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Hi, good evening everyone. Can you hear me? Yeah, that's loud and clear. We'll just give it maybe a second or two for to let uh people join in and then we can crack on. So perfect. Uh Lean has given us the thumbs up. Uh uh carry on. Uh So lovely. Ok, so, good evening everyone. Um, like she has mentioned, my name is, I'm one of the CT two anesthetic trainees based in the northeast and I'm gonna be talking about physiology and peroperative management. I might take myself off video if that's OK for the presentation, but I'm still here, feel free to ask any questions and we'll get back to you either during the presentation or right at the end. Ok. Right. So these are the learning objectives that we're gonna be trying to cover. Now, there's quite a lot that was listed. So you might not be going into great detail, but we'll give, give you a good overview of what it is and then we can discuss any questions in depth about um particular surgeries and I'll do my best. Um First of all, we're gonna be looking at Perioperative Management. So, understanding why it's important the significance and surgical care for yourselves as surgical trainees in terms of planning your cases preoperatively, the principles of the assessment optimization of patient comorbidities and risk stratification, which is really important in terms of determining outcomes. Then we're gonna be looking at concepts in physiology, um mainly with the main organ systems of cardiovascular respiratory and renal physiology and how that's relevant to surgical practice in terms of the acute stress response, the homeostatic mechanisms that we essentially disturb by administering anesthesia and surgery. And finally, we're gonna look at how we modify this intraoperatively and perioperatively with decision making based on the principles that we've discussed. Ok, so we'll just crack on. So actually thinking about preoperative medicine, it's a pretty complex multidisciplinary specialty and it's been driven by more complex surgical populations, which basically means that patients that wouldn't be having surgery 1520 years ago are now being listed for theater for elective surgery. And it's based on advancing anesthetic and surgical techniques which we know are available to us. So it's not exclusive to one speciality. It is led by anesthetist, but it's very much a collaborative effort between anesthesia and surgery um to undertake the role of the perioperative physician. So risk assessing of the surgical patient um can be divided into a couple of things, primarily, of course, the medical and surgical history of the patient itself. So prior comorbidities and um concurrent medical conditions that will need to be managed both before and after the surgery itself. C pap or cardiopulmonary exercise testing has become a really big thing of late. It's basically a marker of the coupling of external to internal mitochondrial respiration. Ok. And it provides an individualized assessment of cardio respiratory function and fitness. And we normally do this by popping the patients on a bike or a treadmill. And um, but obviously, these can be tolerated less well by patients with musculoskeletal issues or those who going in for joint replacements and so on, that can pose a greater risk for falls. But if they can tolerate CPAP, um there are basically four key physiological stages. There's the cardiodynamic, increased cellular respiration, ok. There's the steady state and then there's the incremental work phase as we kind of make it harder and harder for them to be on the bike and so on. So in terms of actually determining outcomes, um perioperatively, we know that anaerobic threshold, peak oxygen consumption, which is your peak V two and your ventilatory equivalent. So that's your be by D EC2 V. They've been specifically shown to be independent predictors of mortality and morbidity as well as length of hospital stay. Ok. And these are all kind of markers that you can get off putting someone through cardiopulmonary exercise testing. So once you kind of identify risk, it allows for prehabilitation of patients, there'll be a slide in a bit, that kind of shows you where all of this sits in terms of the surgical pathway. But prehabilitation allows for um lifestyle modifications, you know, common things that you'd expect in terms of smoking cessation, um alcohol reduction, better nutrition, especially for those who potentially are malnourished at high risk of um poor wound healing. Psychological support for those who have anxiety who potentially aren't going to comply with postoperative instructions and um exercise programs as well. OK. We'll talk a bit more about the stratification tools in a bit. So I won't um go on about that too much. OK. So in terms of optimization of, of medical conditions, you know, diabetic management is a big one of them. And most patients who are diabetic type one or type two should have a HBA one C that's done by their GP. I'll give you a bit of a snapshot picture of what their diabetic control is like over the last three months. This also is an opportunity to kind of discuss what things, what's gonna be done intraoperatively in terms of insulin management, whether the patient needs to go on a sliding scale and postoperatively how quickly they're gonna go back to the regular insulin regimes and whether any adjustments need to be done, there's a lot of work recently done on the management of anemia. Um sort of low HB S those who are iron deficient and so on. And it's been shown that patients who are anemic benefit from iron transfusions or blood depending on how urgent the operation in question is um cardiovascular risks. And this can be divided again into a couple of different comorbidities. Patients with hypertension, um whether it's uncontrolled or controlled hypertension need to be reviewed in terms of what we're going to do with their medication. And if it's uncontrolled, whether we can afford to wait um for, you know, a better target by referring them back to their GPS. Um patients with ischemic heart disease, uh obviously at increased risk of type two mis postoperatively even when managed appropriately. So that's something that needs to be discussed, potentially referring back to cardiology for further investigations, including angiograms, um patients with stents and what we're going to do with um their medication preoperatively as well. Aspirin, clopidogrel, and ticagrelor and so on. And that leads on nicely to the planning of anticoagulation for other reasons as well. Ok. Vascular paths, patients with P ES and DVTs, these are all things that need to be considered in preoperative assessment. And then once the patient is listed for surgery, it allows for forward planning of admission. Ok. Whether the patient is gonna end up coming back to the ward, whether they pro potentially gonna need pacu. Um so a high dependency bed or potentially an ITU bed. Ok. So this is a slide just to show roughly kind of what the timeline is like or what it's supposed to be like for those who are um coming into preassessment clinic and as you can see, it actually starts from a GP referral. OK. And it goes on to diagnostic test, tumor staging. So on an MDT discussion and a surgical clinic, if you look a bit lower down, there's also mention of a surgery school. And essentially, that's a, a concept introduced by nice where it's a multidisciplinary picture where you have surgical anesthetic and um rehabilitation input, which allows the patient to be optimized prior to surgery. Now, all of this obviously is with the caveat that you're looking at an elective procedure and you have time, which is the the main sort of factor in terms of planning um perioperative modifications, patients that need to be listed for surgery within two weeks, you have a much smaller frame to actually make adjustments. Um and those that can wait a couple of months obviously are gonna benefit from more interventions in terms of perioperative management. So risk stratification tools. So there are many available scores and models and it's not established which score is the best predictor of risk. So you can imagine it's quite a complex question and each comes within their own limitations and it needs to be taken into relevance to the specific patient and the required input variables. So a really common scoring system, the P possum scores, I'm sure most of you have heard of. It's a two part scoring system. It includes a physiological assessment and a measure of the operative severity. So the physiological part of the score includes 12 variables. It's divided into four grades and you've got an exponentially increasing score and the physiological variables are those that are really apparent at the time of surgery. Ok. And these include clinical symptoms and signs and it's the results of simple tests. Um, blood tests, biochemical and hematological investigations and ECG changes. If a particular variable is not available, you allocate a score of one and some variables may be assessed by means of just clinical symptoms or signs. Um The minimum score therefore is 12. Ok. With a maximum score of 8 to 8. The operative severity part of the score includes six variables and the number of operations indicates the chronology of the procedures within 30 days. For example, an example of surgical magnitude of general surgery um can be also demonstrated. And then once these scores are known, it's basically possible to estimate the predicted risk for mortality and morbidity. So the sort score is a surgical preoperative risk prediction tool. It also provides a percentage estimate of death within 30 days of inpatient surgery for adults. Um and the exclusions in the first version of sort including obstetrics, neurosurgery, cardiac and transplant surgery. Ok. And it has an advantage over many existing prediction tools by consisting of solely preoperative variables and allowing pretty easy data entry. And it's just another scoring system that you could also easily find online. And finally, you've got the A CSN S quip surgical risk calculator by the um American College of Surgeons. And it estimates the chance of an unfavorable outcome such as complication of death after surgery. And it, the estimates are calculated using data from a large number of patients who've had a surgical procedure similar to the patient that you're proposing. So essentially when you enter in your data, you're going to be asked questions um regarding sort of basic cardiovascular and respiratory fitness, sort of things like COPD hypertension, um diabetes, as well as the particular operation that the patient is having. And it compares the outcomes from similar patients of, of a dem patients of a similar demographic um who've had that procedure before. Ok. So the next slide is basically grading tools um that are really common surgical grading tools that are used both from an anesthetic and a surgical perspective. So the A SA grade essentially looks at the systemic um disease of the patient. A SA grade one being a normal healthy patient without any clinical comorbidity as you'd expect. These are pretty rare and probably these sort of simple day cases patients that come in for minor operations like ent procedures and so on. With AC grade six being actually a new addition to the to the system that's in brain dead patient whose organs are being um harvested for donor purposes. As you'd expect most patients kind of sit between two and three. and N has actually recently reviewed the A creating to include those who smoke to sit um, at an A SA too. And they've modified some of the guidelines in terms of high BMI S. So I'd encourage you to have a, a look to see where patients kind of sit on that system. There's also the adjunct of E, so you can get a, um, grade one E, two E and so on. And that basically means the patient is listed for emergency surgery. The nice surgery grade on um the other side basically lists the complexity of surgery. And that is an idea in terms of not only just kind of giving you an idea of how invasive the procedure is, but what kind of complications you might expect. And it's also used, I believe in terms of um funding and sort of coding from an administrative perspective. So the last bit of sort of preoperative assessment is looking at routine preoperative tests for minor surgery. So you'd be surprised or maybe perhaps not. So that um a lot of patients can be listed for surgery without any um preassessment, bloods or preassessment investigations, which is fine if they meet this um particular criteria that is guidelines, as we've seen on the side, they're a nice guidance on um who requires what, but we don't offer a lot of routine testing in terms of sickle cell HB A1C, um or so on for those who don't have any indications for it. Um It also means that you can potentially have some surprises interoperatively. You all patients will be recon saved and so on. But it's just something to consider at preassessment whether or not these patients are gonna have these investigations and what you would do if you were to run into trouble with it. So right next, we're gonna be looking at the physiology of the surgical stress response. Ok? And that's essentially what happens every time someone does have surgery. It is, um, a stress response is from the body that you would get with trauma. Essentially, it's difficult to differentiate the two. And we're gonna break this down into three parts. Um, the first being sympathetic nervous system activation. Ok, which is the sym sympathoadrenal response. You get hypothalmic activation of the sympathetic autonomic nervous system. And this is what sort of increases your secretion of catecholamines from adrenal Magela. And it's a release of Norine from the presynaptic nerve terminals, which is primarily primarily a neurotransmitter. But there's some spillover which release is into the circulation. And this is kind of what causes the well recognized cardiovascular effects of surgery, tachycardia hypertension, and essentially the pain response that you get from a patient in case they're not adequately energized or anesthetized. In addition, the function of certain organs like the liver, the pancreas and the kidney. It's modified directly by efferent sympathetic stimulation and or circulating catecholamines. The second bit. Um from the surgical stress response is the endocrine response with pituitary hormone secretion and expected insulin resistance. And if we look at the hypothalamic pituitary adrenal axis in a bit more detail. Um the anterior pitu hormone secretion is stimulated by hypothalamic releasing factors. Ok. So the pitu synthesize is called trophin or ACTH as part of a larger precursor molecule. The precursor is metabolized within the pituitary and ACTH. Um beta endorphin and the internal precursor and the growth hormone and prolactin are also increased in um amounts from the pit in response to surgical stimulus. So you get an increase in ACTH growth hormone and prolactin concentrations of other Teri hormones aren't really affected. To be honest with the, the TSH, FSH and so on. They don't really change markedly during surgery. So we've h in a little bit on a, it's a large amino acid peptide and it's producing the pituitary from the larger molecule as we talked about and ach stimulates the adrenal cortical secretion of glucocorticoids so that the circulating concentrations of cortisol are increased. Now, surgery is one of the most potent activators of ACTH and cortisol secretion. It increased in the plasma concentration within minutes of the start of surgery. Cortisol secretion from the adrenal cortex increases rapidly following the start of surgery. And it reaches from baseline values of about 400 nanomoles A liter, right up to over 1500 nanomoles a liter, ok, within 4 to 6 hours at the start of surgery. And depending obviously on the severity of the surgical trauma. Now, this response can be modified by anesthetic intervention. But when we modify it, we're kind of looking more at sort of the end effect of cortisol rather than the actual endogenous secretion. So you still do have a baseline stress response at all times. Cortisol in itself has complex metabolic effects on carbohydrates fats proteins. And it promotes protein breakdown and glucogenesis in the liver. So the glucose of u the glucose used by cells is inhibited and blood glucose concentrations are increased as you'd expect with the stress response, it promotes lipolysis, which increases the production of um the breakdown of triglyceride into cholesterol and fatty acid. There's also a huge effect of cortisol on um anti-inflammatory activities. So, corticosteroids inhibit the accumulation of macrophages and neutrophils into areas of inflammation and they can interfere with the synthesis of inflammatory mediators, particularly prostaglandins. So, the net effect of the endocrine response to surgery is an increased secretion of catabolic hormones. And this promotes the provision of food fluctuates from the catabolism of carbohydrate fat and protein. And it seems less likely that the stress response developed as a survival mechanism which kind of allowed people to sustain themselves until their injuries were healed. And by using stored body fields and sort of retaining salt and water, it kind of gave you a better chance of healing and repair. Obviously, in current surgical and anesthetic practice, it's questionable about whether or not this is actually necessary. So finally looking at the third section, um the immuno immunologic and hematologic changes including cytokine production and the acute phase reaction of neutrophil mucositis and ly toy lymphocyte proliferation. Sorry. So, cytokines in themselves are a group of low molecular weight proteins and they include interleukins and interferons. If you remember back to medical school, they are produced from activated leucocytes, fibroblasts and endothelial cells. And they're really early response to tissue injury. They have quite a big role in mediating immunity and inflammation and they act on surface receptors on many different target cells. The effects are produced ultimately by influencing protein synthesis within these cells. The effects of chronic stimulation of the side to kind network. Um for example, on sepsis has also been looked at. Um but it's sort of an acute phase reaction that we look at during surgery. So we've talked about the role that they have in the inflammatory response to surgery and trauma. They've also got local effects of mediating and maintaining the inflammatory response to tissue injury and there's some systemic changes that occur. So after major surgery, the main cytotype cytokines that are released are interleukin one. So it's il one tumor necrosis factor alpha T NFA and IL six. The initial reaction is the release of Il one and TNF alpha from activated macrophages and monocytes in the damaged tissues. And this stimulates the production and release of more cytokines and a sort of positive feedback mechanism. In particular Il six. The main cytokine responsible for inducing systemic change isn't known as the acute phase response. So, a number of changes occur following tissue injury, which is stimulated by cytokines, particularly il six. And one of its features is the production in the liver of acute phase proteins. So, these proteins act as an inflammatory mediator, anti anti proteinases and scavengers and in tissue repair as well. And they include um crp fibrinogen alpha, two macroglobulins and other proteinases. So, the increase in serum concentration of CRP follows the change in il six production of other proteins in the liver. For example, albumin and transin decreases during the acute phase response. Which is why a lot of patients get hypoalbumin um postoperatively or those who are chronically ill and have long, it stays require um albumin not only to increase sort of oncotic pressure, but to actually replace um the decreased synthetic ability of the liver in itself concentrations of circulating cas such as zinc and iron decrease as a consequence of changes in the production of transport proteins which the liver is also responsible for. So I'm gonna talk a little bit about um the physiological changes with anesthesia. So obviously, this depends largely on the anesthetic agents that are used. Um but they can be loosely categorized into the effects of the cardiovascular respiratory and renal systems. So, anesthesia in itself comprises of a hypnotic agent, um paralysis and analgesia and typically you'd use the drug such as propofol to induce hypnosis. You'd use opioids for analgesia, um, potentially a neuromuscular blocker if you needed to paralyze the patient for either intubation or for abdominal surgery and so on. And you'll also have an element of um, hypnosis and amnesia of those medications. Most anesthetic agents including volatile gasses and propofol will cause systemic vasodilation. And that's why you get your drop in BP. Now, this can be mitigated by other medications which are administered such as glycopyrrolate and um EDR. But you know, there's a a systemic response to that, which is why we try and maintain um perfusion with fluids and or titration of the anesthetic to make sure the patients are anesthetized sufficiently for the surgery, but not quite so much that you are requiring large boluses of these suppressors to maintain their BP. Um This comes hand in hand with having both negative inotropy and negative chronotropy in terms of the heart. Um but this is particularly relevant for those who have cardiovascular disease or might have um a block or arrhythmias that we need to be aware of. And obviously the the big sort of effect of anesthesia um is on the respiratory system in itself. Patients who've had um neuromuscular blocking agents or even those who are just under sedation, have complete loss of reflexes and muscular tone, which makes it easy to intubate anesthetize but causes everything to collapse in on itself, including the respiratory muscles, the in intercostal muscles, the diaphragm and so on, which means you get a reduced um frc reduced minute volume, reduced respiratory rate, and finally, of course reduced tidal volume, all which means that we kind of leave them vulnerable to not ventilating themselves appropriately if that's not managed, similar to the effects from the cardiovascular system. In terms of systemic vasodilation, um the renal system itself is very sensitive to the effects of anesthesia. You get hyperperfusion of the kidneys and there are a lot of microvascular changes that can happen in terms of inflammation and tubular cell injury. The tubular cell injury obviously can be an effect from the administration of the medication or the drugs that are used in anesthesia. But it can also be sort of um separate from just the medication involved, but also sort of the cytokine release and the inflammatory response that happens with surgery as the kidneys filter that through in patients um that are perhaps positioned suboptimally or in a they're not a not position for surgery, you can get backflow of blood. You can also get um a venous congestion just off the systemic vasodilation and that can put an additional stress on the kidneys. And it's not uncommon for patients to have achy postoperatively as I'm sure that you know. All right. So finally, if you look at how our knowledge of physiology in affects our physicians interoperatively, if you think about it, there are three main points or sort of main things that we need to focus on in terms of keeping a patient safe and optimizing surgical conditions um in the preoperative intraoperative and postoperative periods. The first of course, is maintenance of homeostasis and essential organ functions. And we've talked about both optimizing the patients from their preoperative conditions to make sure that um you, you come into the operating theater in the best of states and we're able to maintain that organ function throughout the operation, um and have an appropriate plan afterwards in terms of where they're going to be managed. Now, this can be done in terms of drugs. So that means BP support by using vasopressors um appropriately. So maintaining a map that's appropriate for their patient. And this can be dependent on what their baseline BP is like patients who are frail or had previous cardiovascular disease or um CVS events, we might need a map that's slightly higher and this can be titrated accordingly. Patients who are younger fitter can essentially do better without as much intervention in terms of optimizing surgical conditions. Um This largely depends on the operation. The patient is having patients with um patients who are getting um ent surgery, for example, will potentially need lower BP targets um positioned in a way that, you know, blood doesn't obscure the surgical field. Patients who are having vascular surgery might require slightly higher targets. And obviously, depending on what's happening at the point of surgery. Um This can be titrated accordingly. And then finally, sort of looking at postoperative cab and considering where patients need to be managed after they have surgery, this can depend on postoperative analgesia. So whether the patient leaves the operating theater with an epidural, they've, whether they've had a spinal anesthetic or um whether there are any nerve catheters in place, and it can also largely be dependent on the hospital that you're working at as well and what your nursing staff are comfortable with in terms of recovery or in terms of managing patients um on the ward and what they're, what they're happy being sent out with patients who have been unsta have been unstable during surgery, potentially might not be extubated and will need to be transferred as a level three to itu. Those who just require a couple of hours maybe uh to be weaned off by suppressors such as Metram, you put the arterial line in situ and so on can be managed quite happily in a HD or a pacu bed before they stepped down to the ward. And just by thinking about um the baseline physiology of the patient, what they've been like in theater and as well as the kind of targets that you're aiming for postoperatively. So, depending on the surgery that they've had, you can think about whether they would be more suitably managed, right? So that was a really quick whistle, whistle stops, trial through perioperative management. Um and some of the overly headings of what the surgical response to physiology is, what the physiological response to surgery is like as well as um to anesthesia. Happy to answer any quick questions. All right. Thank you for your time, everybody. Um I'm happy to forward on any papers and resources that might be useful to you based on the topic. Thank you so much for that. Um, doctors in that frame, I think with anesthetics and physiology, we tend to sort of find it a bit difficult, especially from, from an mcs standpoint because of the fact that there's not much resources that we can sort of come across. So hopefully this will give you a good insight into, you know, what you need to focus on and how best to sort of, you know, manage different situations and different stations, especially for Part B. So if there's any questions, please drop a comment. Um I think what we'll do is we'll definitely put these slides up onto me all. Uh most importantly, please, uh sort of, you know, um send across feedback forms so that we can sort of assess exactly what you all thought went well, what we can improve on and again, please join us for our next session uh this Thursday at 7 p.m. as well. And I'll drop a link on the message chat just so, you know, we keep this going and hopefully your exam prep for part A and Part B is coming. Uh is, you know, coming along quite well. So thank you so much for that Doctor Sander. And again, we'll stick around if there's any further questions.