Hello everyone, so today we are going to, talk about transfusions. So I, my name is Alice. I am one of the, vets at DWR Veterinary Specialists.

I am an emergency and critical care specialist there. And really what I wanted to chat to you, about is everything about transfusions, dog, cats, and try and cover quite a few questions that you might have about, needing to transfuse a patient in your practise. So what we are aiming to cover today is how to recognise transfusion triggers.

So I feel like that's a common question really about when do I need to transfuse a patient? Is this patient in need of a transfusion now? So kind of like trying to figure this out.

And also choosing the appropriate products cos we've got quite a few at our disposal and it's not always easy to know which one is the best product for the patient, so we'll try and cover that as well. Understanding blood compatibilities, as we know, not everything goes with everything. We need to make sure that we've got the right blood product for the right patient and that we are going to avoid transfusion reactions.

And that's why we are going to cover as well how to monitor a transfusion, what we're monitoring for, and obviously the whole reason why we are monitoring a transfusion is to manage, to recognise and then manage transfusion reactions if they were to happen. So hopefully you'll be familiar with all these things by the end of this lecture. So when and who to transfuse, I always feel like it's a bit easier to follow something if there's a real life case, associated with the lecture.

So, all along this lecture, we're going to try and follow Henry, who is a little cat I saw during my residency and got quite attached to, and. So I, I thought I'd I'd take him, I take you guys through his story. And he's a 4 year old man to domestic short hair.

He went out and like was found by members of the public, not very far from his house, but clearly not in the perfect state that he was in before he went out. And and so he was brought in by his owners who, suspected that maybe had an RTA because there was a road not too far from their house. As you can see on his radiographs, he had broken his tail and also broken his pelvis.

And so that was what had been seen at the referring vet. He had a tail pole injury associated with that. And when he came in, he had been primarily stabilised at the at the referring vets, had had some pain relief, and, and he was referred to us for further management.

So the day prior to referral, he had been on 4 mLs per kilo per hour of crystalloids, so that was for a total of 28 hours. And when he presented to us, he had an increased respirate and effort, and on auscultation there were clearly some crackles that were auscultated. So first thing that we did when he arrived to us was to stop the fluids because clearly he had not coped with that so far and gave him a bit of furosemide to see if he could kind of get rid of this fluid that had gone over and overloaded him.

As you can see on the radiographs, there was some pulmonary edoema associated there, with this fluid overload. So, it's kind of like a common pattern to see when, when you have fluid overload, seeing, seeing this edoema that collects in perihilar region. On his focus, we just did an LAAO.

We kind of like love, LAO ratios in emergency and critical care to see if, if there's any evidence of fluid overload, seeing if that left atrium is a bit too big. And indeed you can see here it should be 1 to 1.5.

The diameter of the aorta and here in the left atrium, you can see probably we're around 2 eyeballing it. We love to eyeball it in in the ECC world as well. We're not doing precise measurements like our cardiologists do, but I feel like roughly here we can see that there's an enlargement of the left atrium, which is also one of the things that we tend to see with fluid with fluid overload.

And the famous bee lines on pocus, which I'm sure you, you recognise as well. So you just put the probe on the chest and, in case you end up having some what we call wet lungs, you can see those, those bee lines there. So in the case of a trauma, be careful because it could be that this is bleeding actually that's happening in the lungs and beelines won't be able to differentiate.

That from pulmonary edoema and from the fact that in here we're more thinking that he's been fluid overloaded and or it could be a combination of both in this case because we know it's a trauma, but just keep in mind that obviously there is that there is a component of wet lungs, but this could be a bit of haemorrhage in the lungs or this could be fluid overload. In our case, we've got quite a lot of evidence now that this little cat has been fluid overloaded. In terms of transfusion requirements, because you're probably thinking, why is she talking about this if we're talking about transfusions?

And, when he presented to us, on admission, his PCV was 42%. And yet two days later on the Saturday, his PCV was 18%, so a fair drop. And I feel like, I often get the question, it's like, well, his PCV was 42%, now it's 18.

Do I need to transfuse my patient? And unfortunately the answer is it depends on what your patient is, what's going on with him. It's kind of an individual answer and there is no golden number where I will say yes, you need to transfuse.

I mean maybe if you tell me my patient has PCV of 2, yes, very likely you, you need to transfuse and I probably don't need to know much more about this patient. But in almost every other situation, my answer will always be it depends on how the patient is and what the situation is. So, when it comes to Henry, his heart rate was 200 at the time on, on the Saturday where his PCV was 18, with the respiratory 32, he had good pulses, his CRC was 1.5 seconds.

We had blood typed him, and he was blood type A. And his surgery was planned on Monday. Now when we look at the literature about cats and, pelvic fractures, well, pelvic injuries in general, there is a nice paper out there and, it tells us that about, 18.8%, well, 18.8% of of cats in this study, required a blood transfusion when when they presented with a pelvic injury.

So we kind of keep that at the back of our mind thinking, well, he's a cat who has had a big drop in PCV. For the moment, looking at his vitals, I'm not convinced. That he has all the triggers that I want to say he's unstable enough to require a blood transfusion right now.

But I know that he's in a category where patients like him have needed transfusion. Like 1 in 5 patients presenting like him will need a blood transfusion. So there's already kind of like a bit of a bias in my head.

So what I need to consider right now is that he is currently cardiovascularly stable. His heart rate, as we say, is 200, respirate 32, he's got good pulses, his CRT's fine. I know that he's been recently fluid overloaded.

So right now, his LAO focus is 1.8. He's got some bee lines.

So ultimately my transfusion is also a fluid therapy. It's, it's obviously blood products. It's a transfusion, but it's more fluid that I'm going to put in this gap who's already been overloaded.

So that will definitely also play a role in my head in terms of deciding when and whether or not I transfuse him. His PCV has dropped quite a lot. As we know, it's now 18%.

It's down from 42%. And on Monday, which is in 48 hours, he's having surgery. So I know that there'll be an event where he will lose more blood.

So again, that's also in my head thinking, well, I can't really let this gap go on and on with the PCV. Let's say I'm really lucky and he doesn't drop his PCV any further. He stays at 18%.

Well, on Monday, he's definitely going to have something that will mean he will lose more, so that also needs to play a role in my decision. So in terms of timing, so that we know where we're at for Henry, on Saturday he came in, he was fluid overloaded, so we were very cautious, didn't give him any fluid, any more fluid, and we were. Thinking mainly we need to have some nutrition in him to prepare him for Monday for the surgery.

And that is how the intake could be to to maintain him. So in this case, if he's not eating on his own, placing a little feeding tube to to help with that. .

But then on Monday, I know that I've got the surgery that really what I would like for the surgery is his PCV to be 25 or above for the moment we induce him. And so really I need to go and do some retro planning and then say, well, in this case, I will transfuse him on Sunday night so that I am in a good position on Monday for induction. And I know that I can.

That transfusion 12 hours before the induction of GA so that I am in a good place for for for the induction and and for the surgery if he has any blood loss during that, which he will have some, he could have more than I want, but he will have some blood loss there. So in terms of like whether I transfuse Henry, then that's a yes for me because of all the reasons that we've just covered. And in terms of timing.

Then let's try and get as much time as possible whilst he's still stable, to kind of like get rid of some of the fluid since he's been overloaded and I'm eventually going to give him more fluid with the blood transfusion. But also knowing that I, I can have that in mind, thinking I need to get him in a good place to receive this blood transfusion and then to have his surgery on Monday. So the answer is yes, I will transfuse Henry, and when is, well, really when it works, hopefully for me and for him, which is Sunday night.

And on Sunday evening, his PCV was 15%. On physical examination, his heart rate was 220. His res rate was still 32, but his pulses had become a bit hyperdynamic.

His mucus membranes were pale pink. His CRT was 2 seconds. We had improved on the side of things of, focus and fluid overload.

He, he just had like 1+ be lines in perihila bilaterally, which is obviously an improvement from what we had before. And his LAO had also decreased and it was more 1.5 now, which is acceptable.

And I knew that I wanted GA in 12 hours, and, and then surgery, and so I was aiming for a PCV of 30% at the time. And so that's when I'm thinking now, OK, let's talk about what I'm going to give him and, and how long over I'm, I'm going to give that transfusion. Obviously the first question here is what blood product am I giving him?

Might be a bit of an easy answer when when we're talking about Henry because obviously we're we're talking about some haemorrhage. He's got pelvic fractures. He's bleeding from there.

He's had a trauma. He's probably got other bleeds, as you can see on his abdomen. There's there's large hematoma there.

So it's going to be an easy answer for for Henry, but you might have some different scenarios, in, in your practise and, and you will wonder what to give them. So we're just going to cover which blood products are out there. We're obviously not gonna cover every blood product that is, is out there or or not available everywhere anyway.

But the main ones I'm hoping to be able to answer quite a few of your of your question. So when you grab blood just from a donor, what you get is whole blood. From the whole blood you can make packed red blood cells, which is obviously a concentrated version with of blood with more red blood cells in there.

And then plasma is what you will get as the super agent of that, and there's different types of plasma. There's fresh frozen plasma, there's stored or what people just call frozen plasma. Cryoprecipitate, cryoproplasma, or cryosupinate, and these are all different forms of plasma or things that you can get from plasma.

And then again, platelet rich plasma is also something that you can get from plasma, and that will have a higher concentration of platelets. All of this, all together, so your packed cells, your plasma and your platelet rich plasma like can all all be part of, of a whole blood unit, but obviously not all, not all of our patients who are coming in, in need a a whole mix of everything. And in our case.

For now, it's, it's quite common that actually trauma patients will need a bit of everything, but in our precise case now for Henry, we don't particularly think he's got coagulopathy. We just think he's bleeding from from the trauma that happened on on the Thursday. So what I'm after here is probably packed red blood cells.

I've always like kind of wondered before, how those blood products, for those of you who are using the banks, you kind of like get those units already and, and it's easy to not really wonder how, how they get made. And so I think it's quite interesting. And that's a video that I made with the obviously blood transfusion team and they have like a wonderful team who works there.

And so I kind of like went to have a look with them to see see how it's going. And so what they do is from the donor, then it's then connected to a multiple pack closed system collection bags, and that already contains the, the citrate in there, and you can see that it's kind of with the system of suction being sucked into the bag whilst the patient is not sedated, just, just very good donors, there, and they get in that way between 450 and 500 mLs of whole blood into a single collection unit. And, and then we'll see what happens to that unit.

But if you were to give whole blood, then that would be the end of the story. It's, it's there and it's it's you could use that bag straight away. But then, so the whole blood, the bag that you get that you see there will get centrifuged if you don't want to use it like that, which is like the most common blood products that we probably use.

And, and so that big centrifuge will help, basically put the sedimented red blood cells at the bottom, and, and then you'll get a buffy coat, which will then help make the plasma. So you can see here, what the bag looks like after it's come out of the centrifuge. So at the bottom there you see the red blood cells.

Then, just on top of that you've got a small buffy coat, and then you've got the snatent plasma, which is usually between 150 and 350 mL. And that will be kind of pressed from the bottom to to express the plasma, which is the snatant. To then go in a separate bag which will contain plasma, so you need to like press it enough that all the plasma goes in and avoid having too much, too many red blood cells that are going in there, and and so you end up on one end with a pack cell unit and a unit of plasma.

In terms of different types of blood products and plasma and things that you can do to these products that I've shown you now, to make them different things, this is A very busy diagram for to understand which ones are which and and what happens to them, but globally, the ones that we should discuss and know about are potentially the ones that you you might use more, are if you grab fresh whole blood as we've just seen, you end up with a bag of packed red cells and a bag of fresh plasma, and if you, If we were using different types of centrifuge force to make platelet rich plasma, we could have basically a layer that contains more of the platelets from the fresh whole blood, and so that will end up being a small volume of plasma that will contain most of the platelets of the bag of whole blood that's just been drawn, and that is just by playing of the settings of the centrifuge. And so this platelet rich plasma can be used for thrombocytopenic patients. So they will act a bit as a as a bandage really, like sometimes pack cells when when we need to use them in in some cases, but they they won't last very long in the patient.

But if you have a patient with an acute bleed who's thrombocytopenic, then those those platelets. Donor can can help. And so, and it's a relatively small volume.

It can be anywhere between like 50 and 70 mLs of of platelet rich plasma, which will give the equivalent of of platelets that was in in the threshold blood unit. And the packed red cells are the ones we're familiar with. Usually the PCV of the packed cells.

Is about 65% because obviously you've gotten rid of of plasma and so you have an effectively concentrated blood blood volume. And then the fresh plasma is there, which if it is basically frozen straight away, processed and and frozen straight away, is fresh frozen plasma which keeps most of the coagulation factors that we might be interested in. But that is only true for a year in the freezer, so if it stays more than a year in the freezer, it's no longer fresh frozen plasma because we drop some of those coagulation factors that we might want to use.

And again if you process that, fresh frozen plasma into, cryoprecipitate and cryosupinant, so, that will, the cryoprecipitate will be as it indicates it, when, when we kind of like defrost fresh frozen plasma, it, it makes some little kind of ice bits that like are going to to make the cry precipitate, . And these contain a lot of some factors, for example, factor 8, which will be helpful in the case of haemophilia A, for example, where, where they are missing this factor 8. And, whereas the cryosupinant will, as a result, have more of other factors that haven't gone in the cryoprecipitate.

So again, this is all made from the same bag. So the, the things that you mainly get in the cryoprecipitate won't be in the cryosupernatant and vice versa. But for example, cryosupinant will have, all the factors that we need in a vitamin K, deficient dog.

So any rodenticcyte toxicity or anything like that, then all your 279, 10 will be in your, in your cryosupinant. So that's a, that's a good one to remember if you are facing these cases. The peddler bank has a very helpful diagram for decision making in, in cases of plasma transfusions.

So for those of you who do end up using plasma and are wondering which ones can I, can I use, so, you can, for example, we were talking just right now about cryosupinant, you can, you can follow like does the dog have a coagulopathy. Yes. And then is it vitamin K dependent coagroup C, for example, if you know that there's that the dog that you have has eaten some rodenticide, you can see here that it will help you tell, say you can use fresh frozen plasma or frozen plasma because again it will have a bit of everything.

It's not being processed any further, but if you want to be even more specific, then it tells you you can use cryosupinate and. So if you do store quite a few different products and, and you like having the choice and and using the most appropriate products, this can be really helpful in your decision making for, for plasma. In our case, I thought I would, I would put that here to, to be helpful.

And, and I was telling you as well about any factor 8 deficiency. So if you have like a haemophilia A. Again, if you follow that tree, does the patient have a coagulopathy?

Yes. And then if it's not vitamin K, is it von Willebrands or factor 8 or fibrinogen deficiency? And then if it is that case, they say it needs cryoprecipitate because as I was telling you, factor 8 will be concentrating in that cryoprecipitate when the plasma is gently thawed.

And it goes for the the same for von Berbrand's factors and fibrinogen. So anything that you need for that, like if you have a patient who's got haemophilia A presented to you, then cryoprecipitate would would be the way to go. Then we're still talking about Henry.

We've decided from what's going on with him, what we need, at this moment that we need, packed red blood cells, . We could also, let's say we had a feline donor coming in, we could also say, well actually your whole blood will be quite good. The reason why I would probably, towards the size of packed red blood cells over whole blood is because Henry has been fluid overloaded.

So if I can have a smaller volume to transfuse him rather than having more, which is would be the case if I had whole blood because I would obviously have also the plasma of of the donor in the air. For a patient who at the minute does not need plasma particularly, then that is what would make me go more towards black red blood cells. But equally if you're in practise and, and you have no access to, feline pack red blood cells, and, and you have a donor coming in and you can only use whole blood, then that's OK as well in this case because you, you need the red blood cells really being transfused to Henry.

But you, for cats, you, you do need to blood type. I think all of us are, are quite familiar with that. They, they need, we need to know if they're, that they have been AB type matched, because they will need to get type match products for, for their blood type.

So the way it works, and the Alvida website is, is quite helpful if you have a doubt. It's, it's an easy one to consult and, and have a look at. So if your recipient is type A, it needs to get, type A red blood cells.

If it's type B you need to get type B red blood cells, and if the cat is AB, obviously the best would be to get some AB red blood cells, but if it's not possible, then type A, red blood cells are acceptable as well. And then the reason why we worry about that is if, a type B cat receives some type A red blood cells, there will be a very big, likely hemolytic reaction that will happen, which is obviously not what we're after. And the PCB won't go up and and would potentially be sicker.

And we could say, well, do we really care like how many type B patients do we actually see? But there is a study from 2007 looking at how many type B cats we see in the UK. And, and we could say like, well, basically, do I just blood type all the posh cats?

And, and, and don't bother with the ones that aren't pedigree cats, but actually there is a fair proportion of type B cats, in the non-pedigree cats as well. So for example, for this study, you can see that the pedigree cats, 13.7% of them were type B with 3.9% were AB and 30% of the non-pedigree ones, and 2% 30% were B and 2% were AB.

So I think realistically, we we need to blood type because in in the UK, well this is obviously one hospital in in southeast of England, but, but there is a fair bit of BAs presenting to us and say we cannot go blind on on these cats and and they need to be a bee type match to to know which products they they are getting. What about dogs, because obviously we're talking a lot about Henry, but, but we also want to know about what to do with our dogs. So dogs have at least 5 blood types that we're aware of.

DEA, this stands for dog erythrogen antigen, erythrocytes antigen, sorry. And so, . The main one that we test for, as you probably know, is the DA one, because it's the most immunogenic one, but each dog will be positive or negative, i.e., possess or not the corresponding antigen on the red blood cell surface for 1345, and 7.

So one dog that presents. You could be DAA1 positive, DA3 negative, DA4 positive, DA5 negative, and DA7 positive. But the main one we're going to worry about is DA1, because it will be the one that will be the most immunogenic and is the most likely one to then cause reactions if it's not matched to to that antigen.

And the one thing with dogs is as far as we know there are no natural aloe antibodies to red blood cells of a different group, so the dogs will not already have, antigens against red against, sorry, antigens that they do not have on, on their own red blood cells. So that's why. You've probably heard that before.

For the first transfusion, we say that they can receive blood from a different group to theirs. And in an emergency situation, it is acceptable to not blood type and give as long as we're sure that it is a first transfusion to give any blood type. Give a dog who is potentially DEA DEA negative, DA1 negative, a DEA 1 positive unit.

But that's only true for the first transfusion because then it will induce the production of specific antibodies to those red blood cells that have been transfused, and they will likely be a reaction to another transfusion with a with blood of a of a different group. Again, the LBD website is is very helpful if you have a doubt. But if, if you have a donor who's DA1 negative.

He can donate to both a positive and negative patient because he won't have that immunogenic erythrocyte, antigen, whereas a DA1 positive dog can only give to a positive recipient. Again, that is very true for any subsequent transfusion. For the first one in an emergency setting, it is acceptable not to know.

There's this like very nice website. It's not a promise, it's not because it's a French website that I've picked it, but it is, it is a very nice one. Where they explain mainly to owners to kind of like see if if they would want their dogs to to be enrolled in in a donation programme if they're appropriate donors and how that works.

And so, it kind of like summarises what I've I've tried to explain here that for a first transfusion, both the donor and recipients like have no antibodies and so, a DEA one positive dog can give to a DEA one negative dog. And however, during the second transfusion, there will be antibodies which will have been created against the cells that have been initially donated if if the dog was a negative dog and received a positive unit, a positive unit, and there is when we think there will be a transfusion reaction. So for Any subsequent donation, sorry, transfusion, make sure that you have blood type your dogs, and, and, and that you, you know what you're giving them.

And if, if the story is unknown as well, if, if you're not sure and and it's possible that this dog's been transfused before, then it's always better to be safe and and type them. So when it comes to plasma, I think that's another like quite common question because we get confused with which one is what, like blood plasma, like do I need to blood type for all of them. So for dogs, no, you can give a dog, like you can give positive plasma to a negative dog as many times as needed.

It does not matter because effectively you won't have the antigen in, in the plasma if it's positive. So, yeah. It's it's totally fine to, to use plasma of of any kind to to transfuse your dogs.

So if you have a patient that's coming in and you don't have the time to transfuse them, to sorry, to blood type them before transfusion, but all you're gonna give them is plasma, it's fine not to blood type them. And, and, and you can, you can give any unit of plasma to, to any dog. It's not true for cats, and you do need to blood type to to give plasma to to cats.

So, again, if you have, a cat who coming coming in who is, obviously type A, you need to give type A plasma. If it's B, you need to give type B plasma, and if the cat is AB, you need to ideally give type AB plasma. But if again you don't have AB.

Which is quite rare because as you saw before, at least in England, it's not a very common blood group, blood type. Then you can use, type A plasma for an AB cat, but it is always better to get to get AB, but you are less likely to have reactions if you if you use type A. How to blood type, it's probably a procedure that you guys are are quite familiar with and it that it is is not hard to do in practise.

The ISFM consensus guidelines explains it quite well, and this paper is open access, so if you ever need to refer to it, then please do. And they take you through different methods for blood typing. And there's those little cards that some of you may be familiar with if that's what you're using in practise, where you mix some of the EDTA blood from the patient to blood type with the reagents that you then put on, on the three bits of the card.

And the reason why you get the first bit with the auto agglutination saline cyanine screen is because the type will be the one where you will see agglutination. So in the one that they're showing you there, the cat is. Type A because you can see that there's some agglutination happening in the type A case.

But if the patient has IMHA, for example, and is auto agglutinating, then you might get an error effectively because they were all agglutinate and you might think that the patient's A, B, or B, if for any reason it's not agglutinating in the right place. And so that's why you also have that auto agglutination, slide there to check and if it is auto agglutinating, then you can't rely on the results that you will get there. And the Arvidia kits as well are are there for a point of care, a blood type on patients.

They exist for dogs and for cats. Again, you put a bit of reagent with, with some of the blood of the patient, and then you dip the, little plastic device with a membrane dipstick in there. And you wait for it to migrate.

The C is the control line, so wherever you'll see a line on top of the C is whether or not your patient is positive for that antigen. So for cats, if you see a line at A, B, and C, the patient is A, B. If you see a line at B and C, patient's B.

If you see a line at A and C, patient is A. Please make sure that you always have that control line there and that it is, it is, it validates the, the test. And same for for any dog that you blood type using those kits, if you get a line, even a faint line at the DEA1 mark, then the patient is positive.

It's only if you get either a white line or nothing going on that the patient is negative, and again the control line should always be there and you should always have a line at that point. And then the other question that often comes up is then do I need to cross match my patient before every transfusion? And the first question you might have is what's cross match?

Like I hear a lot about it, but, but what is it? There's two types of cross match, there's the major cross match and the minor cross match. The major cross match is the one we mainly worry about because we want to know if the donor red blood cells that we're going to transfuse into the patient are effectively going to be attacked by the recipient's serum and antibodies in there.

So we mix a bit of the donor red blood cells with a bit of the recipient's plasma. Or serum. And then it gets incubated together and we can see whether or not there is agglutination happening.

If there isn't any agglutination, then that's considered major cross match compatible and that might be the only one that you will do if you need to cross match any patient and be happy with that, especially if you're going to, to transfuse some. Some, red blood cells, but also if you send anything to a major lab or, or if you end up doing, doing that, you'll see also the results for the minor cross match, which is on the other hand, the donor serum, which is incubated with the recipient's red blood cells. Because inevitably even if you do give red blood cells, a bit of the donor's plasma is going with it because we can't just give red blood cells and as you've seen and as we've talked about the the PCV of the red blood cells will be of the red blood cell unit will be probably around 65.

That still means that there's 35%. Of of plasma in there so that it is still a liquid and not something extremely viscous. And so in that case, again, we put the recipient's rectal cells with donor donor serum, incubate together, and if there isn't any agglutination, then that is considered compatible.

And so that's what that's what it means when you get a result for a cross match that says yes it's major cross match compatible or it's minor cross match compatible or incompatible. What we're trying to do is figure out if there's gonna be a reaction inside the patient once we've given those cells, so we're getting a basically a small sample of. That putting them together and trying to see if there's going to be an issue and what we are then deciding on the result is if something is happening in the tube, then likely at a much larger scale, this is going to happen in the patient.

And so it's unlikely to work and that's what we call it incompatible. So we're trying to predict reactions really. So then that doesn't answer your question of like should I cross match, and the current guidelines are that for dogs, if they're transfusion naive and you know that they are, it is not mandatory, and, and you don't have to do it.

If there is prior transfusion history. It is mandatory if the first transfusion has been 4 days ago or longer than 4 days ago, because that gives them time to produce some antigens and the likelihood of reactions happening is higher after that time. So kind of like keep in mind this 4 days, especially if you are dealing with a dog with IMHA for example, that presents and they need several blood transfusions.

If they've been in your hospital for a few days, and you're thinking, oh, like when, when was the first transfusion? And again, when we were talking about which patients do I transfuse and when. It might be that you've got that IMHA patient in in your clinic and their PCV is dropping and you get them on the Monday and you give them the first transfusion on Monday and on Wednesday their PCV is dropping, but they're not quite at that trigger where you're thinking they're definitely again transfusion dependent and they need to transfuse them.

But you know that on Thursday you'll need to cross match and it might not be available to you or the number of units that you might be able to use might be much less than if you transfuse them on the Wednesday. And so again, that's when I always say the answer to do I transfuse this patient is always depends on the situation, because if you're in this situation and you maybe don't have many units that you can transfuse this patient with, then the answer is yes, transfuse them on the Wednesday before you need to cross match them tomorrow and and might not be able to use the units that you would have used on on Wednesday. So keep in mind that everything is depending on the situation and the patient.

And when it comes to cats, again, transfusion naive cats, it is not mandatory. However, it is a bit more recommended by experts, well, some experts, because there are some antigens that have been found on the surface of cat feline red blood cells. That are not of the AB blood type, blood group, like Mick, for example, which is not one that we can easily test for.

And so there is an argument to say that transfusion naive cats should be cross matched before before transfusion, even if it's their first transfusion. However, if you work in the UK, you might not have easy access to, feline blood or feline blood products anyway. And so personally in my practise, because of how difficult it is to to get feline blood, if the cat is transfusion naive, I will not cross match them because I won't have access to too many units anyway.

However, where it becomes strongly recommended and, and is becoming very difficult if you don't have access to feline blood products, but, if there is an unknown transfusion history, if there's been previous reactions, or if the patient has been transfused, and it's unlike dogs, it is 2 days or more before that second transfusion that you need to do, then it becomes really important to to cross match them and it is strongly recommended. So whether or not that means like getting hopefully several donors in if if you can do that. But, but keep in mind that that in cats, we say from the first transfusion if you have if you haven't cross matched two days later, you will, you will really likely need to to cross match and it is strongly recommended to do so.

Let's go back to Henry. We had, we had kind of like diverged about, and discussed a lot of other things, but, he's, we are still on Sunday night. His PCV is 15%.

As, as we discussed before, his physical exam, like he's a bit more, he's a bit less cardiovascularly stable that he was the day before. And, and I'm in a better place in terms of fluid overload and and how he is in himself to to transfuse him and for him to be able to receive any, any fluid therapy, which in this case is a transfusion. And I am aiming for a PCV of 30%.

So now it's Sunday night and I actually need to write on the transfusion sheet what I want him to have and how much I want him to have. And, just a a quick, kind of back to our agenda to make sure that we are following what we wanted to know. We've talked about how to recognise transfusion triggers and and who who we want to transfuse.

And, we've talked about how to choose the appropriate blood product. And so we said we are now in a position where we want to transfuse Henry. It's Sunday night.

He's having surgery tomorrow. Yes, we, we, we know this. This is why we want to transfuse him, transfuse him now.

We want to use some packed red blood cells for the reasons that we've discussed. And we know that he's not got any transfusion history. The owners do know that.

And so I, I'm not gonna need to cross match him, but I will, however, make sure that I've blood typed him. And, he is blood type A, as we've discussed. And so, now let's talk about how to do his transfusion and how to monitor it.

So, how much do I give? There's a few formulas out there that you can use to know how much to give. And if you're giving whole blood, the total volume to be given is usually 2 times the PCP.

Desired. So in this case, we want him to go from 15 to 30, so we want a 15% rise multiplied by his body weight, or 2 mLs of whole blood per kilo is usually said to raise the PCB by about 1%. Again, this, this isn't the case where we give whole blood.

Here I wanted to give him some packed red blood cells, and so the formula that I will use is the total volume of packed red blood cells that I want to give is 1.5 times the PCV rise desired, i.e., 15% times his body weight.

If you know the donor unit PCV, you can use the other formula that is there, which is the desired PCV minus the patient PCV. So again, we're talking about 15% here on the donor unit PCV blood volume and then body weight. And what I tend to use for a dog, blood volume is 90 mL per kilo and for cat it's 60.

So for Henry, as I said, we want, I've, I've used a formula of like 1.5 times 15, which is the rice that I want, times 5, he's 5 kg. That gave me 112.5 mL of, of packed red blood cells to give him.

For those of you who do have access to feline packed red blood cells, you'll know that they are quite small, that usually. About 40, 50 mL, if, if you're lucky and And if you do have them, so you can imagine in this case I would have needed at least 2 pipe red blood cell units, which using different donors increases obviously the risk of of transfusion reactions. And so in this case, and because Henry had never had a xenotransfusion before, we elected to give him a xenotransfusion, which meant that we could give him 112 mL of of dog red blood cells.

I obviously like. Like, quite like, well, I would like to talk about xen transfusions because we've had to use them and it's quite difficult to have access to feline products in the UK, and so some of you might be using them. If you have any questions about them, obviously feel, feel free to email me, but there are more and more like papers and, and reports about giving xenotransfusions, and they do tend to be safe as a first transfusion.

They should never be repeated. In terms of like how long do I give it over, again, we know that this little cat has been previously overloaded, and I'm about to give him between 15 and 22.5 mL per kilo, depending on like where I go.

If I go all the way to my 112 mL of blood, then that's 22.5 mL per kilo. So I'm going to choose a low rate to make sure that I don't overload him again and give him time to process and also.

I've got the luxury of time because I know that I'm on Sunday night and I've got until Monday morning that he's going to be induced to to give that that blood over. And so I'm, I'm gonna use that entire window really to make sure that I can give him a slow transfusion. And I'm, I'm gonna do it over 8 to 12 hours.

And to do that, I'm, I'm gonna have to like draw up syringes of blood in a sterile fashion to avoid any contamination. Because each syringe in the same way that each unit of blood that will take that you will take out of the fridge and hook onto a patient, shouldn't be out of the fridge for more than 4 hours. So if you do decide to give the a whole unit, Over to a patient by just taking the unit out of the fridge, it needs to be over 4 hours and you need to measure, like you need to give an appropriate rate of transfusion to make sure that that doesn't go over to avoid the risk of contamination.

And so as a result, I, I took like 40 mL per, per 40 mL of blood in each syringe, and then each syringe could be out of the fridge for for 4 hours each and then and then get the next one out, but it is really important to remember that that 4 hour rule for any unit or syringe that you take out of the fridge. And then monitoring the transfusion is really important, and we, this isn't in the hospital I work at, I work at at Dick White Referrals, and we use this, transfusion monitoring sheet where we're going to document everything that we need to know about the patient and, and where things are happening and to keep a record. As you see, we'll say, where the patient is, which blood product they're receiving, and, and that's when we're going to also decide that's when the vet will decide.

How quickly things need to go. It is quite common to start at an initial slow rate to be able to see if there's any reaction. There's no full on evidence out there to say, that it will prevent more reactions, but it is quite often that the initial rate for the 1st 15 or 30 minutes will be 1 mL per kilo per hour, for example, .

Or or sometimes 0.5 mL per kilo per hour, for 15 to 30 minutes so that we can see if there's any evidence of of reaction at the beginning. And then once we've reached that, usually it's in the comment section that the vet will say if there's not been any evidence of reaction, if there's not been any problem in that initial 15 to 30 minutes, then I want the rate to increase.

To this much for the rest of the transfusion. Again, if this number in terms of time is more than 4 hours, you need to either split the unit or have some syringes there. But altogether from the if you count the initial rate and the ongoing rates, all of this should be 4 hours if you're using a bag that you get out of the fridge and and that you're hooking onto your patient.

And then at the back of the sheet you'll see all the things that we are monitoring. So, pre-transfusion we'll get a TPR, we'll augmentation, blood pressure if needed, and then you get those 5, 1530 minutes. The first hour, there'll be more checks than then ongoing.

But you, everything will be written down here so that it can be compared, and if there's a problem, then that concern will be raised. And the reason why we do that is because we want to monitor for any incidence of transfusion reactions, and that's why our sheets will then say if you notice any of these things, then please flag it, let us know, and then we can make a decision. When it comes to transfusion reactions, what the reason why we're monitoring, these patients, tracks is your friend.

So these are the guidelines that have come out in 2020. The, full access in JVC, and they have three parts, they're a bit long, but I'm gonna try and like give you the highlights, in this talk so that you know what you're looking for and, and what to worry about. In terms of why do we worry, like, do reactions really happen?

Do I really need to monitor all of them? There's a, a multi-center study that's looked at, acute transfusion reactions done by, Doctor Hall, who's one of my colleagues at Dick White's, and, she's looked at the incidence of acute transfusion reactions in dogs and following the tracks definitions. And, .

She found that 8.9% of transfusions had like had acute reactions for when it came to packed red blood cell transfusion, 4 4.5% for plasma products, so it's less common for red blood cell products.

And same thing for cats, they also looked and found 7.8% for red blood cell containing products of acute transfusion reaction. And 1.1% for plasma products.

So not very common for plasma, more common, like around 8, 8% for cats and around 9% for dogs, but they, they do happen as a result and it is important to monitor those transfusions. In terms of like type of transfusion reactions that are there, there are the main way we categorise them is immunologic and non-immunologic ones depending on how like we think they happen in effectively in in the body. Acute or delayed, so acute is within 24 hours, delayed is past 24 hours, post transfusion.

And they all have like kind of like fancy names. The ones we are going to mainly talk about are the ones that are here, so febrile non-haemolytic transfusion reactions, FNHTR respiratory ones, they also have funky names, tad trali taco. The allergic ones, which are definitely not the most common ones, but I think the ones that people mainly worry about because it's kind of like the like spectacular ones, the allergic ones are like potentially could go up to anaphylaxis and and the ones we mainly maybe expect but not actually the ones that mainly happen.

The hemolytic transfusion reactions, and then some infections in case, in case there's been an infection in the bag and that we're effectively transmitting that whether or not it was present in the donor or if it happened in the bag after that, and citrate toxicity, . As well. So we're gonna cover those ones so that you're aware of them.

It doesn't really matter if you remember their name or not, but what matters is that you don't panic if you, if you do have a transfusion reaction and know what to do in in those scenarios. Again, tracks is your friend, and they have those algorithms for all the different, types of transfusion reaction and what to do if they happen. I appreciate you might not have the time to go through the paper if they were to happen, but hopefully you'll, you'll remember a bit of this.

So the most common transfusion reactions are febrile non-hemolytic transfusion reactions, i.e., your patient has a fever, like the temperature increases, during the transfusion.

So we are there in terms of in the tree in case you you got lost. So they are acute immunologic or not reactions. Again, the immunologic bit or not, you don't really need to worry about because at the end of the day it doesn't change what we do.

It's just for those of you who are wondering in terms of like what the process behind it is. The definition of a febrile non-heemolytic transfusion reaction is an increase in temperature above 39 degrees, and that is more than 1 degree from where you started. So if you have a patient recovering from GA and you're transfusing them and you start at 35 and they're suddenly 37, it's not a febrile non-hemolytic transfusion reaction because even though you've increased by 2 degrees, you're not above 39, and so.

Please do not stop any transfusions because your patient is now more hemodynamically stable and effectively that's why the temperature is increasing if they were hypothermic before, so it is important that it is above that 39 degree mark. They can happen either during the transfusion or within 4 hours of the end of the transfusion. They are not life threatening, and as you can see on, on this little diagram from a little on this diagram from tracks, you do not need to stop the, the transfusion.

You might want to pause it for sure whilst you're trying to figure out if it is a febrile non-hemolytic transfusion reaction and you're not seeing an increase in temperature because of other reasons, I, you don't want to have a fever and be like, oh, this is a febrile non-hemolytic transfusion reaction. I'm carrying on because I know that it's not a problem. You do need to rule out that there's not another.

That you are not facing a hemolytic reaction that also is causing a fever, that you don't have like a an infected an infection going on, for example, an infection in the bag, and this is why your patient's spiking a fever. But if you rule out these things and you end up knowing that it's a febrile, well, suspecting a febrile non-heemolytic transfusion reaction. You can restart the transfusion at the same or at a slower rate, whichever feels more appropriate at the time, and you can consider paracetamol obviously in dogs and not in cats to kind of of help with that with that temperature.

But the important thing is ruling out other things that will cause a fever before calling it and saying I'm good to continue and and not miss something else going on. Then there's a TA for transfusion associated dyspnea. So that's when your patient becomes dyspneic during the transfusion.

So it's acute respiratory distress. Again, this is during the transfusion or within 24 hours. And again you need to rule out all the other things, which we are going to talk about after, but namely tackle traley allergic reaction and pulmonary disease.

It's again a diagnosis of exclusion. And we like again, like, yes, if you were getting lost in that, little decision tree, and you do see a patient that has acute respiratory distress, and you kind of like look at the sample of of the patient to rule out any hemolysis. And if the patient is not showing any evidence of hemolysis, you can consider that it is dyspnea, like transfusion associated dyspnea.

If that happens, you do need to stop, and, and figure out what is going on because like it is obviously respiratory distress is is a is a big deal. And, and so these are one of the one of the ones where, where we say to stop the transfusion and, and like if if it's a big bag that you've just pulled out, put that back in. The fridge.

Once it's open, you can keep it 24 hours. If you were to find another reason or another recipient who who needs that unit, but it is important to, if you, if you don't want to like keep that clock going over those 4 hours outside of the fridge, then obviously try and and and keep that back somewhere safe. Taco, it's quite like a, a, a nice name, but it is when you get circulatory overload.

So again, as I was talking about Henry, a transfusion and blood product is another fluid that you might add to a patient who's already been fluid overloaded or who didn't have the capacity to take that much fluid that it needed. So these ones are non-immunologic. It's just that you increase the blood volume of the patient by giving more fluid.

And so that can cause acute respiratory distress and pulmonary edoema. This happens during or within 6 hours of the transfusion, and you can do all the tests that we had done for, Henry at the beginning when we thought he was fluid overloaded by checking the heart for, any left atrium, overdilation, checking for beelines, usually. They also respond to diuretics because again you're trying to like decrease their fluid overload, but it is it is recommended in humans to be cautious and not go as high as you would go for a congestive heart failure patient because they don't have the same response, the response, sorry, but you can give like 1 to 2 mixed bukego furosemide and see if there's any improvement.

So you do not necessarily need to stop from the transfusion point of view, but you do need to be careful and adjust the rate, and you might have to do what we've done for Henry of like drawing syringes and going at a very slow rate so you can continue to administer a product that effectively the patient might really need, but at a much slower rate so that they don't get fluid overloaded again. Trally for acute lung injury, so that's transfusion related acute lung injury, and these are also, like things that show up with respiratory distress, but in this case you don't get any signs of fluid overload, and and it's more an acute lung injury which happens related to the transfusion. So these ones are, immunologic reactions, and, and you'll get acute hypoxemia, with more evidence of rather than more cardiogenic edoema, which, which is what we would have gotten with taco, you get here non-cardiogenic edoema on on thoracic radiographs.

So these happen during or within 6 hours of transfusion. . And in terms of of like which patients you're you're looking at, these are the ones that won't have evidence before the transfusion of of lung injury, so we can say that it is associated with the transfusion, what happened, and, and these ones are not going to be responsive to furosemide because you're not dealing with a fluid overload.

So this is where we are in the, in our little decision tree, and in this case you must stop, again, like, like tads, these are the ones that, that you need to stop and, and see what you can do for the patient and manage the respiratory distress, put on oxygen, etc. And the ones that we are also maybe like quite familiar with are the hemolytic reactions. So the acute hemolytic transfusion reactions, these ones can be immunologic or not, and these are the ones that we're trying to kind of like foresee with our cross matches when when we perform them.

And so this happens when we get accelerated destruction of the transfused cells, and, and this is like for it to be an acute reaction, it needs to be during the transfusion or within 24 hours of the transfusion. It can happen obviously, when there's blood type incompatibilities, and that's obviously why we've been talking about blood typing and doing cross matches if needed. And, and so what you will see is a new onset of hemolysis within 24 hours or an inadequate increase in PCV.

For example, for Henry, we were hoping to get to 30% and then you transfuse them and, and you end up at like 1718. Clearly something's not quite right and some of those cells have gone somewhere, and they could have been acutely hemolyzed. They can be accompanied with, fever.

So again, make sure that you don't think that this is a febrile non-hemolytic transfusion reaction when you've actually got a hemolytic reaction. And if that happens, you must stop. Clearly the, the pro the product that you're giving is, is not compatible with the patient and it's, it's not going to reach the therapeutic effect that we are looking for.

You can also have those reactions in a delayed fashion, so you'll kind of have like similar signs, but instead of being within 24 hours of the transfusion, it'll be after and up to 28 days post transfusion. But again, this is the lysis of these cells that have been transfused that get with the delay, all kind of like destroyed. .

What you will be looking for is again an unexplained decrease in in PCV. You've initially had the good rise that you were looking for, for example, for Henry, maybe the day of the surgery, you do have your PCV of 30%, but then 3 days later or 4 days later, you've got a big drop that you weren't really. Expecting, so you might be dealing with a delayed hemolytic transfusion reactions.

It is typically what we tend to see with xenotransfusions, where the cats develop antibodies against the dog erythrocytes and then progressively destroy them, and you get those delayed reactions. The allergic reactions that I mentioned at the beginning are the ones that maybe we're like most aware of but are not very common, and these are immunologic ones. They happen during or within 4 hours of transfusion, and they are usually transient and self-limiting.

If you are, well, they are usually transient and self limiting, but they can go up to anaphylaxis. You can use antihistamines if they happen. Chlorphenamine is fine.

Do not use steroids and they, they do not help in, in those situations. If you are dealing with a real anaphylaxis, then obviously epinephrine is, is the one that you turn to. I, I'd hope that you wouldn't need to go that far.

They, they are very rare, these reactions, but good to know that if they do happen, then epinephrine is, is the way to go. If they do happen, obviously stop and assess. If it is a bit of like facial swelling or anything like that, it might be that you give chlorphetamine and then can carry on with the transfusion because it's self-limiting and the patient is fine.

Obviously if it's full on anaphylaxis, then do not continue with this. Citrate toxicity, obviously we put an anticoagulant in the bag, and that anticoagulant is going to go in the patient and it's going to bind calcium. That's how it anticoagulates blood.

And so you can end up with a patient that ends up being hypocalcemic if a lot of blood products have gone in the patient and effectively a lot of citrate has accumulated in the patient. Sorry. Which can also happen if they've got an impaired hepatic function because it will be the liver which will be in charge of metabolising the citrate that's been transfused.

Again, unlikely to happen if you're just dealing with the one patient who gets one transfusion, but it's good to know that it's out there and that if you suddenly get hypocalcemia after having, transfused a patient, then it's probably due to citrate and you can just supplement this, this patient with calcium. We usually say it's if the ionised calcium is less than 0.9 millimoles per litre, and.

You can, if you know that you're going to transfuse a patient with a lot of blood products, you can always like give some calcium as you're as you're giving the transfusions as well to make sure that you avoid this. Again, you do not need to stop, but you need to supplement calcium. Say we are hopefully quite done with our agenda.

I hope you feel that you now know how to recognise transfusion triggers, how to know how to choose the appropriate blood products, understand which ones you need to to pick and when it comes to to blood compatibilities and how to monitor the transfusion and and then if they do happen, recognise it and manage the the transfusions reactions we've we've just discussed. Just for a little follow up on Henry, he, he did very well altogether and he's definitely one of the wins of, of my residency. But, we started that xenot transfusion at 9 p.m.

On Sunday, at 9:00 a.m. On Monday, he was induced with a PCV of 30%, so we had reached what we wanted.

But in the afternoon he came back, from surgery with a PCV of 12%, so probably some blood loss during the surgery. Can't rule out as well that there was any acute hemolytic reactions happening with the transfusion. As I said, we do tend to stay to see delayed ones, but they can also be acute.

And he was quite unstable and, and for me had a lot of the transfusion triggers there. Thankfully we kind of like had prepared for this because if you were to, if if you are using xenot transfusions in your practise because of access, limited access to feline, blood products or no access to feline blood products. Be aware that you, you have, like a 24 hour window to, to give a xenotransfusion from when you start.

So if you say, like for example, you've given, we've given Henry something at like we've given the beginning of the xenotransfusion to Henry at 9 p.m. On on the Sunday night and he comes back at 2:00 p.m.

On Monday. Effectively I have until 9 p.m.

On that day to give him a bit more of that same unit of of dog blood. But you can have hemolytic reactions as early as 24 hours posting a transfusion, and there is some evidence that's coming out as well that they can have acute hemolytic reactions. So really, If you are using transfusions in your practise, please bear in mind that this could be a patch and that you could need a feline donor really soon.

Thankfully for Henry, this is what we kind of like had prepared ourselves for and and we had some feline donors lined up, to be able to to give him a feline blood unit. But effectively this is what happened in the afternoon after the surgery. He got some feline blood and obviously some type A blood at the time.

Never repeat a xenotransfusion after those 1st 24 hours from starting the first transfusion because they will be a lethal anaphylactic reaction in that case. So in terms of of reactions to to look for if you do end up using xenot transfusions, a paper that I published when I was at the RVC, looking at at at 49 cases that received a xenotransfusion. We, we had like 55, so the majority of cats needed a feline blood transfusion after the xenotransfusion, and it could have been like as early as 2 days after, but the median was 4 days after the initial transfusion.

And, and then there's another paper that's coming up obviously, looking at acute hemolysis in cats receiving xenotransfusions. And they, they did have like 18% of cats who didn't have any acute hemolytic transfusion reaction that still needed a feline transfusion, and their, their median was 2.7 days at the time.

And on the ones who did have a hemolytic transfusion reaction, 23% of them needed a feline transfusion, and that was earlier at 1.3 days posting the transfusion. Just be aware, if you use those immuno transfusions, keep in mind you might need a feline donor and you might need a feline donor very soon.

I hope this was helpful and that we've answered a few of your questions about transfusions. If not, please feel free to email me. Here is my email address.

And I will be happy to take any questions. And this is my cat, and I hope you appreciate how pretty she is. And, please feel free to email if, if any questions.

Thank you very much.