Hello, my name is Louise Southwood, and I am a large animal emergency clinician at New Bolton centre. I am going to talk to you about respiratory tract emergencies in horses. I'm going to start by going through upper respiratory tract emergencies, and then we'll talk about the lower respiratory tract.

And when we're talking about especially the lower respiratory tract, I will full declaration, I am not a boarded internist, I am primarily a surgeon, and so it is lower respiratory tract emergencies from a surgeon's perspective. So let's start with the upper respiratory tract. What are some of the things that might lead to a severe enough obstruction that the patient requires emergency care?

One of those is a snake bite, when they or any cause of severe swelling of the nasal passages or veneres, and it really has to be bilateral for that to cause complete obstruction. And one of the probably the more common things that We see here is a retinoid this is an example of a horse with a retinoid chondritis causing almost complete bilateral retinoid chondritis causing almost severe obstruction, but anything that occludes the pharynx or larynx can cause a respiratory distress. The severe cases of strangles can also call this as well as gutter or pouch tympani in young animals.

So they're just some examples of the types of cases we're talking about. When you have most of these horses, when they present, and sometimes it can be difficult to determine if it's an upper respiratory tract obstruction or a lower respiratory tract obstruction. One of the key things that you're looking for, however, is an inspiratory noise or an inspiratory stridor, which indicates the upper respiratory tract.

And and obviously it's Really, really important to differentiate between the two because one of the main procedures that we perform for an upper respiratory tract obstruction is a tracheostomy versus lower respiratory tract that's not gonna be effective. So when you're assessing these patients, look for the degree of inspiratory effort and also assess air flow through the nostrils as well. So like I mentioned, one of the main life saving procedures that we perform on emergency for upper respiratory tract obstruction is a temporary tracheostomy, and it can be really difficult to know.

Then when a horse actually needs it. So one of the criteria that I was always taught is if you're evaluating a horse and you think that horse might need a tracheostomy, then the safer thing is probably to do it. Other people make sure they're assessing, the horse at rest.

And if they're still making a noise at rest, when they're really quiet, quiet in a stall, then, then maybe a tracheostomy is required. My experience, however, has been it is much better to do a tracheostomy when the horse is reasonably. Rather than having to do it, when the horse is severely obstructed and down and thrashing around.

So I think this is something that's really important, to do as, as veterinarians, we should all be able to do this because as I said, this is a rapidly life-saving procedure and consider practising this on horses after they're euthanized. Necropsy cases, just so you can be familiar with the anatomy and the procedure. So the landmarks, it's the junction of the upper and middle third of the neck.

So what you do is you divide the neck into thirds, and it's performed right at this level here. If you do it too high, it's going to interfere when the horse venture. Flexes its neck, it's gonna interfere with the tracheostomy.

And if you do it too low, the distance between the skin and the trachea is too far, and you've got a lot of dissection, and then your tracheostomy tube is not really going to fit properly. So the junction of the upper middle third of the neck, and that's where you can actually feel the trachea the easiest as well. Go ahead and clip and prepare a large area.

Now, if the horse is is dying, has a severe complete obstruction, you've only got a couple of minutes to get something in, and occasionally with those horses, we don't clip. Prep and block, we just go ahead and attempt to get a tracheostomy tube in. However, in the ideal situation, go ahead and clip and prepare and then infiltrate the area with lidocaine.

Realising too once you infiltrate that area with lidocaine. You're gonna, it's gonna be harder to palpate on those tracheal rings. Go ahead and do your final prep.

You want to do, I usually do a longer incision than what they would do for a more elective tracheostomy. However, you can do 6 to 8 centimetre. Vertical incision.

If you've got a lot of experience with this, it can be smaller, but if you're in an emergency situation and you are not familiar with the procedure, go ahead and make a longer incision, get some better exposure. It's really important when you make this incision, you want to be on midline. If you get off midline, you're going to have to actually incise your sterno thyrohyoes muscle rather than dissect in between the muscle bellies.

And the other issue that occurs if your skin incision is not aligned with your tracheotomy incision, they can develop subcutaneous emphysema, pneumoedine and pneumothorax as a complication. So you want to be on midline, it's absolutely critical. If you're not familiar with the procedure.

Go ahead and make a bigger incision, 6 to 8 centimetres. And then hopefully if you're on midline, you should be able to bluntly separate between your sterno thyro hyoidus or yours what they call strap muscles. So once you get between those muscles, you should pretty much be down to the trachea, and then you make a transverse stab incision between the tracheal rings.

You do not cut your tracheal rings. The incision is in the ligament between the rings. The other thing that's really Critical at this point, horses do not have complete rings, and so you do not want to go more than halfway around the tracheal ring.

So your incision in the trachea should not be more than 180 degrees, ideally, about a third of the way around. And that's roughly 1 centimetre incision to the left and then one to the right. The other thing that's really important about this is you want to start with a stab incision.

Don't try and use the belly of the blade and cut, you know, to make your incision. What can happen is you can, without that stab incision into the trachea. You can actually push the mucosa off the tracheal ring and then you end up putting your tracheostomy tube in the submucosal space within the trachea.

It's in the trachea, but it's not actually in the lumen. So stab incision, go 1 centimetre in either direction, try to stay within 1/3 of the circumference of the tracheal ring and definitely not more than half of the circumference. The other thing that I do at this point because it can take a bit of an effort to get your tracheostomy tube actually inserted, and so I'll have a pair of Kelly hemostats available that I can put in between the tracheal rings and spread them apart to try and allow the horse to breathe and give the horse some relief.

So then you go ahead and insert your tracheostomy tube. You want to go, so there's several different types of tubes, you probably should have a couple of different sizes available and the one that's shown here is a silicon tube which is thought to be. A little bit nicer, more gentle to the soft tissues.

So go ahead and get that tube inserted. It may take a couple of attempts to get the tube properly inserted on the first on the first time that it does as you replace it, it does each day, it does get a little bit easier. The, so, and it takes quite a bit of force and quite a bit of effort to direct it between the tracheal rings.

One of the things that you have to be really careful about is make sure you do not put your tracheostomy tube into the subcutaneous space. I have actually seen that occur. Because the horse will still be obstructed.

So I mentioned a couple of different types of tubes. There was a silicone one, silicon J type tube. There's also a metal tube, which is probably a little bit easier to insert.

However, it is, it might be a little bit tougher on the tissues. There's also these self retraining, self-retaining tracheostomy tubes where you insert, one part, and then this threads through and then it locks in place, and they're a little bit. They're harder to dislodge.

They stay in place a little bit better, but once again they're metal. One thing is if you're using a J tube either one of these metal ones or silicon, it has to be secured really well to the horse's neck, and this is, this is just with gauze, and usually we do 2 to make sure that that tube doesn't slip out. And you can, if you're, if you're stuck or you have to anaesthetize the horse, you can also do a endotracheal tube as well.

So ideally, you want to have a kit available that is easy to grab in case a horse does need an emergency tracheostomy. Like I said in the beginning, it's actually better if you can do this on a sort of semi-emergent, urgent basis rather than as the horse is dying as it struggles to breathe. I usually start these horses on antimicrobials, we're violated part of the lower respiratory tract immune response by bypassing other areas in the upper respiratory tract, and often they need some sort of non-steroidal anti-inflammatory drugs, but that's kind of dependent also on the type of lesion you're dealing with.

You want to keep the tracheostomy site clean and this, this often requires some fairly aggressive cleaning, often several times a day, and you want to monitor the site for any signs of infection, which is mostly going to be cellulitis around the site. If the horse has a jugular vein catheter in, you want to monitor. Extremely carefully because they can get a septic thrombophlebitis if that tracheotomy site gets infected.

And so depending on what's going on with the horse, depending on how much difficulty you had performing a tracheostomy, you might want to put a lateral thoracic catheter in or something a little bit different. Than a jugular vein catheter, just keep that in mind. So infection can be prevented by obviously good aseptic technique and, and by keeping the site clean.

Watch out for emphysema, that tends to be more of a problem if your tracheostomy site does not, so the incision actually into your trachea does not line up with your skin incision. You want your skin incision. And your tracheostom are pulling the trachea to be perfectly lined up, because if they're offset a little bit, as the horse breathes, the air is going to get into subcutaneous space, and I did have one horse developed from the subcutaneous emphysema neo mediastin and a pneumothorax, so they do have to be monitored very closely for that.

So once the tracheostomy is in place, then you go ahead and make your diagnosis. And I'm not going to go into this a lot, obviously, endoscopy is probably the main thing that we do. This is an example of a horse with Well, actually, these are both horses with bilateral retinoid chondritis, causing severe upper respiratory tract obstruction.

And the other thing I'll show you some later is right-sided or bilateral laryngeal paralysis can also occur and I'll talk a bit about that. Also the radiography, to look for masses, ultrasonography, also to look for masses, any sort of retropharyngeal swelling that might be causing an obstruction, and then more advanced techniques such as CT MRI, and then haematology and biochemistry just to further evaluate the patient. This is a horse with gutter pouch tympani, and you can see it's causing collapse, severe gutter pouch tympani, and it's causing pharyngeal collapse and upper respiratory tract obstruction.

And this is a horse, this is radiographs, . And more advanced imaging and upper respiratory tract endoscopy and this was had a mass which was causing a complete obstruction or close to complete obstruction of the upper respiratory tract. So once you've got the patient stabilised, then you can go into further diagnostic tests.

Usually, usually you leave the tracheostomy in until, you know, the upper respiratory tract problem, is resolved. If you think, you know, based on the history that this horse might need a permanent tracheostomy, I think it's important to consider where you place your temporary tracheostomy because you don't want that to, in a With that down the road. Usually, once, once the problem is resolved, you usually remove the tracheostomy tube and you allow it to heal by second intention.

And once again, it's important at that point to keep it clean, and it may require cleaning several times, several times a day, but usually they heal absolutely fine. Once the tracheostomy tube is removed. So I mentioned, you know, several causes of upper respiratory tract obstruction that may require an emergency tracheostomy.

And this is, this is a, a cause that is not well described in the literature and it's bilateral retinoid cartilage paralysis. We most often see it associated with general anaesthesia. We had several of these when I was, actually I was an emergency clinician and also when I was a resident.

At Colorado State University, and I'll go through some of these cases and some of the key facts, but one of the things that it was likely a complication of is having a horse in dorsal recumbency with its neck and its head stretched out and potentially leading to damage to the recurrent laryngeal nerve and bilateral paralysis. The other thing, . The other thing that predisposes to any surgery that's performed in that neck region can also lead to this as well.

So it's something just to be aware of. This is just a case series that we had. One of the things you noticed there was a draught.

Breeds, some very large horses were overrepresented and two of these 9 horses were actually having larynoplasty and ventricular corectomy, so they were actually having surgery for laryngeal hemiplegia. A lot of anaesthesia duration was not necessarily long. However, a lot of the horses had hypertension, hyperventilation, or, relative hypoxemia under general anaesthesia, and you can see they were all in dorsal recumbency at some time, but the anaesthesia duration wasn't necessarily long in these cases.

One of the most striking things about this is the survival, unfortunately, was relatively low and some of these horses didn't, it, it wasn't that some of them died immediately from complete upper respiratory tract obstruction, however, some of them showed signs sort of several days later. One of the things that was most notable is the number of horses that had underlying laryngeal hemiplegia. And so they had left laryngeal hemiplegia as an underlying disease or they made a noise during exercise.

And so that probably predisposed these horses to this problem. And the reason I'm I'm presenting this is, it is very much underreported in the literature, and it's just something to be aware of when you're anaesthetizing a patient, particularly if you've have the patient endorsed or comes to try and make sure that that neck and head is not hyperextended and to try and take some pressure off the recurrent laryngeal nerve. So what do you We do for these horses, obviously if we could get them, we did a tracheostomy, sedation, is important, but we had some Saxonal crawling, close to the stall, so that we could inject them with this intramuscularly to get them to become recumbent, so we could reintubate them and give them an airway.

So what to do about this pre-op endoscopy probably is not realistic for a lot of these cases to determine if they have underlying life recurrent laryngeal neuropathy or left laryngeal hemiplegia. Like I said, avoid hyperextension of the head and neck during surgery, obviously maintain arterial oxygen tension and mean arterial pressure. And always recover the horses with either a nasal or oral and a tracheal tube in place so they at least have an airway till they're standing.

A lot of times these cases, we saw signs of the obstruction once they were standing, once the endotracheal tube was removed, and often it was associated with vocalisation, for example, when the was going back to the stall, so they'd vocalise, they would and then they would obstruct. And once they began to obstruct, as they took deeper breaths, they developed the obstruction persisted. If you have a severe acute upper respiratory tract obstruction, it's important to be aware that they can develop a negative pressure pulmonary edoema.

And so you notice, frothy fluid, coming from the nay. What do we do for these cases? Frizamide, Manitol, to try and decrease the edoema, corticosteroids may help.

Obviously, intranasal, oxygen, don't overhydrate them with fluids and ideally you'd ventilate these patients. some of them, I mean, this can be, this can be a fatal complication, . And some of them do respond to furosemide, manitol and corticosteroids, how it's a serious complication of severe upper respiratory tract obstruction, that, that can be fatal.

And basically it occurs when a horse takes a very forced, has a very forced inspiratory effort against a closed airway, there's a shift in pressure, a shift in the fluid distribution in the pulmonary parenchyma. Leading to edoema. So that's segues us into the lower respiratory tract.

I'm not going to really talk about negative pressure pulmonary edoema again. . But mostly what we're talking about here, and like I said, this is on an emergency basis, probably the most common thing that we see is pleural pneumonia or pluritis.

I'll talk a little bit about pneumothorax. I'm not going to talk a lot about hemothorax, because it's relatively uncommon. And pneumothorax is fairly uncommon as well.

Most of the wounds that I've had that have developed in pneumothorax, it's been relatively Relatively mild. So we're mostly talking about your pleural pneumonias, you know, you have severe pneumonias. So how do you evaluate these patients?

Often they'll present pneumonia or pneumonia, often they present with a fever, potentially a fever of unknown origin, they may have a cough and nasal discharge. However, I've had plenty of courses with fever, but without a cough, without any nasal discharge that have actually had pneumonia. So we need to be quite discerning, when you're evaluating these patients.

You can start with thoracic auscultation, however, in an adult course, especially one that's in good body condition, thoracic auscultation is, fairly, insensitive as far as diagnosing pathology. But basically, you're listening for wheezes, crackles, any dull sounds ventrally, any radiation of heart sounds can be one of the first indications that you have pleural fluid. And inaudible sounds dorsally can be consistent with the pneumothorax.

One of the things that I find much more beneficial than trying to escort the actual thorax is always listening over the trachea, because a lot of times you can hear fluid sounds. Over the trachea that you cannot actually hear over the thorax rebreathing exam is absolutely critical and this needs to be really done in a quiet place. Once again, you're listening to crackles and dull sounds ventrally, inorible sounds dorsally, that type of thing.

But when I'm doing a rebreathing exam, what I'm really paying attention to is how the horse behaves. Are they tolerating it well, and just taking nice deep breaths, or are they becoming distressed? Horses with pulmonary disease often become distressed.

They'll start coughing. They won't tolerate the rebreathing bag. Well, I'm not saying, you know, inexperienced horse that's sucking it into their nostrils.

I mean, you've got to be careful to make sure they don't do that, but, they truly become distressed, with the rebreathing bag. The other thing that I pay attention to with it is how many breaths it takes them to recover. Hor normal horses, they take a once you remove the rebreathing bag, they take a couple of deep breaths and they recover.

Horses that have pulmonary disease often take several more breaths and they'll be coughing and struggling with it. So that's an important part of the exam. The other thing is palpation and passion, and I saw a lot more for pneumonia cases, I used to be pretty good at identifying this, however, it does take, it does take quite a bit of practise.

And there's also you can pay attention to whether they're painful on palpation or the thorax. It can be a little bit difficult to assess, but it's an important part of the physical exam. So, the next, the next step, the next thing that we do at least in our hospital, is to do a transthoracic ultrasonographic evaluation of the lung surface, and I am not very good at ultrasound, but now, especially with these new point of care ultrasounds.

You can have an app on your phone and have a probe. It's making it much more easy to utilise. Like I said, I'm not great at ultrasound, but I can usually pick up changes in the lung surface that would make me think that this horse has pulmonary disease.

And this picture here on the left is a fairly normal lung surface. It's a little bit irregular, but it's not too bad. Sometimes, with early disease you'll see some comet tails and you'll see some consolidation of those comet tails, so you don't have this nice bright, fairly even line.

And then this picture here, on the right is, this is lung here and this is all fluid in the plural space and this is a, this is a large volume of fluid and usually you measure the fluid about how, how high it is, for example, above the point of the shoulder. So, like I said, I'm not an ultrasound expert, but I can, I usually have enough skill to be able to determine, you know, at least on an emergency basis, is there lung pathology, is there enough fluid in here that I need to drain the chest? So another thing we don't do is, is to consider on an emergency basis, we don't do this a lot in adult horses, it's more common in foals that look in very young animals to measure an arterial blood gas.

And basically what we're looking at here, when you get a blood gas, you get the pH. If the pH is low, if they're aidemic, if the pH is high, they're alkalemic. At that point, you you can look, you've got to determine what is the source of the asidedemia versus the alkalemia, and essentially you have metabolic causes and respiratory causes, and we're currently talking about respiratory causes here.

And to determine the respiratory cause, you look at the dissolved carbon dioxide in the arterial blood or PACO2 and if it's high, you have a respiratory acidosis, so if it's high, they're not ventilating well and if It's low, they have a respiratory alkalosis. A lot of times horses with pneumonia will be hyperventilating to try and increase the oxygen and so they may have actually have a respiratory alkalosis because they're hyperventilating, they're breathing more. The metabolic component is your bicarbonate concentration, which can actually be bicarbonate or you also see it written as TCO2.

And if bicarbonate is low, that's a metabolic acid acidosis and it's high, it's a metabolic alkalosis. And then what happens we'll talk about in the next slide, these compensate. So if you have a phosate, they do, they're hypoventilating and they have a respiratory acidosis.

The body can adjust the renal can adjust the bicarbonate concentration to compensate for that to try and maintain your blood pH. This is what this compensation looks like. So if you're, if you've got a really sick animal, and like I said, this is not going to be your average pneumonia case, but you've got a really sick animal and you get your blood work back, you're trying to work out what's going on.

So what, if you've got a respiratory acidosis. The bicarbonate should, in a normal horse that does not have a metabolic component, should increase by approximately 1 milli per litre for every 10 milligrammes millimetres of mercury increase in PACO2 above 40 millimetres of mercury. And similarly, for respiratory alkalosis, it should decrease by 2 millimoles per litre for every 10 mg, 10 millimetres of mercury decrease in PCO2 below 40.

So this just gives you some idea a little bit more globally of what might be happening in the horse. I mean, the main thing is to realise that the animal is basically compensating for many of these changes. And then chronic calculations are a little bit more different, but usually on Emergency, we're really talking about more of the acute, and these formulas can be found pretty readily in the literature.

So the other component of this, which is probably more important in horses that have, or, or really young animals. Adult horses, usually do OK is your oxygen content. And remember your PA02 is your dissolved oxygen in the blood, and your SAO2 is the, the satur.

Of your haemoglobin and remember tissue oxygenation or delivery of oxygen to the cells is dependent on your cardiac output, and it's also dependent on your oxygen content of the blood. And the key, the key things are determining your oxygen content of the blood is your haemoglobin. So if you're anaemic, you're gonna have low haemoglobin, even though your saturation might be fine, you're not going to deliver adequate oxygen to the cells.

And then also your SAO2 here, which is the percentage of that haemoglobin that's actually oxygenated. And a lot of times we look at PAO2, which is the which is the which is the dissolved oxygen in the blood, and even though it contributes very little to the total oxygen content, if you look at this as the oxygen haemoglobin dissociation curve, as that PAO2 starts to get lower, so around 80, your saturation begins to drop off precipitously, and that can definitely affect significantly your oxygen content of your blood and so. That's why, that's why we, even though it's a relatively small percentage of the total oxygen content, we worry about the amount of dissolved oxygen, because once that gets below a critical point, your saturation, starts to drop rapidly.

So like I said, this is more, you know, generally very sick animals. It's not common, that we need to look at this in adult horses with pneumonia, but it's good to have at least a basic understanding of it. So you've got a horse, said that maybe has a fever of unknown origin or presenting for coughing, nasal discharge, you evaluate it, you determine that it probably has pneumonia.

Excuse me, or, you know, pleur ammonia, my recommendation at this point would be to get a sample for transtracheal wash and fluid analysis. So, the other option is to start empirically on antimicrobials. However, if you look at the, the lecture on, any microbials in, you know, equine medicine, I think the more we can do to get a sample from the site of Infection, and while we might initially start on broad spectrum, empirical antimicrobials, once we get that culture and sensitivity back, we can at least make our antimicrobial a bit more targeted towards infecting organisms.

So how do we do this? How do we do a trans tracheal wash? And I have in the notes, it's a intraca, is what we use.

Basically, there's a needle and then a thin catheter, and, and, and it comes with it as a kit, and we use them. Mila, I believe, also has a similar product, . The site that you, so you want to have the horse sedated.

You want to make sure that you sedate the horse or that part of the sedation at least includes some buphenol, it's anussive, it's going to prevent the horse from coughing. I can tell you based on experience, that's an important part of the prep for this, and then you clip aseptically prepare the skin at the same location as the tracheostomy. You're essentially doing this at the same site that you do a tracheostomy.

And then you'll infiltrate the area with lidocaine. Obviously, you need a lot less than what you would need to do a tracheostomy, and you're obviously for tracheostomy and for this, you're gonna be wearing sterile gloves. Then you go ahead and insert a 1214 gauge needle in between the trachea rings and so you want to make sure that you have the trachea well stabilised with one hand and then you insert a needle, bevel down in between your tracheal rings and make sure you're on midline as well so you don't slip off the trachea going to the left, or right.

And then you essentially pass the catheter through through the needle into the trachea. These catheters, these intra cats have these bags on them and you can either do it with the bag, it might help keep it sterile, it does, you can see it bunches up, it does make a little bit awkward, and so you can remove the bag as well and just put the catheter through the needle. And so you're directing this down the trachea, towards the, towards the carina.

Once you have it inserted, and you have this set up ahead of time, you have about 3, 60 mL syringes filled with 20 to 30 mL of sterile saline, and you go ahead and you inject that sterile saline fairly quickly and draw back. And then you don't need a huge sample, you don't need to get all 2030 mLs back. Sometimes when you go ahead and wash, essentially you're washing the trachea, you go ahead and put the 30 mLs in, you draw back and you don't get anything.

That's why you want to have a couple of, a couple of syringes available so that you can, so that you can get a sample and the horse. Sometimes the horse will cough during this procedure. The main problem that coughing, does, even, even if you use butrophenol, the major, it can cause the catheter to retroflex back up in the pharynx so you can end up getting a pharyngeal sample, and you also have to be careful when you're removing those catheters, so that you don't, you know, cut them off with a, with a needle.

So don't. Forcibly remove them, just be gentle and ease the catheter out if that occurs. But most of the time you're going to get a sample, you only need a few meals, collect it for cytology, as well as for culture and sensitivity testing and put your sample in your culture vialcot and sensitivity testing first, and to make sure you don't contaminate it.

OK, and aspirate the fluid. And that's an example of a sample, that you might get, and this is just, an example of some cytology. You're looking for cytology, you're looking for the number of neutrophils, and you're also looking for a bacteria and a type of bacteria, and that can give you some idea of how you might want to direct your initial antimicrobial therapy.

But you're gonna start the horse on antimicrobials, a lot of times depending on the severity of the pneumonia, we start them on penicillin and gentamicin, pending our culture and sensitivity results. So that's a transfer killwah, mostly that is to be able to, #1, make a diagnosis and number 2, to try and direct, get a, get a culture and direct your animicrobial therapy. Occasionally we have to place a chest tube, and this is for horses with Pleuro pneumonia.

So they've got a significant amount of fluid in their thoracic cavity that they're unable to, they're unable to ventilate, they're having trouble breathing. And so, this is what you need for this, penetrated chest tube. Some, and then some sort of valve, to put on the end of it, ideally, some type of Heimlich valve, which is a one-way valve, or you can use, you can use a condom, or you can just get a glove, a finger from a glove and cut the tip off it so it doesn't aspirate air back into the tube and into the chest.

It'll just, it'll just allow the fluid to come out. So what do you do for this? I would do it recommend doing an ultrasound guided, especially with the ready availability of ultrasound.

So then you don't have to, to worry about hitting vital structures and you can, you want to get at the most ventral, the ventral part of the fluid as, as ventral as you can with the fluid to, provide adequate drainage. So what you do, clip, prep the area once again, you're doing this aseptically, go ahead, and infiltrate the area with lidocaine. You want to make sure, you know, the vessels and nerves run along the caudal aspect of the rib, so if anything stay towards the cranial aspect of the rib, to avoid those, avoid those vessels and obviously you need to avoid the heart and the diaphragm, but your ultrasonographic evaluation can help you with that.

You want to do a stab incision. I usually use the number 15, scalpel blade. One of the things that your stab incision, you wanna make sure it's deep enough.

You also wanna make sure it's long enough to accommodate the chest tube. So, I, I've seen that before you make the stab incision and then you gonna put the tube in and incisions not long enough. So you wanna make sure it's long enough to accommodate the tube.

If you're not doing an ultrasonographic guidance, ecostal space, eventually to the half of the chest, however, I think, in, today, these days, there's ultrasonography is, is sufficiently available that there's no reason to not do it ultrasound guided. As with a lot of things, and then you wanna go ahead and insert your insert your tube, and when you're doing it, you're gonna have to push really hard into what I do, and these chest tubes have, they actually have numbers in centimetres so you can see how deep you're going. Ultrasound can also help to tell you, oh, your fluid is, for example, 10 centimetres deep.

And then you go ahead and you're in, you gotta, you have to push fairly hard and so what I do is I have one hand, I have one hand in place to stop me pushing it too far and so you sort of have this as a, as a little sort of buffer or buttress to try to prevent pushing it in too far. And then once you get into the into the chest, you've got your tria in place, you'll see fluid, come back in the tube. You want to have a hemostat ready to make sure that they don't aspirate air so you can occlude the tube really quickly if the fluid doesn't come out, but most of the time the fluid comes out in fairly large volumes.

You want to secure the tube using a Chinese finger trap, suture, and you just want to, I, I collect the fluid in a bucket, so I can quantitate how much fluid I've actually taken off the chest. Now, if you think it's going to be a huge volume and the horse is sick, you should really make sure you've got venous access while you're doing this and potentially have the horse on some intravenous fluids, because you're taking, if you're taking a large volume of fluids off the chest, you want, you want to, you want to replace that. So once again, this is just a tube in place, Heimlich valve in place, and just collecting the fluid, in a bucket.

Sometimes they need a lot of times the pathology is bilateral, sometimes you can drain, both sides of the chest from the one tube. And so what I would do before I went ahead and placed the tube on the other side, I'd re-ultrasound, you know, the contralateral side, and see if I've collected fluid from both sides or just one. This is a picture of a horse that has multiple chest tubes in place, to get adequate drainage, and then, once it's, you know, if it's adequately walled off, which you can usually tell based on ultrasound and also the horse's clinical picture, you can go ahead and lavage .

The infected area, the plural space, the abscess, you know, to get it cleaned, to get it cleaned out, to get it underbred essentially. I usually don't do this on an emergency basis, I usually allow our internists to do that the next day. So this is just some data from a relatively recent study looking at factors that affect survival in 97 horses with septic pneumonia.

One of the things that's interesting, although that shouldn't really be too surprising for us, is about a third of the horses have recent travel history, and that's definitely a well recognised predisposing factor in horses with pneumonia and pneumonia. High creatinine concentration, which is probably just a measure of chronicity and how sick the horse is, increased the odds of non-survival, and it also increased the odds that the horse would not return to use. This was actually interesting to me and I know there's been some other studies looking at this, but in this study transtracheal wash fluid was more sensitive than pleural fluid for identifying the causative organism and actually I didn't mention that when I was talking about chest tube placement and that we really should have.

A sample of that for culture and sensitivity, but the transtracheal wash fluid was supposed to be more sensitive and obviously Streptococcus, strep equi subspecies zoo epidemicus is one of the most common organisms causing pulmonary pathology. This is, and I'm going to talk a little bit about this thoracotomy increase the odds of survival and so a lot of times these horses, if you know that placing a chest tube, allows drainage of fluid on an emergency basis, it can, it can help the horse. Be able to breathe.

However, if there's areas of abscessation, it's probably it's probably not going to be sufficient, and that's where thoracotomy comes into place, and I'm going to talk a little bit about that here in the next few slides. So, so this is just some complications, that can occur in horses with, fibrinous pleural effusion, and, you can see that, the complications, actually, not surprisingly, decreased survival, and these are the most common ones we, we see plural abscesses and we'll talk about that a little bit more. And when we talk about thoracotomy, laminitis is another common thing and so another common complication.

So a lot of times what we'll do is when we have these horses come in with severe pneumonia or pneumonia, we'll actually do digital cryotherapy to put ice on their feet to try and prevent laminitis, but obviously there's several complications that can occur. In these horses with fibrous pleural fusion, 60, 68% survived and to try and identify these horses and obviously the important part of the fibrinous part is, you know, it's less easy to drain, more likely to get walled off. They had a higher respiratory rate, a higher level of chlorophy, and remember I mentioned you usually measure it above the point of the shoulder, and more likely to have necrotizing pneumonia, more, .

Drains and they had a lower survival rate. So I mentioned thoracotomy. This is something that we are doing and by me, I, we, I don't necessarily mean me, a lot of times it ends up being my husband that's doing it, but people, I think, I get the sense that people are getting more aggressive.

About doing a thoracotomy in horses you do it standing and essentially what it is, is to drain those chronic, chronic abscess. So, you know, you've been treating the horse with antimicrobials, with draining the chest, and it's not recovering and there's in these abs areas of abscess areas of tissue necrosis, that have become walled off and a thoracotomy at that point, may be indicated. So ultrasonographic guidance is really, really useful and, and radio radiology as well, can help identify absences, but, ultrasonography can give you a little bit more directed approach of how to go, where to go with your thoracotomy.

So when do you do it? And there's been a couple of studies looking at this, This first study, at the median was 9 days, post-hospitalization in about 3 weeks, following onset of clinical signs, and this one here the the time to thoracotomy was 84 days. I think people are starting to do it a little more, a little sooner than later, but once again it's, it's kind of a big step and it's a reasonably big surgery.

So what you do, you can identify the site, based on ultrasound. There are a couple of different techniques. The technique that we usually use in our hospital is with a ribbrous section.

Some people, however, just, go in between, the ribs went in coststal through a. You can also remove the muscles and taking out the ribs and moving the muscles just helps to keep it open, the wound open for a little bit longer to allow draining. So you go ahead, the horse is standing, sedated, you want to provide local anaesthesia, you want to clip the hair aseptically prepare the skin and like I said, you can decide on the location based on ultras.

Gra ph y and also needle aspiration of materials to make sure you're selecting a site to optimise drainage. You want to avoid the inner coststal arteries and veins that remember run off the back of the ribs to stay away from them. So once you once you identify your site, you're going to incise over the size of the affected rib, you go through your skin, subcutaneous tissue and several other muscle layers, and then you go ahead and incise your your periosteum and elevate your periosteum.

As shown here and you can see the other thing that this picture, illustrates nicely, ultrasound has indicated, the cardiac, silhouette, so where the heart is, and they've also, outlined the abscess here, to identify the ideal site to go to allow for drainage. You want to go ahead, at that time and do a rib resection. Let me just go back.

So you isolate and transect the dorsal part of the rib with obstetric line. I'm going to show you a video in a, in a, in a minute. You go ahead.

And then isolate the rib, elevate the periosteum circumferentially, you pass your obstetric wire around the most proxable part of the rib that you're going to remove, and you're only going to remove a couple of inches, and then the ventral part you just articulate from the costochondral junction. You want to avoid the lateral thoracic vessels when you're doing this. Obviously you want to be ventral but not so ventral that you interfere with vessels.

And then, like I said, I'll show you a couple of videos of this. Once you've you've removed the rib, you're entered the space, you can lavage them, however, you've got to be careful because the horse, it can be irritating and the horse will start coughing. And for these procedures, it's also important that you provide adequate analgesia, and obviously, the animals are already going to be on antimicrobials treating the primary disease.

So this is what I'm just gonna read this. This is what this looks like, so this is just your obstetric wire or giggly wire placed around the rib, and then you're gonna disarticulate it at the costochondral junction. And then once you've entered the pulmonary space, that's when you're gonna start debriding your abscess.

So this is just removing all the pro material having enough that you can get your your fingers in and then a large amount of liquids coming out, so they're getting Fairly good debridement at this point, and this is obviously the, you know, this is obviously the fibrinous plural effusion that we're talking about, . That we were talking about that was described in that paper. OK.

And this is what it looks like at the completion of surgery, and as I mentioned, you can, you know, gently, conservatively lava that area, you can do ongoing debridement, you can also do endoscopy. To do further debridement and also to evaluate the tissue as well, and this is that same course, it just had the thoracotomy going in and looking at the surface of the lung, you can go ahead and pride, more of the fibrinous material, look for areas of necrotic lung that may need to be debrided. So how do these horses, how do these horses do?

The most common, the most common complication, and usually these are fairly well walled off and so this doesn't happen very often, is a hemi pneumothorax, and usually it's not, it's not significant and it's not problematic. And I think in one of these papers, none of the horses had problems with it, and it was a very small percentage and another one of the papers, local cellulitis. Can also develop, however, you just, you just want to keep the area clean and dry, abscessation at the thoracotomy site.

I think one of the two of the biggest problems that we see in our hospital is failure to resolve the primary problem, and then laminitis. And like I said, it's that whenever I have these horses come in on emergency, we usually start treating them with digital cryotherapy to put ice on their feet. So, Moving on, what, what is the survival, what is, what is the prognosis, how long does it take for them to heal?

It takes several months for that wound to heal. Usually the cosmetic outcome is satisfactory. 88% of the horses in this one study by Hilton at A survived to hospital discharge, and about half of these horses returned to their intended use.

And then this other study by Aoi, 82% survived at least two months, and the important thing is And these were horses just with septic pleural pneumonia, the thoracotomy decreased the odds of death, and it's like any like any tissue, any wound, going in and debriding necrotic tissue, allowing drainage is absolutely critical to resolve the infection. So the other, the other area to address on an emergency basis is pneumothorax, and like I said, this is, even with thoracic wounds, a pneumothorax that's significant enough that it requires, that it requires a chest tube placement. It's pretty uncommon.

A lot of times if you just seal up the wound really well, you know, pack it, put some, any sort of plastic wrap over it, ideally, if you can get an adhesive drape and glue that over it, it would help most of the time the horse can absorb the air and they're fine. However, if you do need to replace one, a lot of times what I end up doing is I'm not placing a tube per se, but using something like a tea cannula, so a blunt cannula and just sucking the air off, and that's often sufficient. We have obviously suction in our hospital, and so I'll just suck suck the air off the chest and then remove remove the teak hanger or whatever device I'm using.

There's also, you know, suction negative. Pressure suction devices, as shown here, that are available. Remember, the air is going to be dorsal, so you usually go in the dorsal third of the thorax as opposed to if there's a lot of fluid, it's ventral, and then you can also secure the tube in place.

However, in my experience, that's a fairly fairly uncommon event. So with that, I think the take home message of this is you know, as veterinarians, you know, upper respiratory tract obstruction is probably the, the most, critical and most emergent procedure you need to know how to do to give the horse an airway, and I think whatever opportunity you can have to practise that procedure, whether it's on a cadaver or, you know, just practise tracheostomy is really, really important to get familiar with the anatomy, and be prepared. Because it can even be, I, I, I've had horses die within minutes of obstructing, if it's a complete, obstruction.

So getting an airway is, is critical. And then another take home message too, if you've got a horse with lower respiratory tract disease, hopefully, you know, you'll be able to diagnose it based on your physical exam, your history, and ultrasonography can be extremely helpful, especially with new point of care, devices. And you're not necessarily looking at a, a lot of detail, you're just trying to get an idea of the degree of lung consolidation and pleural fluid accumulation.

Try and get a sample to direct your antimicrobial therapy. A lot of times we have to start these animals on broad spectrum, parental antimicrobials or even an antimicrobials, to begin with, but then having a sample available. You know, to make more targeted antimicrobial decisions, you know, after the first few days is really, really important.

And occasionally chest replacement becomes necessary on an emergency basis, whether it's for fluid, which can also include blood or air, occasionally we have to place a chest tube to allow the animal to be able to ventilate adequately. At that point, I'd like to say thank you for listening.