Hello everybody and welcome to this webinar on pre-anesthetic assessment of the small animal patient. In this webinar, we will be discussing preoperative assessments in our patients, any further diagnostic testing that may be required for them, and also how we can use all of this information to support our clients, gain consent, informed consent, and also manage their expectations. Starting with consent, it's very important.
There are some differences in the law. We can get consent for a procedure that needs to be performed, otherwise, we do run the risk of something called trespass, where we haven't given them informed consent about what we are about to do, and we are just going to do it without their knowledge. We do have a duty to inform clients of the risks as well that their patient may be put in front of.
Otherwise, if we don't, we do run the risk of having to provide compensation, so that would be financial compensation to the client, but we also do run the risk of reputation ruin as well. There are two different types of consent. We have got that consent has been implied, so this could be during a physical exam when the owner brings their pet in.
However, no risks have specifically been explained. We've just implied consent that, oh, can I just take them out the back and just get this done. I think I will have a nurse hold them, for example, because they may be a little bit stressed.
We don't have, explicit consent in this manner, but we have just implied consent when the owner goes, OK, that's not a problem, you can take my cat or my dog out the back. We then also have express consent. So this is what we need to obtain for any procedure that carries a risk.
So this can be verbal or in written form, and we must allow clients to reflect on the information that we have given them. So it is essential that a record of advice offered is made and that consent has also been granted. So this should be written in the case notes for that patient and their clinical history with a time and a date as well that can be referred back to.
While written consent is not strictly necessary to defend an action, it will provide evidence that consent was actually obtained. When we have an animal in front of us, it's really important that we confirm with the owner in front and also the team out the back, the patient signalment, their clinical history, the reason for the sedation or the general anaesthesia general anaesthetic procedure, and also we have summarised the relevant clinical history and the medical history for that animal. It's really fundamental that we spend some time with the owners and ask particular questions in the consult room to try and gauge how happy, healthy, any change in health trends that that animal is going through, versus just saying, are they happy and healthy at home, you know, we really should hone down and ask them specific questions.
So, it should be questions around like when did the animal last have something to eat. Have they had any previous anaesthetics, even if they are a client of yours? Have they gone on holiday and had any kind of anesthesias or anything to report following those anesthesias if they've been in a different practise?
Any known allergies, any previous or present diseases, just to confirm that you and the client are on the same page, that they fully understand. The disease process that is going on with the animal. Are they on any treatments?
Has there been any vomiting or diarrhoea recently? Has there been any signs of difficulty of swallow swallowing that's going to give us an indication on perhaps if there's anything stuck in the oesophagus and also give us an indication about how, patent their airway is. And finally, specifically focusing again around that airway is has the, has the owner noticed any coughing, sneezing, or breathing difficulties.
It's always interesting sometimes when you do prompt an owner with these types of questions, where you do pick out little tidbits that perhaps they were never going to say until you really do probe them. When it is time to perform a physical exam, we must recognise that this is one of the most important tools we have. So, let's take the time to do this physical exam.
It's not just a checklist. The outcomes and the findings of this physical exam will directly influence our anaesthetic plan, the drug choices that we use, and overall and ultimately, it will impact patient safety. So first, let's start with temperament.
This isn't just about how well we'll be able to handle that patient. It will also affect how much information we can gather from that patient and how we then approach premedication. So, for example, a very anxious or aggressive patient may require heavier sedation, but that could actually mask underlying issues and or also impact their cardiovascular stability.
So we always need to balance safety with diagnostic value. Next we have a body condition score. So obese patients, they can often have this reduced cardiovascular efficiency and function, and they are also more prone to hypoventilation under anaesthesia.
So not only do we have a problem with carbon dioxide level regulation, But it can also present airway challenges as well. On the other hand, very thin or very cathexic patients, they can have less physiological reserve and are at higher risk of hypothermia and also hypoglycemia. So the patient with an abnormal body condition score is going to be more or less sensitive to particular anaesthetic drugs.
Next, let's have a look at hydration. So, assessing hydration is critical. Even mild dehydration, this can reduce circulating volume and lead to poor tissue perfusion, especially during anaesthesia, not just before we take them into the theatre.
Hydration issues as well, this will also contribute to electrolyte imbalances. So, where possible, we should correct dehydration before the anaesthesia, especially if we have time. So, especially in the cases that are elective.
We then assess the cardiovascular and the respiratory system together. We're listening for heart murmurs, for arrhythmias, assessing pulse quality as well at the same time. And if we find any abnormalities, this is our flag to potentially postpone, even if just by minutes or hours, the procedure and gain consent for any further investigations or modifications to our anaesthetic protocol.
On the respiratory side, we're not just oscitating that thorax, we're observing breathing pattern and also effort because subtle changes, really subtle changes, can indicate an increased anaesthetic risk, particularly when it comes to oxygenation and ventilation. A lot of our patients are very good at masking these issues, so we do want to take some time and try and recognise any subtle abnormalities. Neurological assessment.
So, finally, we should do a brief assessment of the central nervous system. We want to know if the patient might be more sensitive to anaesthetic drugs or if there's potentially some kind of underlying neuromuscular disease that could affect respiration. We've got to try and make this clinical picture fit.
So, even simple observations, just as simple as mentation, gait, or just general responsiveness to you talking to that patient, this can be very informative. It's important to remember that these findings don't exist in isolation either. So for example, an obese patient with a respiratory compromise carries a much higher risk than either factor alone.
So we are trying to integrograte our findings together to build this complete picture of the patient. And every single abnormality, even if it's just a gut feeling that we have, this should influence our plan. So this might be just a change in the drugs that we choose.
It could be escalating the monitoring level, or it might even be as drastic, if you like, as delaying the procedure itself. So the physical examination we do on our patient, this really is the foundation of a safe anaesthesia experience for our patients. The goal isn't to find the perfect patient that we are going to anaesthetize.
It's to understand the patient in front of us and understand enough as well that we can anaesthetize them safely too. If you do need any help making protocols in your practise on things that you want to ensure, get done, more of a checklist type of thing, we can refer to the BSAVA manual of canine and Feline anaesthesia and analgesia, and we can break down as well in chapter two, these particular guidelines on, specific areas that we can concentrate when taking a patient history and also doing that physical examination. So we can use this.
This graph, if you like, that is in this book to try and implement protocols and make SOPs in our practise. Once we've completed our physical exam, the next step will be deciding whether we need to do further, testing. So, importantly, this isn't a checklist for every patient.
So not every single patient is going to need every single thing on this list. Testing should be guided by our clinical findings, the signalment of the animal, and also the procedure that we have planned. So for many base, for many patients, we can start with this basic screening test.
So this could be the patient that's just going up under a routine procedure if you like. So maybe your everyday healthy scale and polished patient, maybe your bitch bay or your, canine castration. We can still consider some basic screening tests for these patients.
It could be pack our volume, total solids, you know, this is quite inexpensive. We can run electrolytes if we're concerned, and we can also take a blood glucose measurement too. So they're quick.
They are not expensive to do, and they can help us identify any common issues like dehydration or anaemia or potentially even a metabolic disturbance. We can also have a look at renal function by completing, urea and creatinine. So these are particularly important for some of our older animals, and maybe less so in our younger animals, but if we do get that feeling that there could be something wrong with their kidneys and even their liver, we can do some basic testing there as well.
Having a look on the metabolic and the endocrine side of things, blood glucose will be really, really useful here, especially in our small, young, critically ill patients. Hypoglycemia can develop so quickly under anaesthesia, and it may not always be clinically obvious without testing. So these 4 points here, these are our nice kind of basic testings, really quick to do, really cheap to do.
Then we can move on to some of our more advanced testing. So we can have a look at coagulation profiles and liver function too. So, in patients that have suspected liver disease or maybe we're going to do a more invasive procedure, we should consider coagulation profiles and liver function tests.
These will help us assess both the bleeding risk in our patient. And also the patient's ability to metabolise anaesthetic drugs. Ultimately, most of our drugs undergo hepatic metabolism.
We can also perform urinalysis, so this will provide valuable additional information to everything else that we've done. Especially in animals with suspected renal disease or otherwise quite significant systemic disease. Often it's underutilised and we think, oh, why should we do a urinalysis in a patient when we've done a, perhaps a kidney profile and a liver profile, but still they can significantly enhance our assessment too.
Looking at more advanced diagnostics additional to our lab testing, we can do radiography, we can do ECGs, and also perform an echo on that patient too. These should definitely be considered when there's abnormalities detected on the physical exam or in the history that has been given by the owner. So for example, this could be a heart murmur that may warrant undergoing a cardiology assessment and doing an echo.
It could be an arrhythmia that has been, newly oscultated and therefore we want to perform an ECG on our patient. And also, if we have a concern about the patient's respiratory function, this will also justify thoracic imaging too. So, the key point is that testing should be targeted.
Over-testing is definitely unnecessary, but under-testing may mean that we miss important risk factors as well. And this is also supported by evidence that I've shown here on the slide. And this study highlights that greater attention to correcting pre-anesthetic abnormalities can reduce the risk of anesthetic-related morbidity and mortality.
It's really important for us to identify and address these issues before they become critical in the procedure itself and even into the recovery period. When we have a look at our SEPSAF study, so our big morbidity mortality study, where the data capture is still 20 years old, however, it's still one of the biggest studies that we have to date. When we have a look at, the risk of anaesthesia in our small animal patients, it's still quite high.
And when we compare this to studies previously, in the decades beforehand, we're not really changing too much. So we still have quite a lot of room for improvement. This study, this found that one in 600 dogs, so 0.17% of dogs undergoing anaesthesia will die from an anesthetic-related event.
So not something surgical. It's not going to be, OK, we cut through a major vessel and that patient bled to death. It is more around something that we did with drugs or perhaps we weren't monitoring them.
It flagged up that we're still losing quite a lot of our patients. 1 in 600 dogs. Now, this is across all health categories of patients.
It obviously does get lower, that, that number does get smaller, the healthier the patient is, but still, overall, 1 in 600 dogs and 1 in 400 cats will die from an anesthetic-related complication. This study here, this is a UK based study. And, like I said before, it is already 20 years old from its data capture.
So its data capture was done in 2002 to 2004, and it was published around 2007. But when we still have a look on a global scale at all of these other, parts of the world that are still having morbidity, mortality events, actually, when we have a look at the numbers, they're quite high. So, we do know we are doing a good job in the UK and that ultimately comes down to this progression of our industry, especially nurse focuses, around patient monitoring and then passing that information on to the vets.
It also comes down to the fact that we have got better monitoring equipment, so we have those dedicated nurses. We have this monitoring equipment that can highlight issues, and we also have continuing education on making anaesthesia safer for our patients. But when you do have a look at some of these, studies, and they are still, you know, quite recent, these are still in the last 10 or so years, some of these numbers are still quite shockingly high.
Like, for example, in France, so it's the 4th 1 down on the mortality in dogs. 1.5% of dogs in France were dying from an anesthetic-related complication.
And then when we go down to mortality in cats, we do have a smaller data capture done by Redondo Eau, and we can, it's, it's a smaller data capture than our big SIPSA study, but we can still see here over 2% of cats were dying in the anaesthesia specifically, around a complication that potentially could have been avoided. Now I want to take a step back and have a look at the bigger picture. So let's have a look at morbidity and mortality in human anaesthesia.
So in human medicine, in human medicine, sorry, anesthesia-related morbidity, and mortality is extremely slow and it's low, sorry, and it's often quoted to be around 1 in 100,000. And when you look at a morbidity mortality in human medicine, even if you are not going in medically minded and you are going in as a A non-medically trained person and you Google this type of thing, you will actually get all of these resources that flash up that have been provided by the RCOA specific to the UK around what can happen, where the risks actually lie, and also, you know, that statistic is right there in front of you when you are a human undergoing an anaesthesia. Now, the, the great thing is, is that it gives us in veterinary medicine a benchmark to work towards.
We know we have got massive advancements in human anaesthesia, human medicine, and, of course, very individualised approach to anaesthesia. So that helps us, take stuff forward into veterinary medicine. And what we can also see is that they have highlighted over decades where things have popped up and where things can improve so we can optimise these systems and ultimately make anaesthesia safer.
And I do really believe if we were to do that data capture from the SEPSA study, if we were to do that again 20 years later, I do feel confident we will definitely see a change, unlike the preceding decades beforehand. Here's just another one of the, documents that can be given to you when you are a human undergoing an anaesthetic. So, this one here just discusses these common events and risks in anaesthesia.
So, the consent and the, implied consent and all of the information and the discussion of risks, this is really in-depth discussed in human anaesthesia, but maybe less so in veterinary medicine. One thing that was quite interesting with the human side of things was they came up with a plan and a project to improve. How could they improve human anaesthesia.
So we have to remember that in veterinary medicine our risks are ultimately higher just because of the slight delay in some of the up and coming technologies and also the consistency between practises as well. But the principles for improvement, these are still the same as what we can find in human medicine, and that's ultimately what the slide is going to focus on. So.
First and foremost, when human medicine wanted to improve their morbidity and mortality statistics, they looked first of all at identifying high risk patients, and it sounds really straightforward, but it's really challenging. There's multiple scoring systems and different approaches that can be used, and these are often based on comorbidities and surgical risk as well. We have adapted one of the, the human.
Systems into veterinary medicine. So that's our ASA grading system, which I'm going to talk about next. So that's something else we've learned from human medicine and we're taking on board.
But ultimately, they started with scoring systems, different approaches, standardised approaches that were based specifically on comorbidities. And more recently, there has been a shift towards assessing physiological reserve, actually. So not just what disease the patient has.
But how well they could tolerate any additional stress, and I think this is really important. I still think in veterinary medicine we focus on comorbidities, but perhaps not necessarily about the reserve that that patient has left, whether it's quite a lot of reserve or not much reserve left, and how just that simple anaesthesia that we think might just be warranted or needed so that we can do a scan and polish, etc. Might just tip our patients over the edge.
They also try to improve the preoperative assessment. So once high risk patients have been identified, then we can act on that information. So we can improve preoperative assessment, triage, preparation.
This is all key. We've got to optimise the comorbidities, correct dehydration, and assess nutritional status as well. So this was all done in human medicine.
This is stuff I really do believe we can start implementing in veterinary medicine. And importantly, the processes, these aren't just happening at referral or high level hospitals. This should be done everywhere and and anaesthesia is being performed in human medicine, and I do think that is the same thing we should be applying to veterinary medicine too.
The patient doesn't need to be treated differently just because they are in a referral setting. We can optimise the patient's safety, the assessment that we do, the stabilisation that we do in our general practises too. Of course, outcomes don't just depend on preoperative assessment and then all of the blood tests that we do as well.
It's worth noting that while all the testing I've just previously described is important, it should be used carefully as well, because quite interestingly, in human medicine, overtesting can be driven by Medico-legal concerns and cost, and it might not always improve outcomes. So, a lot of the time, some unnecessary testing is done in human medicine just to save themselves, just to be sure that if anything happens in future or if anything happens postoperatively, they are protected against lawsuits and insurance payouts. But ultimately, not a lot of these things were actually changing findings, and there was a massive cost to the NHS, so public health and also private health as well.
And fundamentally, we as, as people are the are the ones that are paying for that. So we can definitely transpose that over into veterinary medicine. Let's be careful with how much testing we're doing because, It should be warranted.
It should be warranted against that clinical exam. There are costs associated. It may not always change the anaesthetic plan, but we could change, you know, that extra 50, 150, 200, 500 pounds that that client has to spend on their pet when nothing else, it doesn't, you know, we don't gain any, any newer information.
Looking back at that SEPSA study, when we have a look at all of the things that can go wrong in a patient's anaesthetic experience and things that we can change, it is ASA status. So just grading our patients highlights morbidity, mortality risks, having a look at procedural urgency and also procedural complexity, looking at the age of the patient, assessing their reserve of the organ systems that may be affected with age. Looking if that patient's obese and of course identififiable factors, quite interestingly when we look at the SEPsA study also include things such as if we intubate a patient, especially a cat, and they are at higher risk of morbidity mortality and also in cats as well, if we provide them intravenous fluid therapy, they're more likely to have a morbidity mortality event.
So when we look at these identifiable factors for where our patients get into trouble, there's a large group of them that we can look at before we actually anaesthetize them. Maybe we can stabilise them a little bit more. We can get their organ function, their reserve capacity increased for those organ systems.
They can go on a diet. They can improve with exercise, their cardiovascular health and stability. These things with the ticks next to them.
This is where we can improve our patients' anaesthetic experience before their anaesthesia. So, let's break these down. Let's have a look at ASA status.
So, one of the most widely used tools in pre-anesthetic assessment in both human medicine and also veterinary medicine is the ASA physical status classification. So, this gives us a simple, structured way to assess risk based on the patient's overall. Health.
And so what does it reflect? At its core, an ASA status will reflect the patient's pre-anesthetic health, particularly the presence and severity of any systemic disease that they have. It's not about the procedure that they're undergoing, it's about the patient.
You can have a healthy patient. Undergoing quite a massive procedure. The ASA status is about the patient, or it could be a patient that does have a lot of comorbidities.
They are at higher risk undergoing a simple procedure such as a scale and polish. That scale and polish doesn't lower that patient's risk of morbidity mortality. It's the Health of that patient themselves.
So we have to look at comorbidities, and a key part of a sign in the ASA grade is identifying these. So they may be obvious. It could be something like cardiac or renal disease or it might once again be very subtle.
So something that is potentially early metabolic or endocrine disorders as well. And if we can recognise these conditions, they will help us plan an anaesthesia more safely, particularly when it comes to drug selection, monitoring of that patient, perioperative support, and how we can plan the recovery period as well. So let's briefly walk through ASA grades.
So, ASA grading is done from grade 1 all the way up to 5. So ASA 1 is a normal healthy patient. ASA 2 is one that will have mild systemic disease, and this may be a controlled.
Patient that, is on medication for a significant systemic disease, but if it is, well-managed, then this could be classified perhaps as a mild systemic stable disease. Interestingly, brachycephalics fall under ASA 2, even if they're healthy. They are never going to be an ASA 1 because there's fundamentally, something wrong with their airways and because of that type of confirmation, There is stuff that affects them right down to a cellular level.
So brachycephalic patients, they're always going to be an ASA 2 or above. We then have an ASA 3 patient, so this could be moderate systemic disease, this could be stable or unstable. ASA 4 is severe systemic disease, and ASA 5 would be this moribund patient, a very, very high-risk patient.
And then we add E for emergency onto the end. If it is a procedure that is coming in, That we haven't necessarily planned for. This could even be a patient that comes in to have a, you know, a stitch up post running in the park where they've cut their paw.
Essentially, this is deemed as an emergency because we are doing it on the day and we're not able to necessarily take weeks to stabilise them if they need. So an E just is what is added to any grade just as something, that is classified as emergency, kind of like on the day procedure. And what's the link between ASA grading and risk?
So, importantly, as you can see here, as ASA grades increase, so does the risk. And this has been demonstrated by multiple studies, including the, SEPSA study that I've once again referenced here. So, let's put these numbers into context.
For example, in dogs, mortality will increase from around 0.05%. In an ASA 1 to 2 patient to over 1% in ASA 3 or above patients, and we also see a very similar kind of trend in cats too.
You can tell just by moving up certain categories that there will be this significant change in the level of risk as well. So, one important, thing to consider is that the ASA grade as well is not fixed. The grade can change within hours depending on that patient's condition.
So, for example, with fluid therapy, with stabilisation, We can shift that ASA grade down, or if that patient further deteriorates, then their ASA grade can also increase and move up. It should always be reassessed. It may be something that is assigned first thing in the morning and then when we move to do that patient's procedure in the afternoon, their ASA grade may have shifted.
So it's really important that once again we assess the grade before anaesthesia. ASA, it's very useful for communication as well and general risk kind of stratification for our clients. It can help them understand what their pet is going to go through.
Of course they're all worried. They've heard horror stories, they've googled things. It can help to either calm them or just manage their expectations.
It doesn't account, however, for every single factor. It is specific to patient health. So it does not factor in things such as surgical complexity or specific physiological derangements.
We can just see that a patient might be, moderately systemically, insulted or severely systemically insulted. So, it doesn't always, Account for every single factor that that patient's going to be put through. So we should, should align our ASA status alongside clinical judgement as well.
But overall, ASA status is a simple and effective, powerful tool for us. As a veterinary team to identify risks, to communicate risks within the team, to try and plan for those things and guide our planning as well. It isn't just about assigning an ASA number.
It's about understanding what that number actually means for our patient. Long gone are the days where we've been left in the dark about trying to assign ASA grades as well. I know that this is fairly new, that people are implementing in practise, or maybe it's the first time you're hearing about ASA grading, but thankfully, Durox, so they were the people that made alfaxalone before it went to Zoeis, they made a nice, printable.
Chart on different ASA grades and you can find here this on their website, if you or if you just Google, ASA grading Durox Alfaxan, it typically shows up. So you can see here, we've got an ASA physical status too, so that patient with mild systemic disease and the animal is compensating. These are our low-risk patients, and then we move.
Into our high-risk patients as well. So you can see here under our ASA 5, we've got advanced or decompensated cardiac disease. We've got DIC, we've got GDVs, we've got multiple organ dysfunction, severe trauma, shock, malignancy, metastatic disease.
We can try and grade our patients. And then if you're unsure, What to do with that grade, once you have appreciated, OK, I actually have a patient that is higher risk, now what, how shall I manage them? Well, thankfully, if you can reflect back, if you've got access to the BSAVA manual of canine and feline anaesthesia and analgesia, and if you flick to chapter 13, there's actually a really useful group of tables which, Assign different premeds and considerations depending on the grade of the patient for both cats and dogs.
So it's a really good starting point if you're unsure about where to go with the grade that's, that's in front of you. And just to finish off talking about ASA grades, we know that they work in human medicine. We have tried to implement them in veterinary medicines that we can improve this communication between a team and also managing expectations and outcomes with our clients.
We now thankfully, because it is such a new topic, there is a lot of evidence that has come out and some nice studies and some nice papers. So I just wanted to go through just briefly the outcomes of some of these papers around applying ASA status. So, This particular study, this, the conclusion for the study was that ASA grading was a valuable prognostic tool and is recommended to identify an increased risk of morbidity and mortality.
In this particular study as well, you might not think that a patient presenting for a, for a, a fracture that has been sustained by trauma. Might be actually a high-risk patient. You just think, OK, well, they've got a broken bone, but when we break down as to when that bone broke, did it break days ago and that patient just hasn't come home, so therefore they're dehydrated, etc.
When this particular study had a look at different ASA grades of fractures, they identified in a lot of them over 50. 0% of them were automatically in this higher risk category just from this bone fracture. So you think, OK, a lot of bone fractures, they're typically happening in our younger patients when they're being, you know, they're running away from us in the park and they get hit by a car, etc.
It might not be that full trauma of being hit by a car. It could just be they ran down the bank, broke their leg, etc. But it's all the other things that potentially come with it.
Once that bone's broken, pain, they haven't been eating very well, and maybe there is a stress response there and we can now oscultate some, catecholamine release and arrhythmia that has been presented. So I thought this was quite interesting. Just our, what we might assume to be a healthy animal with a simple fracture, actually, the study found that these guys were high risk.
This particular study, They said that pre-anesthetic radiographs may provide important information to assess ASA grading in traumatised patients and therefore influence the anaesthesia protocol. So that's just adding that further diagnostic onto our patients' anaesthetic examination. And this study here that came out of JSAP, they found that anaesthesia and analgesia agents were changed in 23% of cases after a clinical exam, but only 8% of patients had their ASA grade reclassified.
So what they found here was that generally in this particular study, drugs were changed, but not necessarily the grade, so the risk didn't go up in that patient's anaesthetic, but interestingly, clinicians chose to perhaps change drug doses and protocols and drug types instead with the with the idea that maybe they were going to anticipate something happening to that patient going forward in the procedure. Another group of studies here, and this was a study that was done between vets and also students at a hospital in Brazil. And despite almost all veterinary students and veterinary surgeons being taught gradings, when they were presented with 5 clinical cases, they were classified in at least 3 different types of classification between the groups, showing that there is weak inter observer.
Agreement. So what we can see here is that a lot of times ASA grading can be subjective. So it should really be holistic when we talk about our patients' anaesthetic risk.
One person may grade that patient as an ASA 2, and another may be grading that patient as an ASA 3. And it isn't a cause to understand why you're fighting and disagreeing. It should be like, oh, OK, what, what have you seen that I haven't seen?
So we've got to understand that ASA grading is subjective, but it is a really good way to open a line of communication as to something someone may have missed or maybe they've got experience with that particular comorbidity in the past, and they really don't think, judging on that patient's clinical presentation, that it's going to be a risk factor in their anaesthesia. This, study here, this was a study where an ASA grade was assigned to a particular patient. And then they, they did further testing on that patient and then reassigned them an ASA grade.
So what they did find was, yes, some animals did shift ASA grades, but ultimately no patient shifted by more than 2 classes. That was their outcome. No patient shifted by more than 2 classes, which kind of implies, right, you're not going to go from an ASA 1 to an ASA 5.
Sure, I understand that, but you absolutely could go from an ASA 2 to an ASA 4. So a somehow mildly affected patient that just has a little bit of clinical disease, a little bit of systemic dysfunction going on, and then after some further diagnostics had been done. How they got bumped up 2 extra grades and they got put into a high risk category, I think that's quite staggering.
The statement saying no patient shifted by more than 2 classes. I'm thinking it shifted 2 classes. I can understand going up or down 1 or 2, sorry, going up or down 1, but going 2 is, is that caught me off guard when I read that.
And then this last study as well that did come out of the JSAP, and this was one that was specifically focusing around mitral valve disease in patients and assigning ASA grades to them. And I thought this one was really interesting. It's, it's hot off the press.
It literally came out in March this year, so it's only a couple of weeks old. So what they found was that mitral valve disease is the most common canine heart disease. An ASA scoring alone poorly reflected anaesthetic risk due to the variable disease severity.
So this was quite interesting because further back we discussed, yes, ASA grading can give you an indication on patient risk and health status, but also our physical examination alongside of that can determine how well or how much reserve that patient has of the organ systems that are affected. So I thought this one was super targeted, really nice to read, because yes, a patient with a mitral valve disease does go up in the risk category. But they might go up further if they are, really suffering from quite a significant, severity of their mitral valve disease.
So they propose in this particular study that we do not just a physical examination, radiographs, but also things like proBNP and pocuses as well. So, in summary, the ASA status is a useful tool to predict risk with higher grades clearly associated with with with worse with worse outcomes, sorry. But, however, it's really important to remember that grading is subjective.
It will and can vary between clinicians. A thorough history as well is more important. These animals are going to be guided by the anaesthetic plan with what's in front of us, and when we grade them, we can then flip through one of our textbooks and kind of double check ourselves that perhaps the drugs that we are choosing are satisfactory and suitable for that patient.
And ASA is best used as a communication tool, both within the clinical team and also when discussing risk with the owners. So, overall, it supports decision-making, but it does not provide, or replace anything extra to, a normal amount of clinical judgement. What do our guidelines say about doing further, diagnostic testing on top of ASA gradings?
We have got our standards of care, that have come out here from the anaesthesia guidelines for dogs and cats out of Australia. And they have said that there's no evidence to indicate the minimum time timeframe to perform laboratory tests and examinations in our patients, so we can't say, oh, we tested that patient last week, or we examined that patient patient last week. We fundamentally should be reassessing them on the day of surgery as well.
And then when we have a look at our 2020 AHA guidelines, and they say that individual patient diagnostics can include this minimum database that we've talked about and other components as well. And then our AVA guidelines that, they state that an anaesthesia plan should be considered for each individual patient. So, interestingly, when, when we put all of this together, We can see that we can add in blood tests, we can add in further diagnostics to complement our patients' anaesthetic plan, but we can't say things will be safe because we tested them a week ago or a month ago.
It really does depend on that patient that's in front of us. And lastly, before we go through other factors that can increase patient morbidity mortality, when we are trying to make an aesthetic plan for our patient and to, Assess them pre-clinically, pre-anesthesia is, these really interesting guidelines came out in 2023, once again from AA, and they are the senior care guidelines for dogs and cats because as we move on, you will see that age. Is somewhat of a factor in our pre-GA clinical assessment.
So, I'm not going to go through this, through this one, but it does tell us for our senior animals, it gives us guidelines on how frequently we should have things tested, and this will typically be routinely, and you may need to repeat them as well if they're coming in for a procedure. Procedure urgency is another key factor in influencing risk. So we generally divide cases into 3 different types, scheduled, urgent, and emergent.
So, as urgency increases, so does risk, largely because we have less time to stabilise that patient. In dogs, emergency procedures are associated with around 2.5 times an increase in mortality.
With major surgery, obviously further increasing that risk. And we see the same kind of trend in cats too. So wherever possible, stabilisation before anaesthesia is critical, but in true emergencies, we often just have to accept.
Higher risks. We have to get them as stable as possible, but sometimes trying to take too long to stabilise them can actually put them in further trouble. So think about that bleeding spleen patient as well.
We know we need to get the spleen out. It is bleeding, but we do have to stabilise them as much as possible. So we just have to accept that there will be higher risks.
Also in regards to procedural urgency, it will also depend as well on how stress-free that patient is. So, of course, we're going to get animals come in that we may not have booked in for that day, they have arrived off the streets, whether they've cut their paw pad while out walking or they've been hit by a car and sustained a massive traumatic event. Procedural urgency also means we skip, typically we skip that stress-free handling and approach to anaesthesia.
If we also do have a stressful patient that's presented in front of us, even if it is for something routine and we can't examine them. Then we tend to drug that patient for the protocol and for the, sorry, we did, we tend to make drug protocols for that patient's attitude and not necessarily their health status. So if possible, can we go back and reschedule that patient after we have given them maybe some drugs that we can, that can be administered at home to, to calm them down, to chill them out.
And we do have our chill protocol. So chill, we've got the C, meaning calm patient. Make them handable, lightly immobilise them, allow for low stress when we handle them, and lower that sympathetic tone.
So when we think about procedural urgency, it isn't just how emergent that procedure is in front of us. It's also assessing can we make this patient's procedure. Less stressful, with less of a catecholamine surge, with less fight or flight or fright going through them, and allow us to really handle that animal, examine them properly, maybe do some further database testing or diagnostic testing.
We should also factor that in as well to procedural urgency. Can we postpone by just a day if possible, so that that client can go home, medicate their pet there, and then we try again. Looking specifically at age when we are doing a clinical exam on our patient and maybe even some further blood testing, age is another important factor, particularly when we're at the extreme of patient ages.
So, In dogs over 12 years old, anaesthetic risk increases significantly up to almost 10 times. While in cats, it's around a 2-fold increase. Now, is this just because we see less cats coming through for older procedures?
Potentially. I think now, thankfully, we are getting cats living quite long and we're shifting that mentality that these cats are outside mice catching. You know, barn animals, they are our indoor health, you know, our indoor, happy, healthy pets.
So if we do get our older animals coming in, in the next few years when we start to do another data capture, maybe we will see this risk increase, but I do wonder if initially, coming out of the SEPSAF study 20 or so years ago, we treated our cats differently and potentially didn't necessarily put them under anaesthetic because we had a different way of thinking as pet owners there. So, Why is there such an increase in different extremes in patient age in regards to morbidity morbidity, mortality and the risks of anaesthesia, so. Age itself isn't the problem, it's the associated comorbidities.
So older patients are more likely to have underlying diseases, which will increase their ASA status and therefore overall risk. The key is not to treat age alone, but to identify and manage the conditions that come with it. Obesity, this is also an important and often underestimated risk factor when we are doing a clinical assessment of our patient and booking them in for a procedure.
What we can see in cats is that in cats that are over 6 kilogrammes, anestitic risk can be up to 3 times higher than a cat that is between 2 to 6 kilogrammes. It's even greater, of course, than in our higher ASA patients. So a key issue around obese patients is that we have altered pharmacokinetics.
So this will be drug distribution, metabolism, the clearance of the drug. These will all be affected. Therefore, dosing of preanesthetic drugs should be based on lean body weight.
So you will find you have to use lower doses. We do not need to dose them for their obese weight. It should be an appropriate lean body weight for that breed and if they are male or female.
Additionally, obese patients tend to also have slower recoveries. Once again, that distributed, that distribution of drug is affected, but potentially there is that subjective overdose as well, playing a factor when they were dosed for their obese body weight. On top of that, our obese patients will also have this reduced respiratory function.
And a decrease in cardiovascular reserve. So overall, these patients, while cute, I do like a chunky patient, they do have a higher risk. We need to be really careful when we dose these patients whilst we are monitoring them and also how we can plan to recover them.
Looking back as well on that SEPsA study, when we have a look at morbidity mortality. Most, if not like all about 47% of cats and over 50%, over 50% of dogs, sorry, no, 40%, 47% of dogs and over 50% of cats, they actually die in the recovery period. That's the most dangerous high risk period for a patient undergoing anaesthesia, and they do it within, within the 1st 3 hours.
So an obese patient that will have the slower recovery, automatically, I'm worried about how they're going to recover, especially when I know that that is already a high risk period. Interestingly, very small patients also carry an increased anaesthetic risk. In cats that are less than 2 kg, this risk is dramatically higher.
So it isn't just younger patients, it's also smaller patients. But focusing on younger patients, this is largely the complication around this is largely due to paediatric physiology. So these patients are more prone to hypotherm.
Ther m ia to hypoglycemia, and they also have immature drug metabolism pathways. So, drug dosing needs to be extremely precise. Small errors can lead to quite significant overdose in these patients.
So, tools such as, using insulin syringes and weighing the patient on a, a little kitchen scales so that we can understand right down to the ground that that patient weighs is really beneficial. IV access in these smaller guys is also a little bit more difficult. So is airway management.
It can be quite challenging in our smaller patients. So overall, these patients require careful handling, accurate dosing, and extremely close monitoring throughout, especially once again in recovery. When we have a look at our canine data, it shows us that dogs under 5 kgs, they also have quite a significant increase in morbidity and mortality, because of their size.
I mean, the difference between cats that are less than 2 kg and dogs less than 5 is quite drastic, but, still very interesting and something to keep front of mind for our patients too. What about pre, pre-GA blood testing? So, initially when we started this talk, we did mention all of the different tests that we can do that will complement a physical exam when warranted.
We know in human medicine that it ends up being quite costly to just do tests on every single person that goes through for an anaesthesia. So we have to target it. And there There are so many papers on it.
This slide summarise, summarises the evidence around pre-anesthetic testing in healthy patients, in unwell patients, in those coming for a GA and those that are just having, a wellness clinic checkup if it's part of your pet care plan. The studies that are listed here also try and differentiate between whether an anaesthetist ties to, predict. The findings of a blood test based on the patient's clinical exam, which I thought was quite interesting.
If we have an animal that comes in that is older, they look clinically dehydrated, the anaesthetists were able to predict that the lab results would therefore show that, and then they could, they could change that anaesthetic plan just on their predictions versus actually doing tests. I wouldn't say this throws out the idea of doing pre-GA blood testing, but, but perhaps for that cost-conscious client, we can instead use our physical exam and, ASA gradings to kind of predict any changes that we have to, have to make. So overall abnormalities, they were quite common, especially in older animals.
That won't be a surprise, but they don't always change the anaesthetic management. In many cases, The testing reflects which patients were already at a higher risk just from their clinical exam, just from understanding the previously diagnosed comorbidities, rather than the, the testing being the cause of changing the anaesthetic plan, it's that, the testing just kind of confirmed that that patient was already going to be at that higher risk. What's important is that while routine testing may have a relatively low impact on ASA grading and classification, All protocols in healthy patients, it can still identify in some patients subclinical disease, particularly in older cats and dogs that are assumed healthy based on their clinical exam.
We can start to see maybe some of those organ systems declining. And we know that with cats now, we know that we don't have to wait for high urea creatinine. Readings, we can instead do other kidney biomarkers and get a better understanding of their kidney function before big red flags are waved in the blood protocols.
So, the key message is testing has its value, but it definitely should be targeted and interpreted alongside this clinical examination and the patient history that's been gained from the client. So ultimately, Aside from all of the things we can add to our pre-clinical assessment, clinical assessment itself from that physical examination remains the most important factor because it's often we're able to predict what we might find with the blood results and change our plan accordingly without taking those bloods if there is a reason to not cost conscious clients, for example. So, in conclusion, the clinical exam, the patient history is the most important to change ASA grading and protocol.
There is a potential to find some clinical disease. But it's useful to know that sometimes when animals come in for a GA when that dental disease is really bad and the owners are finally fed up with the smell, for example, this might be the only time a blood sample is going to be taken in that patient. So yes, let us take some blood, because it might be the first time in 5 years that a patient's having a blood sample, and it might be the last time for the next 5 years that patient's going to get a blood sample.
So let's, let's get something done. Wrapping it all up together, a nice stepwise approach to the pre-general anaesthesia assessment would be starting with history taking with the owner, then a physical exam. Going on to identify different modifiers to that patient's anaesthetic plan with the big ones being age, obesity, urgency.
From there, we can decide if we need to do further diagnostics. Then we can assign that ASA grade after we have a full clinical picture inside and outside of that patient. And then from there, we can use chapter 13 from the BSAVA book to guide our protocol if we need to change anything, add anything in, doses, etc.
So in summary, pre-anesthetic assessment is more than just ASA grading. History and exam taking is the most important tool. Running routine bloods does have, it appears, limited value in healthy patients, but it is useful in older patients or those at a higher risk.
Even if they don't clinically look sick in front of you, it can, bring to light some underlying diseases. And let's consider that risk can increase with age, this rise in ASA grading and also urgency. But ultimately and fundamentally, when we do our pre-GA assessments, we've got to individualise the patient plan.
So I always think with practise protocols that are done, they are not patient-specific protocols. They're protocols for the practise because it's easy to do. Everyone gets really familiar with those drugs and there's a standardised approach, but our patients are not standardised.
Between breed, age, comorbidities, or the procedure that they're undergoing, that's not standardised. Let's start treating our patients a little bit more, individualised. Hopefully you feel a little bit more confident now around different types and ways you can perform a preoperative assessment.
The advantage and the understanding of what we can gain when we do further diagnostics, and also how we can wrap up all of that information together to support our clients and to guide expectations and outcomes for them and their patient too.
