Hello everyone, good evening and thank you for listening to my presentation. So this evening we're gonna talk about just an introduction to feline transfusion medicine. So just a little bit about what we're gonna cover this evening.
So we're gonna talk a little bit about the feline blood groups and then go through what the current situation is in the UK about how we provide transfusions to cats within the UK and if there's anything on the horizon for feline blood banking in the UK. We'll talk a little bit about various products that are available and when it's appropriate to use which products and then go into a few practical trick and tips and risks and complications of blood transfusions. So what are blood groups?
Well, we all know this, blood groups are essentially genetically determined antigenic markers on the surface of red blood cells. And these, antigens are, antigenic and form antibodies in recipients that lack the same marker. So, we all know there's 3 main blood groups in cats.
There's type A, and obviously type A cats will display the type A antigen on their red blood cell surface. Type B cats have the type B antigen on their red cell surface, and type AB caps will have a roughly equal amount of type A and type B antigens on their red blood cell surface. The the most common blood group in the UK is obviously type A cats, and that varies with geo geographical location.
And also with breed. So to date, all Siamese, Burmese, Tom and Bengal cats are identified to be type A. However, I would certainly recommend that you still blood group these cats prior to any blood transfusions.
And blood type B is much less common, but we see that more commonly in British shorthaired cats, vermins, Devonors rex cats, and then Abyssinian, Persian, and Somali cats as well. But ultimately, any cats can be Type A or type B, and it's very important to blood group cats, appropriately. And of course some cats can be type AB as well, but that's much less common.
So cats have naturally occurring alloe antibodies. So what this means is that a type A cat will have anti-B antibodies regardless of whether they've had a blood transfusion before. Type B cats will have high levels of anti-A antibodies, whereas type A cats will actually have a relatively low anti-B antibody type.
This is different from dogs. And in dogs, dogs don't have naturally occurring antibodies against the opposite blood group. Now interestingly, type B cats obviously do not have any allo antibodies because of course if they did, they would react against themselves.
So this means that in cats, it's really important to do blood grouping prior to first transfusions because AB mismatched transfusions can lead to life-threatening hemolytic transfusion reactions without cats having received a transfusion before. It's absolutely imperative that cats receive blood from a donor of an appropriate group, which is really obvious with type A cats. You give them type A, type B cats, you give them type B blood.
What about type AB cats? So type AB cats of course don't have naturally occurring alloe antibodies, so therefore, they, they could be a universal recipient, because of course they don't have antibodies against type A or type B. And that is the case if you were only using the red blood cells.
But of course, if you're giving up a unit of whole blood, there's a considerable amount of plasma with that. And type A cats will have some anti-B antibody type, antibodies in their, in their plasma. And type B cats will have actually relatively high levels of anti-A, antibodies in their, in their plasma.
So if you're using whole blood, actually it would be most ideal to use type AB blood because of course the plasmin doesn't contain any antibodies. But that's impractical because obviously type A AB cats are few and far between, it's very unlikely to get an AB donor. So therefore we tend to use type A cats as donors for type AB recipients.
And the reason for that is that type A cats will have relatively low levels of anti-B antibodies and therefore if there is a transfusion reaction, it should only be very, very minor. So, what is blood typing? So blood typing obviously relies on the presence of these A and B, red blood cell antigens on the cell surface, and is it the blood typing kits have impregnated antibody within them, so the, lines are highlighted if you like, when there is an antibody antigen reaction at the at the relevant lines.
So if you look at the, blood typing kit demonstrated on the screen here, you can see that this cat is a type A cat because there is a line at the type A marker. There is not a line at type B and therefore there is no antigen antibody reaction at type B, so this cat does not have any B antibodies, sorry, antigens on the red blood cell surface. And the C is the control line.
Just going on to a study which compared 5 different blood type and methods in cats. And the basically the outcome of this study was actually they looked at 4 490 different samples and they compared 5 different typing methods. And actually there was relatively good to almost excellent agreement between the typing methods.
But interestingly, what came out of this this study was that they identified 13 samples. Which didn't have, which had discordant results. Of these 13 samples, 4 of them came from FDLV positive cats, and in all of these samples, they were identified to be possibly type AB.
But actually using the tube assay, this identified the cats to be type A, and the tube assay is considered the gold standard assay. So all of the other assays also detected the type of antigen. However, some of the other assays also reacted to the anti-B antibody line on their, on their test strips and various degrees.
So that implied that they, the, the cats had both the A antigen and the B antigen. So this falsely identified the cats as type AB, whereas in fact they were actually type A cats. And the reason for this is not completely understood.
And it's thought to be that there might be some antigenic mimicry of the with the B antigens, so that's the FELV virus might be mimicking the B antigen on the surface of the red blood cells, perhaps. The other theory is perhaps there might be some interference in this CMAH enzyme activity, and that enzyme converts the type B antigen to the type A antigen in type AA. There's a possibility that the interaction of the virus with this enzyme decreases its activity and therefore, you get the presence of the type B antigen still on the on the red blood cell surface.
So the moral of the story after the study was that actually if you identify an anaemic cat that you find that is type AB, it's really important in this group of cats to test for FELV just in case. It's not to say that, you know, all FELV cats will have this abnormality, but it was just an interesting outcome of this study. So we've talked about the AB blood grouping system in cats, and that's obviously the most clinically relevant because there are naturally occurring antibodies against the A and the B, antigens.
But actually in real life, there's probably a whole heap of different antigens on the red blood cell surface, which are variably important and will, will cause variable antibody reactions in the recipient of this of this blood. So after one transfusion of an appropriately AB matched donor. You will get other new antibodies forming in the recipient against these kind of less important antigens that are on the cell surface.
And these antigens, these antibodies form in about 3 to 5 days after transfusion. Therefore, it is possible that if you then transfuse these, these cats that have received a transfusion already, if you give them another transfusion later on. It is possible that you'll get a a transfusion reaction because this recipient now has extra antibodies that it didn't have before.
So the way that we can predict these transfusion reactions is by performing compatibility testing or cross matching. So in simple terms, that is literally where you mix up some donor red blood cells with a recipient plasma, mix them together and see if there's a reaction. And as well, you can do the donor plasma with the recipient cells again, mix them together together and see whether there's a reaction.
Obviously cross matching is a little bit more complex than that, but, but essentially that's what you're doing. And that's basically a prediction of whether an animal will have a transfusion reaction when it receives a blood transfusion. Very occasionally though, there have been these transfusion reactions in cats that have never received a transfusion before.
But they have a transfusion reaction when they receive appropriately matched AB blood. So that must mean that the recipient cat must have naturally occurring antibodies because they haven't received a blood transfusion from previously. So you must have naturally carrying antibodies against another blood group.
So this study was published back in 2007, and this was performed off the back of, there was a, a, a cat that was identified, it was a renal transplant cat in the US, that had a hemolytic transfusion reaction, when it received, a unit of type A blood, it's a type A cat, it received a type A, unit, and it had a quite severe hemolytic transfusion reaction. So again, this raised the question that there must be naturally occurring antibodies against an unknown blood group. So off the back of this, the same group then identified 65 donor cats from their donor pool of cats.
And they performed blood compatibility within those 65 cats. And what they found was that there was actually another 3 donors that were cross-matched incompatible between the the donor plasma and other type A, cats, red blood cells. So this was major crossmatch incompatibility prior to, and this was, these were transfusion naive cats.
What was interesting though, these cats were all compatible with each other. So these 3 additional donor cats and the transplant recipient cat were all compatible with each other. So all of these cats must have had a naturally occurring antibody against a novel blood group.
And this new blood group is common to the vast majority of cats in the population, because obviously, the other 61 donor 62 donor cats were absolutely fine. And so those cats, the other 63 cats in the population, can't add up now, 62 cats in the population had the presence of this red blood cell antigen, whereas these incompatible donors did not have the antigen, but they did have a naturally occurring antibody and had a reaction. So this common red blood cell antigen has been termed NIC.
So this raises the question then, should we actually be cross matching prior to the first transfusion? Because we don't blood group from it, we only blood group for AB. So this study was, published in the UK a few years after the identification of the antibody, and they, found that they looked at 112 UK cats, of which 86 were type A.
They didn't detect any cross-match incompatibilities and therefore they, their conclusion was that there wasn't any significant AB, non-AB blood type incompatibilities and therefore there was not currently enough evidence to recommend cross matching prior to the first transfusion in the UK population of cats. But this was published much more recently in 2018, again out of the US, and they looked at, it was a retrospective study looking at 300 cats that received, red blood cell transfusions, and this was a whole, it was a very heterogeneous group of cats. Some of them, were transfusion naive, some of them had transfusions before, .
Some of them were cross-matched prior to transfusion, some of them were not. But what they found was that 15% of transfusion live cats had major cross-matching compatibilities. So maybe this 15% of cats were MIC negative cats, so had an antibody against the MC blood group.
And the conclusion of this study was actually that cross matches would be recommended prior to the first transfusion. So the honest answer is I don't know. But what we do at Davies is that we don't actually cross match prior to first transfusion, and that's because there is relatively limited evidence in the UK for these major cross matching compatibilities prior to first transfusion.
And actually cross matching is expensive, it's a faff, it takes time, and in the vast majority of cases, blood transfusions are needed as a rela relative emergency, so we don't tend to cross as much prior to first transfusion at Davis. So that was the challenging bit to get your head around and now on the slightly more practical aspect of the presentation. So where does the blood truck come from?
Where do we, you know, when we need to transfer a cat, where does it come from? Well, up to now. We've always had to use donor cats, so these, I'd like to introduce my little two fur babies.
Blackjack's at the front now, and, Hodge is there at the back. Hodge is more of a risk taker. He's sitting on the outside window ledge, more likely to need a blood transfusion.
And Blackjack is, sitting. Safely inside, both of my cats are retired feline donors. Blackjack was a much more successful donor than Podge, because Blackjack was, he was able to give blood conscious.
He never needed sedation, whereas Podge turned into, turned out to be a bit of a savage beast, and sadly was, he was, well, he was retired early, shall we say, because he, he, he, he wasn't the, the best friend of the vets that were trying to take his blood. So the Pet Blood Bank, on their website, they have lots of information about how you go about collecting blood from donors, and how to actually perform blood transfusions in cats. That's there's a link there to their, to their website.
There's a long feline blood collection guide, and they talk about exactly what you need, and they also talk about sort of appropriate, donors and so on. So there are some important points to take from that. Donor cats are, it's very important to be very selective about the donor cats if possible.
So donor cats are, it's ideal to use some heavier cats, greater than 5 kg, and needless to say, my two cats are significantly heavier than 5 kg. Podge certainly lives up to his name. So having a heavy cat's ideal, they need to obviously be healthy, ideally quite young, between 1 and 8 years old, so a mature cat, but, not an elderly cat.
They need to be regularly FDLV FIV tested. Regularly vaccinated, ideally indoors, but of course, that's not possible in all cases, as Pod was demonstrating, it was on the outdoor window ledge. I put sedation with a question mark.
It is ideal to select donors that, don't require sedation, and if they do require sedation, just a little bit, to, to take the edge off rather than kind of risking heavy sedation if possible. Having said that, it is also important actually to sedate a cat adequately rather than get them too stressed, because that can actually be detrimental, to their health as well. Ideally, it's important to maintain a closed collection system where possible and try and prevent air to be allowed into the collection chamber.
Ideally you need to be prepared, and it's the same with anything in life, isn't it? You need to be prepared, so calculate the volume that you need, make sure you have everything you need prior to start in the collection. Blood should only be kept at room temperature for 4 hours, if it's been, open to the air, and this is obviously relevant for when you're actually administering the blood product as well.
If more than 10 mL per kilo is collected from the patient, it's very important to replace that with an isotonic isotonic crystalloid, and we tend to recommend doubling the volume of blood collected, and give that replacement volume over about 60 to 120 minutes, so an hour or two. So just to introduce the case, so this was a little while ago, I saw Little Sweet Cheeks. Little Sweet Cheeks was a 4 year old domestic short haired cat when she was presented to me, and typically, she was presented to me at 9 o'clock on Friday evening.
Absolutely typical time for such emergencies to present. I'm sure we're all familiar with. On presentation, she was pretty weak and lethargic, and she was pale, she had very pale gums.
Her PCB was 8% and the CO2 protein was 50%. So she was significantly unwell, and actually I was quite surprised that she was even still vaguely ambulatory with a PCB of 8%. There was no clinical evidence of the coagulopathy.
She had normal platelets. So obviously, with a PCB of 8%, it's inappropriate to give her a blood transfusion. Bear in mind it's 9 o'clock on Friday night and any self-respecting cat is asleep at 9 o'clock on a Friday night.
Having said that, most cats are asleep 23 hours of the day, so, but it's very difficult to get a donor cat in at such times of night. The other problem on a Friday night is that occasionally you have owners that are unable to drive for various reasons. Don't judge me, this is my other little kitten, and this is Tyke.
He didn't really drink any of this beer, I promise. Also don't judge me on the type of bit. Anyway, back to little sweet cheeks.
So little sweet sheets for presentation obviously had very severe anaemia, and this was identified to be regenerative, and obviously regenerative anaemia, we always look, we always think it's hemolysis versus haemorrhage. I put chronic haemorrhage in brackets there, and, and the reason for that is actually little sweet treats was amazingly stable for a cat with a PCV of 8%. So I think his, his situation was a relatively chronic situation.
He was also norlimic, so there was no no . Evidence of hypovolemia in him, so there's no evidence of any severe bleeding. He did have a heart murmur exam.
And sort of again 9 o'clock on a Friday night. I didn't know whether this was a hemic murmur. That seemed very likely with PCP of 8%, it seems likely that he has a hemic murmur.
However, I couldn't rule out primary cardiac disease at this point and therefore, I also need to consider how much fluid can I give him, how much blood. Can I give him? And if I'm gonna give him blood, is it appropriate to give him whole blood or is there another option to give him, for example, just pack red blood cells, rather than giving him plasma as well, which would be ideal rather than, you know, risking fluid overload for giving too much volume.
So this brings me on to what might become available in the UK in the future to prevent us having the need to, you know, try and dig blood donors out in the middle of the night. So, of course we've all heard of the pet Blood Bank, and, the Petlo Bank are, developing a, feline blood banking, and, this is awaiting RCBS and BDS approval, and some proposals have gone through and as I say, they're just being approved. It's quite an advanced stage and we're hoping to get feline blood banking underway within the next 6 to 12 months.
And basically, much in the same way as canine donation, these, the situation will be that the cats, the donor cats are volunteered by the owners in much the same way as dogs are, and, it is now going to be that indoor and outdoor cats are accepted, but they are gonna be very, very thoroughly screened. The Pet Love Bank are very keen on on using conscious donors to avoid the need for sedation because obviously since sedation introduces a risk. And then, so prior to every donation, every cat will have a PCB in total protein.
They'll have FELV FIV testing and mycoplasma testing. They will also have a limited echo and a blood pressure check prior to transfusion. So prior to donation.
Every year they should have a haematology and biochemistry, and they will have their blood type performed on admission to the programme. And the the Peppa Bank have designed a bespoke closed closed collection system, which is absolutely unique. As far as I'm aware, there is nowhere nowhere else that has these closed collection systems available.
And this is really important to prevent contamination of the blood. So as I said before, one of the risks of using whole blood in cats, which of course we use when we have used blood donors, sorry, use feline donors of out of hours, donor cat in the hospital. Is that we have to use in most cats we tend to use whole blood, but actually component therapy is much more useful.
There are some indications for using whole blood, but actually component therapists say it's much more useful because it provides the most effective support. So if your patient has lost red blood cells, you can just replace red blood cells. If it's just got coagulation disorder, you can just give it plasma.
So you provide the most effective support for your patient's condition. And also it provides optimal use of every donation. So one cat can provide blood for two recipients because they can have one cat receiving red blood cells, the other cat receiving plasma.
In human medicine, there are a variety of different blood components available, but in feline, medicine, the idea is to predominantly have packed red blood cells and fresh frozen plasma available. And that fresh frozen plasma will become frozen plasma after 12 months, arbitrary 12 months, . And we'll go into that a little bit more detail in just a few moments.
So as I said before, it's very important when you when a patient requires a transfusion, that you try to replace what is missing, ideally no more and no less. And this prevents wastage and it's also safer. This avoids er volume overload or reduces the risk of volume overload.
And it also reduces the risk of any reactions and complications associated with the transfusion. So let's talk about packed red blood cells, and of course this is the most common component of blood that we use. So obviously, red blood cells are responsible for transporting oxygen around the body and delivering it to the relevant locations.
But what dose do we use? And this is a really difficult question to answer, and there's various calculations that we can look up online and the various publications and so on. But these calculations are a little bit flawed because they do, they don't really take into account the patient's underlying disease.
So obviously, if you have a patient that's, has, has a significant bleed in front of you, it's gonna require more blood than a than a cat that has a very stable PCP that does not have an acute acute blood loss that's continuing to bleed. So what I generally work on is that you need about 1 mL per kilo of packed red blood cells for every 1% desired increase in PCV as long as your patient does not have significant ongoing blood loss at the time of your transfusion. So let's go back to little sweet cheeks.
So when Little Sweet cheeks came in, she was 4 4 kg cat. Her PB as we know, was 8 8%. Her desired PCV, which was optimistic, I must say, was 25%.
So the increase in her PCV that's required was 17%. Quite a lot. So based on the calculation above, she needs 17 times 4, so that's 68 mLs of red blood cells.
And obviously, I've said it's unlikely to achieve this in a single unit of penine cells. In fact, it's absolutely impossible to do that. So, you're more likely to get about 25 to 30, 35 mLs in a unit of pack red blood cells in cats.
So her expected final PCV, using that calculation is probably gonna be about 15 or 16% in her case, if we use one unit of blood. If possible, we could give her 2 units of blood which is more likely to increase the PCP up to 25%, and actually that's not necessary because actually to . Take away the kind of life threatening urgency of the situation, a PCV of 15 to 16% is absolutely adequate, so it's not really necessary to give her two units of blood, even though it would give us a more ideal PCV.
So that brings on a little bit onto transfusion trigger. So when do we actually transfuse cats? And, we do get a lot of advice calls about this at Davis, you know, the PCB is this, should I transfuse you know, what PCB should I give a transfusion?
And actually, it's not really about the actual number. It is to a degree because obviously if your PCB is below 10%, I would, I would almost always transfuse a patient, because they are gonna, run into problems pretty quickly below below that sort of level. But above sort of 10%, it very much depends on the clinical status of the patient.
Of course we want a piece to be greater than 25 to 30%, but it's more about how stable your patient is. So, this is, this is back to tight, this was my beer drinking kitten, and if you look at the two pitch here, obviously on the left, he's a very bright, happy kitten on the right, he is potentially quite sick, unwell, you know, lying down, not looking so well. But this cat might have the same PCV, for example, this cat might have a PCV of 15%.
The cat on the left, I would not transfuse, you know, he's bright and happy, he doesn't seem clinically affected by his PCV of 15%. Whereas the cat on the left is obviously very lethargic and unwell, and he might be tachycardic or relatively bradycardia because cats do anything, and actually it's clinically indicated in his case to give him a transfusion even though his PCV is the same as the cat on the left. The other thing to consider when you're thinking about transfusion and whether you should give it is the patient's underlying disease.
So going back to little sweet cheeks, this is little sweet cheeks abdominal ultrasound scan. This is the stomach. We identified that, she had a mildly thickened gastric wall.
That was FNA, and actually came back as lymphoma. But of course these investigations were not done, late on a Friday night. They were performed the following day, and even then I didn't have the FNA results.
So in her case I couldn't really make any immediate decisions about it, whether it was appropriate to transduce her, but where possible. It's important to to try and perform some limited diagnostics to try and identify whether your patient has a very poor prognosis, because if you have a situation where you, for example, the dog has a huge liver mass and splenic mass and a hemoabdomen, . Excuse me, then it's perhaps inappropriate to transfuse that animal when in fact, they're gonna have to be euthanized because that's an inappropriate use of a very precious resource that we have available.
And I think that's even more relevant in cats perhaps compared to dogs. Yes, I am a cat lover, but I don't want to be using cats of blood inappropriately, as I say, it's a very precious resource that we have available. So I did feel a little bit guilty with little sweet cheeks.
Could, should I have transfused her? Well, I, I did feel very guilty, but actually the owners did want to go ahead with treatment, and she had an amazing response to treatment, and she lived for another year after her initial transfusion with appropriate, management. Unfortunately, after about 1 year, she did become anaemic again, and the owners selected to euthanasia at that point.
But she did do well, and I'm very pleased that I did, offer her that extra year of life by giving her a transfusion and follow-up treatment. Just one little aside, now obviously Little Sweet Cheeks was not hypoviemic on presentation, but this is just something I just wanted to highlight for you. .
It is very, very important to correct fluid status, and this takes priority over anaemia. And the reason for that is if you have a hypovolemic patient, the, the blood is not gonna be able to be delivered to, the relevant organs where it's required. And one common question that we see is, won't I dilute the blood?
Well, in a way, yes. So if you have a patient with a PCV of 20% and you give that dog a whole heap of fluids, that PCV will drop. But that doesn't mean your patient is becoming more anaemic as such, because ultimately, you still have the same number of red blood cells in the circulation, but all you're doing is improving the red blood cell delivery to where it's needed.
So I use this analogy of a red bus with people on it. So the red blood bus is the blood vessel, and the little people on the, on the red bus are the red blood cells. And what you actually need in order to deliver the people to their destination.
In the bus is some fuel, and that fuel is the fluid. So if you have a a bus that doesn't have any fuel, those people will not be able to be delivered to their relevant destination. And that's the same in blood.
If we do not have adequate volume, you will not be able to deliver those red blood cells. So, so volume status takes priority over your anaemia. You must correct that before correcting the anaemia, ideally at the same time, but don't delay giving fluids to your patient.
So what about plasma? So we talked about packed red blood cells, obviously one component that's gonna be hopefully made available with by the bank. What about plasma, the other component?
So main use of plasma is treatment of disorders of secondary hemostasis. So secondary hemostasis is the formation of your stable fibrin clot from your platelet club. And I've just put the sort of pathway that we all learned when we were at university on the slide here.
Essentially, that pathway does not truly rec reflect what happens in vivo, but it's a useful pathway because it allows interpretation of our diagnostic tests. So on the left there we have the intrinsic pathway. On the right there we have our extrinsic pathway, and they come together in the common pathway and that common pathway allows the activation of thrombin, and then thrombin leads to the activation of fibrin.
So with regard to feline coagulopathy, there are a few, so divide these, I've divided these into sort of inherited coagulopathy versus acquired coagulopathies, and of the, inherited coagulopathy, there's one that I think is particularly relevant, particularly important, and this is he deficiency. So this is a deficiency in factor 12, which is a very common deficiency in cats. This leads to prolongation of the APTT but a normal PT.
So if you look back to our last slide here, as you can see on the left hand side we've got the intrinsic pathway there. The intrinsic pathway, involves factors 12, 98, 1211, 9, and 8, sorry. So obviously with the deficiency of factor 12, you'll get a prolongation of the APTT.
OK, but your PT will be normal because your PT only reflects, factor 7 and tissue factor. But interestingly, and what's really relevant here is these cats do not bleed, and no treatment is required. So the relevance of this is that if you do coagulation testing in a cat that doesn't have significant evidence of bleeding and you get prolongation of the PTT, it might be that they have Hygen deficiency, Hagen deficiency, factor 12 deficiency.
And therefore they don't need any management for this, you can do whatever you need to do to the cat, without the risk of them bleeding. OK, so there's just, you just need to interpret your diagnostic test really carefully. Haemophilia, so that's, lack of factor 8 and, haemophilia B is lack of factor 9.
These are exceptionally rare in cats. I've never seen a case or never knowingly seen a case. I have seen cases in dogs, but they are reported, and it's worthwhile thinking of those.
You can also get inherited combined fat deficiencies, and you can get this vitamin K dependent carbooxidase deficiency in Devonre cats and the factors that this affects are your vitamin K dependent factors, so that's 279, and 10. So inherited coloss and cats are relatively uncommon. Apart from he deficiency.
But acquired coagulation, problems in cats are actually much more common, and the most common disease process that can lead to abnormalities in coagulation cats is liver disease, because all coagulation factors are produced in the liver. And the liver also, requires vitamin K for the activation of 279, and 10. So liver is very, very important in coagulation.
And the most common liver disease that can cause ama coagulation counts is hepatic idosis. Obviously, cats can fall into the, they can develop agenticide toxicity. And obviously, cats are much more sensible than dogs, and they are less likely to eat the, you know, pile of rat bait, but they do, of course, catch mice, so they can occasionally, have regenticide intoxication.
And therefore, and so rodenticides tend to affect your vitamin K and your vitamin K dependent factors are those 279, and 10 that we talked about before. And so one of your critical factors there is factor 7. If you remember back to that slide, looking at the, your APTT measures, the factors on, on the left-hand side of the diagram, on the right-hand side of the diagram, PT measures your factor 7.
Or reflect the presence of factor 7, and. In, redden so toxicity affecting vitamin K, obviously your factor 7 will be affected. You get PT prolongation first, and the reason for this is, factor 7 has a very short half-life in the circulation.
So if you get PT prolongation and a few hours later you end up with prolongation in your PTT. That is very suggestive of, rat poison. And then of course DIC can lead to abnormalities in your coagulation pathway.
So just talking a little bit more about liver disease, so quite often we want to perform liver biopsies in cats, and a lot of people suggest performing, you know, coagulation, parameters prior to collecting liver biopsies. But this study was published last year and they looked at the complications after percutaneous collection. Ultrasound guided liver biopsies in caps.
And what they found, they found a number of things and that of relevance to this presentation, they found that there was absolutely no correlation between the change in PCV, so bleeding, or other complications and the coagulation parameters. So it was almost pointless to performer pre-coagulation testing in this group of cats because it did not reflect their likelihood of bleeding. This did contradict a previous study though, where they, they identified the cats that had that had a significant prolongation in their PTT were more likely to bleed post liver biopsy in, in cats.
So this is the conclusion of this is I don't really know whether to recommend coagulation parameters prior to to collecting liver biopsy. But what I would say that if you get normal coagulation parameters prior to liver biopsy, do not be fooled, these CAT scans still bleed. So, just bring us on to them, so what sort of plasma might be available?
So the first is fresh whole blood, because of course whole blood does contain plasma, but the, coagulation factors are only active, for the 1st, 6 hours, but all of the coagulation facts that are active only for 6 hours in, so it's important to use fresh whole blood if you want active coagulation factors. However, using threshold blood is only desirable if your patient is also anaemic, because obviously if you don't have an anaemic patient, the red blood cells are not required. So if you have a patient that's not actually anaemic and you just want to replace coagulation factors, it's most appropriate to use plasma.
So as I alluded to briefly before, the PET blood bank is gonna have fresh frozen plasma available. So this is plasma that has been frozen within 8 hours of collection, and is, it remains as fresh frozen plasma for 1 year, and after 1 year it arbitrarily becomes frozen plasma. And within fresh frozen plasma, you have all the coagulation factors, so it's appropriate for use in any of your coagulation disorders affecting secondary stasis.
Frozen plasma is plasma that's been frozen within, between 8 and 24 hours and then used within 5 years. And within frozen plasma, your factors 8 on Willebrand factor and factor 5 become inactive. So, it doesn't contain all your factors, but it does contain factors 279, and 10, which are your vitamin K factors.
So it is appropriate to use frozen plasma in patients that have had progenticide poisoning. So a lot of people suggest, well is it then useful to use plasma in hyperproteinmic patients? And this is not true.
It is not appropriate to use plasma to replace protein. About 45 mL per kg is needed to increase your albumin by 1, and obviously this is a lot of plasma, to increase your albumin by a relatively small amount. So I would not recommend use of plasma for treatment of hyperthyroinemia.
So, obviously up to now, and we have found it very difficult to get hold of feline blood, particularly in an out of hours situation, and there is this, pet blood bank are working very hard to develop a new programme of feline blood banking. But obviously there might be situations in which we are absolutely desperate for blood and we don't know what to do because we don't have anything available. At the moment.
So this brings me on to xenotransfusion, and xenotransfusion is the use of, blood from different species, in, in this case cats. So there's several publications about this, now. The one I wanted to draw your attention to here is the one at the bottom of the screen, published in 2017, and this was a lab-based study that looked at cross matching essentially in cats.
And what they found was that there was a a very high level of in vitro incompatibility with greater than 80% of their cross matchers finding major incompatibility. And this is between, cats against dog erythrocyte antigens. So having major cross matching compatibility when cats have not previously been exposed to drug erythrocytes, this means that there must be naturally occurring antibodies in cats against canine canine erythrocytes.
This study was published very recently, just in the last few weeks. It's a prospective study published in JSAP and it was really interesting. It looked at 49 xenot transfusions that had been performed, and of these, xenot transfusions, 29 of them did actually have cross matches, of which there were 20 of them actually had major incompatibility, but they were still used, .
And 2/3 of the recipients did unfortunately have hemolytic transfusion reactions, and they developed electromolysis about 2 or 3 days later, 2 or 3 days after the transfusion. But they didn't have any severe side effects, and none of these cats were reported to have died as a consequence of their xenot transfusion. That's the receipt of canine red blood cells.
But obviously, if they were having transfusion reactions, hemolytic transfusion reactions within 2 or 3 days, the canine red blood cells were probably all healized 2 or 3 days after the transfusion, but that 2 or 3 days might be enough. To start your cat on relevant treatment for its underlying disease process, for example, if it was a surgical complication, it was bleeding, it needed blood then hopefully within that 1st 2 or 3 days, the underlying cause of its bleed or whatever could have been sorted out and actually, in those cases, the Xenot transfusion could have been life life saving. I still wouldn't necessarily advocate it and I would still only do xenotransfusion absolute last resort, but it is something that is potentially possible, as I say, I cannot emphasise enough, it is an absolute last resort.
So just a few practical tips and risks as well just to finish with. So when administering blood or plasma, it's very important to, use a, appropriate blood giving set, and they contain a philtre. If you don't have blood giving sets available containing these philtres, then you can get these inline philtres which featured on the top right, of the page there.
And the idea of filtering is just to remove any clots and debris that might be present within your, donor unit. And then there's a question about using fluid pumps. Now fluid pumps are really appropriate to use, they prevent fluid overload, they, you know, just rushing into our patients and so on.
Also enables us to monitor very, very carefully how much blood the patients have received. You can set alarms and so you can monitor your patient very carefully throughout your the transfusion. So fluid pumps are useful, but a lot of fluid pumps can actually lead to hemolysis in your of your unit, so it's very important to, .
Try and find out whether your, the fluid pumps that you use in your practises are actually compatible with blood transfusions because there are some pumps, so we use the the the bran pumps and it's fine to use those for blood transfusions, but there are other pumps that are not appropriate for use for blood transfusions. So it's worth just finding that out in your practises. One thing that I forgot to mention a couple of slides ago actually with administration of of plasma specifically is that actually, obviously we know that it's very important to blood group cats prior to administering of packed red blood cells.
However, it is also very important to blood group cats prior to plasma transfusion, and the reason for this is that cats have naturally occurring alloe antibodies which are present in their plasma. And so obviously in a donor plasma, if they haven't received any blood before, they're still gonna have antibodies. So if you give the if you do not.
Blood group, your recipient, you might give them an inappropriate unit of plasma from a different blood group of cats, which can lead to probably not major transfusion reactions, but there might be a a minor transfusion reaction there. So it's very important to people with plasma which is different from in dogs where we wouldn't, we wouldn't need to give appropriate blood group because they do not contain naturally occurring antibodies. So again, administration here, so, very important to go very slowly, particularly at the very start of the transfusion.
So for the first sort of 15 to 30 minutes, go really slowly administering the blood or the plasma between 0.5 to 1 mL per hour. If that's tolerated, the rate can be increased to 4 to 6 mil per kg per hour.
Very important to give your blood over a maximum of 4 hours. As I said before, the risk of contamination in your blood units, increases significantly after 4 hours. And try to maintain a closed system.
So if your patient needs to go out for a week during its transfusion, then try not to detach your unit because this will lead to a higher risk of contamination, equally if your patient needs some diagnostics done and so on, try not to detach your blood. It must, you must maintain a closed system where possible. And obviously monitor the TPR of the patient, the patient's demeanour if there's any nausea, any itching of the skin, any swelling and so on.
As you can see here on the right, that's my patient little Winnie, and she had a, a transfusion reaction there, and it's pretty obvious, swelling of her skin. So transfusion reactions come in all shapes and sizes. They're divided into two groups broadly speaking, and sometimes it's actually very difficult to differentiate kind of what type of transfusion reaction your patient is having.
But they, broadly speaking, they're divided into immunological and non-immunological reactions, and your immunological can be hemolytic, non-hemolytic, and then any of your reactions can be acute at the time of transfusion or delayed a little bit later on. So I guess the most severe and I guess obvious transfusion reactions that we see are those acute hemolytic reactions, and this is where patients develop in intravascular hemolysis, and this tends to be where you have true antigen antibody reaction essentially often because incompatible blood has been administered. And the clinical signs of this are fever, tachycardia, dyspnea, muscle tremors, and so on, and you can all read the slide.
But specifically on that, I haven't written, written jaundice, but jaundice can be a feature. But hemoglobinuria, is also a feature. Obviously, patients with IMHA might already have hemoglobinuria, but if that's a new finding during your transfusion or immediately after transfusion, it's very indicative of a hemolytic transfusion reaction.
These transfusion reactions can be very severe. Your patients can be in shock. DIC can have acute kidney injuries and so on.
Now, it's very important, it's pretty obvious you stop the transfusion if you see anything like that, and do not restart that transfusion with that same unit, and then administer treatment as required in this case it should be fluids. Non-hemolytic reactions are relatively common, and they're essentially similar of allergic anaphylactic type responses. With these, reactions, it's obviously very important to stop your transfusion.
You can administer chlorphenamine, for example, plus or minus steroids. If your, clinical signs improve very, very quickly, you can potentially restart those transfusions very, very slowly, and monitor your patient, but if you get a second reaction, then you need to give up, and consider trying a different unit. If there's any sort of signs of anaphylaxis, your patient becomes hypertensive and so on, obviously you need to treat that appropriately and not restart the transfusion.
And then, delayed imm immunological reactions, essentially this is where you get hemolysis again, but 2 to 21 days post your transfusion. Usually these are less severe and intervention is very rarely required. And then non-immuno immunological reactions can also occur and they tend to be associated with the anaphylactic responses to associated with to rapid administration.
And that usually subsides when you slow down, stop the transfusion. But other non-immunological transfusion reactions can include overload, which we mentioned briefly, and with regard to whole blood transfusions in cancers, hypercalcemia, polycythene, if you give too much blood, dilution of coagulopathy, thrombosis, contamination, which is not uncommon, and air ambulance, much like, if you're giving normal fluids to patients. So in summary, Cats have three main blood groups, your A, B, and AB.
They also, some cats, well, the majority of cats in the population seem to have this other blood group called Mick, to which MIC negative cats have a naturally occurring antibodies. It's very important to cross-match cats if they have received a transfusion more to, more than 3 to 5 days prior, and this is a this is a consequence of the formation of new antibodies, when they refu when they receive a transfusion. But in cats, maybe it's worth giving them or having a cross match prior to their first transfusion.
Of course this is debatable and that's not something that we do at Davies, but it is something that could be justified. We've then talked a little bit about the future of feline blood banking, and it's very, very exciting to report that hopefully within the next 6 to 12 months, Pet Blood Bank are gonna start feline blood banking. And then we talked a little bit about when to use which products, so packed red bloods, packed red cells versus plasma, and, when it's appropriate to transfuse, and that's, it's based on patient factors primarily rather than a specific PCB.
And how much blood to give again is, based on, you know, these calculations, yes, but ultimately it depends on how your patient responds to the transfusion, and once they are clinically stable, then it is OK to stop. We talked about a enot transfusion, as I say, this is for emergency use only and it's not generally advised. When you actually administer blood products, it's very important to use a philtre, go slowly, administer no more than 4 hours, and using fluid pumps is controversial.
You just need to check what fluid pumps you have and whether it's suitable. And then obviously transfusion does carry a degree of risk and complication. You need to monitor patients very, very carefully, and identify whether it's appropriate to, whether you need to actually stop your transfusion completely or whether it's appropriate to restart them if you see a transfusion reaction.
So just a little plug, obviously we've talked about predominantly feline blood donations here, but it's very, very important for us to give blood as well. Is, you know, the, the NHS is, is desperate for blood stocks. So if, if you're healthy and young, then I would strongly recommend that you give blood if possible.
So, after that I would welcome any questions, and if you're listening after the live presentation, then obviously just email me with any questions you might have. And that's my current, working from home companion at the moment. He supervises absolutely everything that I do.
That's rather old than he did in the earlier photos. You know, thank you for listening.
