Good evening, everybody, and welcome to another Thursday night members webinar. My name is Bruce Stevenson, and I have the privilege of chairing tonight's webinar once again. I don't think we have any new members tonight, so the usual rules apply.
Questions into the Q&A box, come through to me, we'll hold them over to the end, and then Joanna has kindly agreed to answer those questions for us. So Deanna McBride graduated from the University of Sydney in Australia, where she developed an interest in emergency and critical care medicine. After several years in referral emergency practise, she undertook a residency programme at Murdoch University in Australia, which was completed in 2013.
She obtained her diploma with the American College of Veterinary Emergency and Critical Care in 2013, alongside a master's in Veterinary Medicine Science at Murdoch University. Duanna has worked at the Royal College in the United Kingdom for 5 years, and now she works at Southfields Veterinary Specialists. Duanna, welcome to the webinar, vet, and it's over to you.
All right, thanks everyone for joining us this evening. I'm gonna try to make this transfusion thing as, as enjoyable and it's as straightforward as I can, being a late Thursday evening. And if you do have any questions, I'd love to hear from you, towards the end.
So What I was thinking is like looking at a lot of movies and things about Dracula, you know, we realised actually blood is really, really important. And Dracula needed blood for vitality. And it's really, really no different to our, pets, our dogs and cats and why they need blood as well, including ourselves.
Luckily we don't have to bite people's necks like Dracula did to, get, blood transfusion, and we have a lot more sophisticated methods these days. So I'm gonna go to the very, very basics in why we need, why we need blood, and it's because we need haemoglobin to carry oxygen. So you can see here, I've just summarised the really long equation I usually have on my slides, but basically haemoglobin carries 4 oxygen molecules per haemoglobin molecules, and that's really important for oxygen delivery.
This is what I call the tree of life, basically stating that oxygen delivery with high haemoglobin oxygen oxygen, as well as our cardiac output. And our cardiac output is dependent on our stroke volumes times our heart rate, and our stroke volume is dependent on our pre-load, after load, and contractility. And often we measure our mean arterial pressure, which is dependent on our cardiac output and our systemic vascular resistance.
But what we're going to focus on is this component down here. So when we have no haemoglobin or very, very low haemoglobin, our, what happens is our oxygen delivery decreases. And that is what, and results in shock.
Basically, shock is anaerobic metabolism and what happens is then you have increased in lactate production, OK? So our body is really, really excellent in trying to compensate for reduced oxygen delivery even for really low PCVs. And so what happened is that the body is trying to improve the oxygen delivery when we're anaemic.
And one of the ways that they can do it is by increasing the respiratory rate and also respiratory effort in order to maximise the oxygen that the body already has. It also tries to increase our cardiac output, and it does this by, first of all, increasing our heart rate, and also it increases our contractility. So sometimes, you know, you feel those bounding pulses or the heart sounds just a little bit louder than you expect.
Sometimes what happens is if you have anaemia for quite a long time, the body thinks that it is in shock and tries to retain fluid. And when it tries to retain fluid or blood, it results in increasing afterload. So, this is sometimes important to remember Because it means that anaemic patients or chronically anaemic patients can be prone to fluid overload, particularly when we give a blood transfusion.
And I have to admit that I'm, I have, have caused fluid overload in patients from giving a blood transfusion. I'm sure I'm not the first person to do this. So, understanding the tree of life and how the body compensates for reduced haemoglobin delivery helps us understand what happens to the body when they're really anaemic and trying to compensate for that anaemia.
And that's really important to remember because it's related to what we call our transfusion triggers, which is our indications of when we need to give a blood transfusion. So some of these indications which I use clinically are, Increase in heart rate, so tachycardia, or sometimes bradycardia, especially if they're not compensating or cats like to do whatever they want, so sometimes they will become bradycardia. Also to remember that you can get arrhythmias, and this occurs because you have reduced perfusion of haemoglobin and oxygen to the myocardial cells, so you have abnormal myocardial conduction.
As I mentioned in the Tree of Life, that you can become more technique and sometimes more disni also. And as we talked about a little bit earlier about anaerobic metabolism, resulting in increased lactate production, you often will get an increase in lactate if a patient needs a blood transfusion on your blood gas results, or you may have a portable lactate monitor. So sometimes if I'm not sure if a patient needs a blood transfusion or not, I do run my lactates and that would also give me more evidence that I do or don't need to give a transfusion.
And finally, you can get reduced mentation because you also have, you also have reduced delivery oxygen to the brain and so reduce CNS function. I've also put here that it's a little bit hard to see here, but you can also get methemoglobinemia. I'm trying to describe brown mucous membranes here, and that is also an indication for blood transfusion.
You don't see these cases very often, but that's another indication, not just anaemia. So I'm gonna talk about the different transfusion products out there. And this is just a like very, very brief summary of what we have available.
So fresh whole blood, which contains red blood cells, platelets, and all clotting factors, and the main indication for freshhold blood is anaemia, plus or minus coagulopathies, and they've just put question marks from thrombocytopenia there. Store whole blood, includes red blood cells and all clotting factors except, factor 5 and factor 8. And so the indications are anaemic patients and vitamin K dependent coagulopathies.
So factor 5 and factor 8 are not vitamin K dependent. The ones which are vitamin K dependent are 79, 10, and 2. Unpacked red blood cells include red blood cells only, and the indications for for anaemia.
The autologous blood transfusion is auto transfusion also for anaemia. I'm gonna really quickly talk about Xenot transfusions later on this evening, as well as fresh frozen plasma and frozen plasma. So I'll go through those products in a little bit more detail.
So, threshold blood, by definition, is blood which is collected within the last 8, sorry, 6 hours and contains red blood cells, coagulation factors, and also platelets if it's at room temperature. I put it here in, as in room temperature because once the platelets are refrigerated, it becomes dysfunctional. So platelets are very, very sensitive little cells there.
And some people, I know some people do give the threshold blood in order to increase the platelet count, but I guess I'm in the camp that, It requires a lot of platelets to actually increase your platelet count, and most patients who are thrombocytopenic have ongoing thrombocytopenia due to new mediated reasons or even haemorrhage and increase in consumption, and that threshold blood really doesn't do enough to increase your platelet count. You can get platelet concentrates, But they're not very or pat patent rich plasma, but they're not really available here in this country. When we're thinking about freshhold blood, we need to think about how long it takes to get a blood donor in the practise, you know, how long it takes, and what is required to actually take that blood, and also the risk of a patient who is giving the blood transfusion.
So, although it seems like it's a great product because it contains all of these things, it, the practicality side of things is probably one of the most challenging. And I think that's why transfusion medicine can be challenging. It's not necessarily the medicine aspect of it, but com combine the medicine and what's actually practical and feasible within your practise.
So stored whole blood is red blood cells and plasma which is stored up to 21 days in the refrigerator. And it contains all coagulation factors except for factor 5 and factor 8. So it still has the vitamin K dependent factors.
And that's important to remember, say if you get a rodenticide intoxication resulting in coagulopathy and anaemia, you can actually use the stored whole blood, most of the time. Eventually, factor 5 sorry, eventually the, vitamin K dependent factors will potentially get Use up and there may be some benefit of using the threshold blood, however, most of the time you can use the stored product, and that will save you time if you've got product in your, in your practise already. Pack for blood cells that last a bit longer than the stored whole blood because of getting rid of the plasma.
And can last up to 42 days. It only has red blood cells, and one of the benefits is actually reducing, compared to say the stored whole blood, is that we're reducing the volume that we need to give in order to increase the PCB to the same value, which means that there's less risk of fluid overload. And as I mentioned earlier, these particular patients are at risk of fluid overload.
Some of the challenges we face is often in feline medicine, and we've, I think most of us will be using, a blood donor to collect blood. However, and particularly at that time, and that does put pressure, you know, on the patient waiting for the blood also puts pressure on all the staff in order to find a donor that can, that can be brought in at the correct time. And also kind of puts Pressure on that, that case and giving the, the blood as well.
And so, more recently there's been some other ways of actually obtaining stored blood in cats. This, particular website here, And there's associated paper publication that describes the efficacy of this and safety of these products, but basically it's a closed collection system of blood, so basically you can collect blood from cats in a closed collection system, and store it potentially up to 21 days. So then you've got like a more controlled method of collecting and delivering blood.
Rather than calling in a donor at an emergency. But I think, you know, what we need to think about if you are deciding to store feline blood is, you know, how often do you use it, and blood products are really scarce resource, and When we're giving a transfusion, you know, we really need to make sure we have the correct indications for a blood transfusion because, I know that it is a short, there are shortages, even from the various blood banks which are available. But I just wanted to show you this because it's a fairly new product and it's company, I think it's produced in Italy.
You can also get feline stored, blood from this, company BS animal in Portugal as well, and you can order that into this country also. The next one I want us to talk about is autotransfusion, also called autologous transfusion. And basically, I'm showing a picture here, I don't know if you can see, well, is that we can collect blood by doing abdominocentesis or thoracuscentesis, and here we're doing it ultrasound guided, or even in a sterile manner during surgery, using, suction, and collecting that blood and then transfusing it back to the patient.
The, with all transfusions, It's depends on how long the blood has been in the cavity. So if the blood is taken straight after a bleed, then potentially up to about 1 to 2 hours will have some coagulation factors still functioning there. So we should always use anticoagulants when we're collecting blood by this method.
It's also important to measure the PCV of that fluid taken. Just because it looks red doesn't mean it's blood. You may spin it down and just realise actually the PCV is only 7 or 8% and it may not be worthwhile transfusing that.
If we really need to ensure that the blood is no non-septic, so you might have a hit by car and have a heme abdomen, but, or, but we really need to make sure that there's no penetrating injuries into the abdomen. And sometimes just doing survey abdomen. Radiographs looking for free free gas in the abdomen could be a really good way to make sure that there's no perforation into the abdomen, clipping the abdomen while, making sure there's no wounds that you can see, which may be a source of contamination of intraabdominal blood.
Also, it's not recommended to transfuse neoplastic cells. A recent publication has shown that you can use a special machine called a savage salvage machine in addition to leukor reduction techniques to do that. But I think in if we're just, drawing it into a syringe and administering it, then we can't really get the neoplastic cells out.
So, xenotranfusion, I wanted to mention this. It's not something that I like, I highly recommend, but giving lectures on transfusion medicine, I've become aware that actually people have come across transfusions, sorry, xenotranfusions. So I just wanted to briefly mention this here.
This, picture on the left-hand side, I think is really fascinating. If you look very closely, you've got this man in the middle, he's sitting with both of his arms out, and you can see that there's this dog on the right hand side, that's hanging there, and you can see this frog going from the jugular. Into the man's arm.
And this describes the very first, xenotranfusion which was performed, many years ago. I've just, just lost exactly what year it was, but I think you can see from this picture that it's, well, it definitely wasn't in the last, 50 years. So, I think the first Xenotranfusion from, sorry, dog to cat, which is what we tend, not tend to do, but, would most likely do, that was first before, I think, approximately 40 years ago.
So these practises have been occurring, even dog to human, which is a little bit scary and disturbing. So I would recommend finding any source of feline blood, appropriate feline blood shower say, before we even consider resinno transfusion. And the reason is that, a, the risk of transfusion reactions is higher, and in recent publications, there's actually been several publications about xenotranfusion from dog to cat, but some of the published complications include tachychnia, jaundice, pyrexia, hemoglobinuria, so that's from hemolysis, acute or delayed, and as well as death.
And you know, one of the benefits of cat to cat transfusion is those red blood cells will last about 30 days, but when we give a xenotranfusion, the lifespan of those red blood cells is only on average about 3.6 days. So if you think about like if you've got a cat with IMHA and you're giving a blood transfusion, and you're starting the immunosuppressive drugs, those immunosuppressive drugs might not even kick into about a week.
So even if you give the xenotransfusion by day 4, that patient might become anaemic again. So that's why we highly recommend giving cat to cat blood transfusion and avoiding xenotranfusion as much as we can. And I think with the more widely available feline blood products, I think it's less likely that we need to give a xenotransfusion.
The really important thing is to never give a xenotransfusion twice, because that would definitely kill a patient. So next, I wanted to talk about plasma products. So fresh frozen plasma, it has all clotting factors.
And by definition, fresh frozen plasma is, blood which is separated, the plasma is collected, and it's frozen immediately up to 365 days, which is a very arbitrary number. Frozen plasma is basically the same product, but it's gone past that 365 days expiry and will last up to 5 years. It's also been shown that if you, I wouldn't say accidentally, but we all have those cases where, you know, we're ready to give a plasma transfusion, and then for some reason, the, the client declines to, to give permission for the transfusion or the patient's passed away.
And we've got this product that we've just defrosted, you can refreeze it. And when you've refrozen it, then it's called frozen plasma. And studies have shown that the the clotting factors, or the vitamin K dependent ones are still present, but not factor 5 or factor 8.
One thing to remember is, you can get, fresh chosen plasma for cats, and with cats it has to be types specific plasma. When we separate the pla the red blood cells, from the plasma, They basically, the product, I think it's from BS Animals is, if you go on their website, it's really, really detailed. Pet Blood Bank also have a really detailed, website that has lots of useful resources of blood transfusion, but they say do use type specific blood because they can't guarantee that.
All the red blood cells are separated and there might be some very minute, remnants remaining. So, and with the risk of transfusion reactions with incompatible blood types in cats, you know, the risk is much higher, of a transfusion reaction. So always use types specific plasma for cats.
So the indication for for plasma products is coagulopathies and the dose we use is about 10 to 20 mL per kilo, which I think is also a fairly arbitrary number, but that's a published dose range. I tend to only give the plasma if there's evidence of bleeding or if there's a risk of bleeding. We do see many patients who have a prolonged PT and APTT, but they're not anaemic.
There's no evidence of bleating and there's no risk of bleeding, and perhaps, treating the underlying cause may, may be sufficient. But if there is bleating or risk of bleeding, for example, gastric ulceration or future planned procedures, then, plasma products are indicated. They, I know a lot of people use plasma products in very hyperinemic patients.
And in my practise, I tend to only give these, products for hypoalbuminemia if they're really clinical for that hypoalbuinemia, for example, if they're hypertensive, or if they're so low that I'm concerned about wound healing. There are, I just wanted to mention, if you have a patient who's hypoalbuminemic, there are other resources as well, and nutrition is a really good resource for increasing your protein count. There is a recent publication looking at, the use of, plasma products, and basically, I've just summarised the results into this space, this one liner here, but looking at the study, it showed that roughly about 30 mL per kg over 12 to 24 hours, so different animals, it was more of a retrospective study, so different animals received different volumes over different time frames.
Just summarising the results, roughly about 30 mL per kg had resulted in approximately increasing albumin of about 10 grammes per litre. But it really depends on why the patient is hypoalbuminemic in the first place. So, it, it is, it is possible.
In humans, what they would use is, humans. Serum albumin. And that is sometimes available, but can be a a bit of a scarce resource.
And also we are giving a xenotranfusion and there is higher risk of transfusion reactions if you give human serum albumin. And it's also very, very expensive. So, look at these resources first.
So I wanted to talk about blood types, and with canine blood types, they are multiple different ones, DA1, 3457, da, K1 and K2. We only test for DA1 as DA1 positive or negative because that's really the one that has been shown so far to be strongly antigenic and at risk of causing serious blood transfusion reactions. About depending on the, the breed, the location, approximately about 30 to 60% of dogs DA1 test positive, which, and that's looking at different studies, the rest are DA negative.
I think we tend to come across more DA negatives than positives. DEA negative dogs are a universal donor, meaning that we can give this blood to a positive or a negative dog, but shouldn't give a DEA positive positive blood to DEA negative unless, you know, if he really needs to, and it's the first transfusion reaction, sorry, first blood transfusion because there's no naturally occurring antibodies in dogs. However, with cats it's really important to give type specific blood because it has autoantibodies.
And so the feline blood types are the ones that we test for are A, B, or AB blood type grouping. There's also the MEC blood type as well, which, depends on what study you look at. Some think, some studies think it causes some transfusion reaction, but it's not something that we test for commonly.
Depending on what country or what area you live in, Type A is the most common blood type. Type B can occur anywhere between 5 and 36%, but depending on the country or area you live in, and type AB is very rare, looking anywhere between 0 to 14% of cats. And you can see here that, you know, type B will have anti-A antibodies, and, vice versa for type A.
This table just summarises things fairly simply. So we've got the blood types on the top here, and then the antigens on the red blood cells will be an antigen for type A, B antigen for type B, and A and B antigen for type AB. The antibodies in the plasma of type A cats will have majority weak anti-B antibodies.
There depends on the study, some studies show that there are a few cats. One study showed up to 20% of strong and TB, . Antibodies, majority, I would consider weak anti-B antibodies.
So that's important to remember. Type B cats have strong anti-A, antibodies, and that's important to remember when we're thinking about what blood we should transfuse to a type AB cat. And Type ABs have none.
Your donor type 4 type A should be A. Donor bloody 4, type BAs should be a type B cat, and ideally for a type ABA, we shouldn't have a type AB donor. However, as I've shown in the previous slide, the prevalence of type AB cats ranges anywhere from 0 to 14%.
So you'd be very lucky if you can find another AB cat. So because the type A cats have weak anti antiB antibodies, that would be the next most ideal blood type to give, and never give type B blood to a type AB cat. When we're doing blood typing, the old traditional method and it's it's still available and much cheaper is the, the blood, type card, but more accurate, particularly in cats with or dogs with auto agglutination is the, the cartridge type here.
And so you can see you've got the control here, and this is a type AA, so there's two different products which are widely available, and they work in a very similar manner. Cross-matching, so blood typing we always do. Cross-matching is, looking at the reactions from the donor red blood cells, the recipient serum, which is a major cross match.
Or we can do a minor crossmatch. So that's the donor serum to the recipient's red blood cells. So if we're giving a red blood cell pack for red blood cell transfusion, the major crossmatch is the most important one, for example.
So the indications of performing a crossmatch is that they develop antibodies at least around 4 days after the first transfusion. So if we give, say if we've got an IMHA patient, we give a blood transfusion on day 1. And then 2 days later, that dog becomes anaemic again.
You can still give the type specific blood type as a donation without doing a crossmatch. But if we're starting to look at day 4 and 5, then we will need to perform a cross match. I also try to get a good history from the patient, so if the patient has an unknown transfusion history, and you don't know if they've had a transfusion previously, that's an also important time to perform a cross match.
For dogs, all compatible, sorry, for dogs, all crossmatch have been shown to be compatible in transfusion naive dogs. And so therefore, a crossmatch is only necessary for a second transfusion after 4 days of the first transfusion. However, with our feline patients, they showed that not all, only about 60 to 85% of cross matches in transfusion naive cats were compatible.
So the verdict's out there, should we perform a crossmatch in all of our feline patients even for the first transfusion? So there are studies kind of looking at this, if I'm gonna reverse the data a little bit, basically studies have shown that they are incompatible crossmatched results in cats who've never had a transfusion before. However, despite having these incompatible cross matches, they still received a blood transfusion, and about 10% of them had a febrile transfusion reaction in non-crossma cats, so not a serious transfusion reaction.
They also looked at the difference in PCB, between the crossmatch and non-cross-match, cats, and the reason that they're looking at the PCB is they're looking for evidence of hemolysis. So, you know, how long the PCV stayed at the ideal number for, and they basically said that there was no difference in post-transfusion PCV in the crossmatch and non-crossmatch group. So, I think looking at the these type of data, some people argue actually we don't really need to perform a cross match if Pat has never received a transfusion before.
And the other thing is, remember I mentioned earlier, the challenges of transfusion medicine is not just the science or the evidence-based medicine, but also the practicalities. So let's say we perform, let's say, OK, let's try to do the very, very gold standard and cross match all cats, even if they've never received a transfusion before, and you get an incompatible crossmatch. What are you going to do?
Are you able to get another, cat in to donate some blood? Are there any other resources of, red, red blood cells? You know, if that is not practical and they've never received a blood transfusion before, perhaps the best option is actually just do the blood typing and don't worry about the crossmatch.
Also, when we're thinking about cross-matching is how do we perform the crossmatch. And there's this rapid the H test here, and I, I've used it, it's very easy to use. I've had some excellent results from it.
And as you can see on the left-hand side of this is, from a particular paper, it shows that you've got a positive cross match on the left-hand side where the red blood cells are floating at the top. So these are glutinate red blood cells, and you've got a negative cross match on the left on the right hand side, sorry. So, and so they're your controls, and this is the actual patient.
So you can see in this patient, there's a little bit of kind of hemolysis in the plasma there, but you've got a negative cross match, so that's great. But what they found is they got a lot of results kind of floating around in the middle, and how do we interpret them? And then one particular study showed about, you know, 50% of these cross-match tests has resulted in these kind of ambiguous results.
So, Saying that, I have used, used it very successfully. The times where it might be a bit more challenging is if there is auto hallucination, for example, in IMHA, patients. However, I've had good results in IMHA patients as well.
So it may be worthwhile trying. But if you are getting ambiguous results, it may be worthwhile sending it off to the lab, where they do the gold standard method of cross matching. The challenge of that is that you'll get your results 12 to 24 hours later, depending on how far you are away and which lab you use.
And so sometimes when I, when I'm thinking about a transfusion, I might preemptively send the cross match test off to a lab if I'm really worried about the patient might needing to get a transfusion. So it might be, you know, Tuesday afternoon and you Like, OK, the PCB is dropping, doesn't need a transfusion now, but I'm worried he might need a transfusion tomorrow. Let's just send the crossmatch tests up this afternoon, and then hopefully we'll get the results back tomorrow morning in case they need that transfusion.
So that's kind of how I plan my day. So, in regards, we'll talk about blood donation next. So we need to think about the, blood donors, OK?
I guess, more commonly these days we're doing, donations, from collections from cats, but we do for our adults as well. So they need to be healthy, obviously, a good temperament, for cats, ideally a body weight greater than 4 kilogrammes, and dogs greater than 23 kilogrammes. They need to be up to date with vaccinations, flea control, and worming also.
And also not received any medication within the last 2 weeks. And the criteria is also an age between 1 to 8 years of age and no previous transfusion history. We need to perform a pre-transfusion screen, so that's a full physical examination.
Annual haematology and biochemistry and testing for infectious diseases, FIV, FELV and mycoplasma in cats, and in dogs, 4DX and angiotroylus in this country. How frequently do you perform those tests? It would depend on how often the, the cat might go outside.
So, my cat was a donor. He was an outdoor cat. Every time, he, I, he donated, which was probably too frequent, but it was often the most available cat.
But I always did FIV, FALV, for him. Some people do perform echocardiograms in CATs because of potential underlying myocardial disease, which may be non-clinical, but that's, totally up to you and if that's available to your practise also. I would say majority don't, but I know some practises that do.
The ideal PCV is greater than 30%, but ideally higher if it's, if it's possible, and of course blood typing. So with our little feline patients, it's really important, and this is for our dogs as well, but I just think more so in our cat, they're just such sensitive creatures. But when they come in, bring them into a really quiet room, make them nice and.
Excuse me, make them nice and comfortable, as you can see in the picture on the left hand side. When you're, you know, when you're examining the patient, keep them nice and comfortable. And if what I do is preemptively before putting IV catheters or taking any blood samples, is placing M cream on local anaesthetic on the, the leg and putting a little, You can use cling film or any kind of wrap it over it and just leaving it there for about 40 minutes, that's how long it would take.
So that will give the cat time to relax and chill out and make themselves at home. There's actually not that many papers on sedation protocols for giving a blood transfusion, and this is just one of the very few, which is actually quite a while ago in 2010. But one of the protocols that they use is ketamine, buttrophenol, and midazolam, preferentially over inhalational, sedation because there's less risk, of adverse effect to the cardiovascular system.
What is not recommended as aceramazine because it can cause hypertension, and we are removing a large blood volume, but the other thing, it also can cause platelet dysfunction. This is a nice little paper that was published from the Royal Veterinary College, that looks at the unexpected events during collection of blood donations in cats without sedation. And so basically they looked at about 46 cats in this retrospective study, and 8 out of those 46 cats required extra sedation or or sedation full stop.
And so it shows that actually if we keep them nice and calm, use things like ELA cream. Select the appropriate donors as a blood donor, then we don't even need to give it to patient. When we're collecting blood with our dogs, we use this human collection system, and it's already primed with anticoagulants there.
And the donation volume is 450 mLs, and that's because it gives the correct ratio going into these bags, which is why we say they, the dogs need to be over 23 kg to safely donate. In cats, it's a little bit more challenging. Luckily we've got this new clothes collection system.
If that's going to be easier for you to collect blood and give it straight away, that's a great system to use, or you can just use like a 3 syringe method of blood collection. The volume to collector is about 10 to 15 mL per kilo, which usually results in about, you know, 50, 50 mL of blood. So the ratio of the anticoagulants to the blood is 1 mL of anticoagulant for 8 mL of blood.
And what I tend to do is just draw out the anticoagulants from one of those, human bags into a syringe, or you can purchase, one of these collection systems, which has anti I think that's the anticoagulants there already, inside the system. We, if it's if we need to administer immediately, we should do that within 6 hours, or you can store up to 20 days in a closed collection system. When we're administering the blood products, first of all, we need to prescribe how much blood we want to administer.
And this is an equation here, the desired PCV minus the patient PCV divided by the donor PCV. All of that multiplied by the volume, multiplied by the body weight. The desired PCV is is.
The number out there is 28%, and that number of 28% comes from human studies showing that it provides the most adequate ideal PCP necessary for stabilisation. And actually, if we increase the PCV too high, not only are we giving more volume, so risk of fluid overload, more antigenic stimulation, but increasing red blood cells also increases the viscosity and also reduces the flow of blood. So 20% is perfect.
The blood volume in a dog is anywhere between 80 to 90 mL per kg, sighthounds, greyhounds are up to 100 mL per kilo, and blood volume in a cat is anywhere between 40 to 60 mL per kg, so they're the numbers to plug in there. If you can't be bothered doing that calculation, anywhere from like 1 to 1.5 mL per kg of packed red blood cells will increase the PCV by 1%, and 2 mL per kg of whole blood will increase the PCV by 1%.
So they're kind of much easier mathematics to perform, particularly if you're really busy in a stressful environment. This, little paper came out this year. It looks at all transfusions in 8 cats.
It's a retrospective study, and I think this paper nicely shows that 1 meal per kilo of blood collected, from, I think most of it was the abdomen, but I think there were like 1 or 2 cats, we collected from the test, I think, has increased the PCB by 1%. When we're administering the blood, we usually give it at a slow rate at 0.5 to 1 mL per kg per hour for the 1st 15 to 30 minutes, and then 2 to 10 mL per kg per hour and to complete within 4 to 6 hours to minimise bacterial contamination.
I do like to use syringe drivers, particularly in our small patients, in our cats. And also make sure you use the philtre when we're administering the products. So you can either use these philtres which you can purchase separately, or you can get the giving sets which has an inbuilt philtre in it.
Sometimes you might want to consider giving as a slower rate. For example, if there's some degree of cardiovascular compromise, as I mentioned, fluid overloads the risk, if the olli or auric renal failure, so you're worried about fluid overload there and chronic anaemia, also risk of fluid overload, you may want to give your transfusion over a longer period of time, if you, you can split the blood products and it lasts you up to 24 hours in, in the fridge. The opposite is if they're dying before your eyes, then you may need to give the blood products much more quickly.
So this particular patient turned up into the ICU where it had severe haemorrhage through its gastrointestinal tract. That presented hypovolemic from dehydration and also very, very anaemic. And what we had to do is, he was becoming more and more bradycardic.
I thought he was going to die within minutes, so we just basically abolished the pack for blood cells there, as you can see. When we're monitoring for these patients, we need to make sure we keep a very good monitoring chart, and that's also details of the donor and the recipient as well. So if there is any transfusion reactions, we can record that appropriately.
And you can see that we're, we're recording, you know, the rate, the heart rate, respiratory rate and temperature and potential other findings there. When we're monitoring, we're monitoring because they're at risk of transfusion reactions. And I like to divide it into acute immunological reactions, acute non-immunological reactions, delayed immunological reactions, and delayed non-immunological reactions.
And as you can see here, the acute immunologic reactions include acute hemolytic reactions, acute febrile non-hemolytic reactions, and acute urticaria. The acute non-immunological reactions can range anything from non-immunological hemolysis, so they're like shearing injuries to the red blood cells, electrolyte disturbances, and often that's secondary to the anticoagulants that we're using. So it can cause hypercalcemia, hyperkalemia, and hypermagnemia, and that's also due to red blood cell destruction also.
You can get air or blood clot embolism, endotoxic shock if there's bacterial contamination, fluid overload as we already mentioned several times, and also hypothermia for administering blood products we called the temperature the room temperature. You can, the delayed immunological reactions include a delayed hemolytic reaction, so that stays later where the PCB starts to drop. And also post-transfusion per which we can be up several weeks afterwards.
The delayed non-immunological reactions is basically the infectious disease transmission and I hope we can prevent that by doing the a good pre-screening. If they do develop a reaction, stop the transfusion immediately. Perform the PCV in total protein and a blood smear of the donor and the recipient.
And what we're looking for is bacteremia, and more so in the donor, but have a look in the recipient and also evidence of hemolysis, particularly in the recipients, but look in both. If they develop hypertension, dyspnea, bradycardia, we're worried about like anaphylactic shock, you can give adrenaline. If they develop a febrile non-hemolytic reaction or acute urticaria, then we can go chlorophenamine and restart the transfusion at a slower rate, or you can get, if there's still an issue, you can get a new bag of blood products.
I've just popped this here, which is a, a really, really excellent blood transfusion book if anyone is interested in further reading. It's an excellent publication, so I highly recommend this. So, that basically concludes this evening's lecture on transfusion medicine, and I'd like to welcome any questions if anyone has any.
To honour that was absolutely fabulous. And, as always, the best specialists always make these things sound so easy, until we're in the situation of doing it. Just, as a heads up, your xenotransfusion that you were racking your brain, was the first one in 1671.
0, thank you. I knew it was like a long time ago. Yeah.
Yeah, yeah. No, neither. I cheated.
I looked it up. OK. just a question for you.
When you're doing your monitoring of your transfusion patients and that sort of thing, at what point do you become concerned? I mean, is it a, a percentage of heart rate and respiratory rate and temperature or one more than another? That is a good question, I don't have hard and fast rules and figures.
I think it's also really patient dependent, if the temperature goes like one degree higher, then I would start to, Consider stopping it and restarting it at a slower rate. If we're looking at respiratory rate and the heart rate, if I think it's a significantly increasing heart rate, it's difficult to give actual numbers, but also thinking about, are there any other reasons why that heart rate has Your respiratory rate has gone up or gone down. So thinking about that as well.
I think if you've got, if you get tachycardia to the point of, you think it's shock type tachycardia, so depending on the size of the dog, you know, they go up to like 160, 180, you know, I'd definitely be concerned there. And significant bradycardia in cats as well. The other thing to think about, like when you do see those changes, you want to assess the whole patient as well.
So you might need to start thinking about, OK, maybe let's look at the membrane colour, what's the memmentation like, you know, what's the pulse quality? You might want to just check your blood pressure and just do a global survey of the patient as well. And that might give you an idea of, you know, if you should be worried or not.
Yeah, so it's an overall package rather than a single parameter. Yeah, yeah. And I think that's, that's, like anything, I think in, in emergency medicine as well.
You know, when I'm thinking about is a patient in, why is a patient tachycardia, is it in shock? But, you know, think about other causes of tachycardia as well. Yeah, yeah.
Excellent. Well, I think you've covered everything. Certainly, we don't seem to have any more questions.
So I think you've given everybody a lot to think about and certainly, covered all the, the, the normal questions that we have when we're dealing with these. So it's up to me just to thank you for your time. And it was great to welcome you onto the webinar vet, and we look forward to having you back again in the future.
All right. Well, thank you for having me and thank you everyone for joining me this late Thursday evening. Have a good night.
Folks, that's it from another Thursday night members webinar, to dawn my controller in the background, as always, a special thank you and to everybody for attending. Thank you very much. We'll see you on the next one.
Good night.