to take 20% of the circulating blood volume from a cat in heart failure or with heart disease, it could be enough to tip them into failure.
So it just allows you to rule out, cardiac disease and make it that bit more safe for the patient. A lot of clinicians will say, well, we don't have time for an echo because it's an emergency, so they will be happy with no murmur, no gallop rhythm, and no arrhythmias, and they would then say, OK, we need to have that discussion with the owner that we can't be absolutely certain that there is no underlying cardiac disease, but we're happy to proceed on these this basis. So it's something to bear in mind.
And then we have packed red blood cells, which is just the red blood cells with anticoagulants, so there's no plasma in there. So this is good for patients who just need those red blood cells like the IMHA or any anaemic patients, and quite often they are normovolemic, they just need the actual red blood cells and the plasma's fine. They don't contain any clotting factors or platelets, and they are viable for up to 42 days in the fridge, so really useful.
So when it comes to the donor, what we need to remember is that they can't consent to this. So it can be quite a negative experience for even the most pleasant and well-behaved and calm cats. So I'm a big advocate for sedating these patients every time.
I would even say the same for a dog, even if it's, you know, maybe a very mild sedation, maybe a bit of borphannol or something, just to take the edge off, but I think a cat needs to be fully sedated. To expect them to sit still for around 20 minutes with a sharp needle in their neck is probably unrealistic, and 2, it's just not very ethical. So I would always date or GA.
It will minimise the risks of complications. So if they're not moving, they're not causing a hematoma, then also not stressed as well. It will minimise the likes of your stress hyperglycemia.
And actually, many studies have shown that there are adverse reactions when the patients are conscious, such as open mouth breathing, tachycardia, tachypnea, and the hematoma formation. It's a much more positive experience for the patient, but also for us, for the vet team. And it also improves owner satisfaction because they have a nice calm patient who's going home, not a patient who's open mouth breathing and looking really stressed.
So when it comes to calculating the volume of blood to take from a dog or a cat, they do differ slightly. So a dog's full circulating blood volume, we estimate to be between 70 and 90 mL per kilo, whereas with a cat, we say around 50 to 60 mL per kilo. And you can take up to 18 to 20% of their circulating blood volume at any one time, which works out around 10 to 12 mL per kilo.
So for a dog, around 30 kg, they need to be, sorry, above 30 kg to donate a full unit. A full unit of blood is 500 mLs in a dog, and their PCB ideally should be above 40%. And with a cat, you want them to be above 4.5 kg to donate a full unit, which is 50 mLs, and ideally we want them to have a PCV of around 35%.
So for the dog, I've taken this calculation from the pelo bank and it's a little bit more long-winded for the dog than the calculation I use for cats. But it is still a formula. You just follow the formula, input your information, and it's actually quite simple.
So this is a screenshot of the the calculation that they use. So 2 mLs of transfused whole blood per kilo. Raises the PCB by 1%, whereas if you're using pacta blood cells, it's much more concentrated with red blood cells.
So 1 mL of pacttra blood cells per kilo will raise the recipient's PCB by 1%. So you need double the volume of whole blood because it's, it's got both plasma and red blood cells, whereas the packed red blood cells are concentrated just with red blood cells in anticoagulant. OK, so let's do this calculation.
So you have a 10 kg dog with a PCV of 10%. The target PCV is 25%, and remember, you don't need to give them a target PCV within the normal range, because that would be a huge volume that you're going to transfuse. You just need to get them into a safety zone.
So a dog with a PCV of 25% would be in a much more stable condition than a dog with a PCV of 10%. So target PCV of 25% minus the recipient's PCV of 10%, times by 10 kg, times by 90, which is the figure given by the Peplo Bank for dogs. Devised by the donor PCV, which usually is 62% in impact red blood cells.
And that gives you 217 mL, so that's how much we would transfuse to a 10 kg dog. So, a little bit more long-winded, but it's a formula, so it is actually quite easy, you just need to input your details. I find the cat much more straightforward.
So we've just said that a cat's circulating blood volume is 50 to 60 mL per kilo, and we want to remove a maximum of around 18 to 20% of that, which comes to 10 to 12 mL per kilo. So let's put that into practise. Say we have a donor cat of 5 kg, and that needs to be a lean body weight.
So this patient has a bodily condition score of 5 out of 9. They can't be above, they can't be 4.5 kg, but they're overweight because actually their lean body weight would be less than that.
So ideally we want 4.5 or above, but to keep the math simple, let's do 5 kg. So his circulating blood volume, estimated at 50 to 60 mL per kilo, works out at 50 mL.
50 mLs times the 5 kg is 250 mL of circulating blood volume. So if we want to withdraw 10 to 12 mL per kilo of that, that comes to 50 mLs to withdraw. But then we also need to bear in mind the anticoagulants.
So if you're taking this out of the patient into 20 mil syringes, which is what I like to do, 1 mL of anticoagulant per 7 mLs of whole blood, and we use citrate or CPDA anticoagulant. So if you're using 20 mL syringes, if you fill in that whole 20 mL syringe, you want 2.85 mLs of anticoagulants per 20 mil syringe.
So you need to take that into account because if we just say, well, we're taking 50 mLs, well, 7 mLs of that will be anticoagulants. So actually we need to calculate how much blood we're taking, how much anticoagulant, and then the total volume in that syringe would be, in this case, 57 mLs. So when we administer it needs to be warm to room temperature.
The beauty about taking using the cloak the open method with cats, if you take multiple 20 mL syringes, you can leave some in the fridge. You can take one out, pop it on your syringe driver, and then the others are remaining fresh in the fridge. Once they hit room temperature, they should be used within 4 hours because it has been shown that after 4 hours, you're a much greater risk of having contamination of that blood product.
When you warm the product, just do it in your hand, ideally. Overheating can cause a glutination of the red blood cells, and that makes the whole thing completely pointless. Again, you can always use a blood philtre and I would have it the closest to the patient as possible.
So if you're using a T connector on the leg, pop it straight on there. So you don't want it right kind of near the start of the given set when there's a lot of things that could happen during that whole the given set and the extension T connector. You want it as close to the patient as possible to make sure that you're filtering out anything just before it enters the patient's vessel.
I put here to have caution with infusion pumps, and the reason for that is because previously they've looked at red blood cells prior to going through an infusion pump, and then after going through the pump and there was a glutination, well there was hemolysis of those red blood cells. However, now we're quite lucky that technology has moved on and the brawn and the infusion. With 2 of 3, I can't remember the 3rd 1, but they've tested those drip pumps and they did not damage the red blood cells at all.
And we've mentioned about not using calcium and glucose containing fluids because it overwhelms the the collating ability of the rate. And then I can't really conclude this talk without mentioning xenotransfusions. So a xenotransfusion is when you give a blood product of a different species.
So in this instance, I'm, I'm talking about giving dog blood to a cat. This should be used as a last option. It should not be your go to.
It should be if the patient has had a previous reaction to a blood product in the past. You don't have a donor available or not available within the time that the patient is, requiring blood. So maybe if it is a genuine emergency and you just can't get access to a donor.
If there's money restraints, so the owner can't pay for a donation and all the things that come along with that, but they can afford a bag of blood, or if it's a genuine emergency and you really just cannot wait. It is a it is aimed for short term stabilisation. So they are likely to have a reaction, but it may be a delayed reaction by the time they build the antibodies against the, the blood product.
You want to give a minimal volume, so you don't need to give a huge volume of this. You just want to get them out of the woods and out of that danger zone just to stabilise them. So you can maybe give a smaller volume of this than you would of blood from the same species.
And it is one use only once they've had a xenotransfusion, a second one is almost certainly going to kill them because they will have antibodies against it the second time around, so single use only. And if you would like to look up the pros and cons of xenotransfusion, then there is, I have referenced a paper here, a retrospective study of canine blood xenotranfu xenot transfusions, published in an open access journal by the ICACA. So have a, have a look, have a read.
It certainly has its place and it has its benefits, but I think we all need to be Very aware of the limitations that we should practise. OK, so monitoring for giving this transfusion. So I've created and actually there's a on the consensus statement of feline blood transfusions, there is a really good monitoring sheet so that you can use with prompts on there to say PCV beforehand, PCV afterwards, you know, all of the the different monitoring that you should be given and also the The dosage that you should be given and how when to change it for for a transfusion.
Rate. So really useful. But if a, if a reaction is going to occur, typically it's within the 1st 15 to 30 minutes.
So we want to get, before starting any transfusion, we want to get a baseline TPR temperature, pulse, respiratory rate, ideally blood pressure, have a multi-parameter on that patient if they are quite poorly, then usually they will tolerate ECG pads on, or clips. Blood pressure cuff. You can even pop the rectal thermometer in there and then it's all on the screen.
You don't have to keep going in and interfering with the patients every 5 minutes. So immediately before the transfusion can't be done from 8 o'clock this morning. We want it now so that we can instantly notice any dramatic changes if they're likely to have a reaction.
We want a constant observation for 15 minutes along with TPRs every 5 minutes to see if signs of transfusion reaction is going to occur. And we want to start off this transfusion with 0.5 mL per kg per hour, just for the 1st 15 minutes to see what reaction they have.
Because if it is going to react, even just a mil in a cat could be fatal and could kill it. If you are using T connectors, just make sure you're priming the tea connector with this, with the blood products before, because if you do 0.5 mL per kg per hour, it hasn't even entered the patient before we go increasing the dose and deeming them as safe.
So prime the T connector first, and as you press go you know that that is going straight into the patient's vessel. If all is good, after 15 minutes, go up to 1 mL per kg per hour, so just double it again for another 15 minutes. And then if all OK, we want to increase and give the remaining, remaining dose over 4 hours.
We should be monitoring TPR every 15 minutes until we're past the hour mark, and then after that, we should go to hourly, ideally. And if the patient is really, really poorly, we can give it at a faster rate, but we should still do those test rates just to make sure they are not going to have a reaction, if it's all possible. And then at the end, we need to repeat the PCV.
So we used to do a lot of trying to predict the outcome and how much the PCB is going to increase. But actually, they're so inaccurate. And even on the consensus statement, it says that they are not very accurate at all.
So now we're kind of moving away from that and just doing a PCV before and a PCV after to see how it has improved. So when we look at reactions from transfusions, they're kind of categorised into two different categories. So we have immunological and non-immunological.
So one is from the patients from the immune system, and one is not. So immunological is caused by antibodies within the patient's red bloodstream against the recipient's red blood cells. So as those red blood cells go in, the body sees it as foreign material, it attacks it and it will cause a reaction and destroy those that transfusion.
It can have a very acute onset and will result in destruction of the entire transfused blood. So if you do see any signs that a reaction is occurring, stop immediately and I'll mention about the clinical signs in a moment. And then we have non-immunological, so this is typically caused by incorrect handling or storage of the product, or maybe somebody's warmed it up, put it into a warm water bath, which is fine as long as it's just lukewarm water.
It's too hot, you'll cause hemolysis. If you put it in the microwave, which I've seen people do, you'll cause hemolysis. If you've tried to warm it on a radiator, which I've also seen people do, you will cause hemolysis.
So those are all things that are likely to cause a reaction. It could also be due to the administration of store products to a patient with liver failure. So we know that ammonia is a waste product and those red blood cells are alive within that bag.
So as the patients, sorry, as the red blood cells are alive, they have aerobic anaerobic metabolism within that bag. Ammonia is produced as a waste product and it has nowhere to go. There's no kidneys and no liver to send it to anymore, it's just sat within the bag.
And actually, the IMHA consensus statement has shown that the patient may have an increased mortality rate if given a transfusion which is over 10 days old, simply because of that buildup of ammonia. Now that's not to say not to use a transfused or a product that's over 10 days old, but just be aware and if you have the option, certainly go for a a fresher, a a fresher product. And then volume overload as well.
So maybe the patient has cardiac issues or we've just given it that bit too fast. Maybe, you know, cats are more susceptible to volume overload. And also just any patients in a state of shock or Illness, they are, you know, they retain sodium and water much more, so they are at greater risk of fluid overload.
OK, so there's a lot of information there, but I hope you've taken some of it in, I hope it's not been too much. And I'd like to thank you very much for listening. I hope you've enjoyed it.
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