Thank you very much, Bruce, and thank you very much for everybody that joined. I sincerely hope there won't be any more Kremlins, so that we can continue with this talk. So in essence, my main passion is to install enthusiasm for anaesthesia and pain management.
And I often find that students and nurses and often our surgical colleagues think that anesthesiology is exceptionally boring. But just after this glitch, that's typically how anaesthetic works. You've got these hours and hours of boredom and then this interspersed with these few moments of sheer terror.
So, what I'm trying to aim at is not discussing the monitoring as you normally would do it, is how it works, what you would normally see, but to try and ascertain what can go wrong, what is interpreted wrong, so that we can go back to the boring part of anaesthetic and just watch it as everything goes by. So in essence, welcome back to the flood deck. So often we've been told that anesthesiology is very closely related to aviation.
In a mere sense that we sit with a multi-parameter monitors these days. You have to make split-second decisions, and you have to make sure that what you are interpreting and what you are ignoring is actual fact. I'm not going to give away my age, but in essence, when I qualified, anesthesiology was easy.
You just see if the patient was breathing. If he was breathing a bit faster, you gave him a bit more isofuran and that's where you stop. But for us these days, multi parameter monitors is becoming increasingly sophisticated, becomes more available in private practise, and it becomes really crucial for safe anaesthetics.
But it still can't replace an attentive anesthesiologist. We don't have those robots yet. Luckily, otherwise, we don't have jobs.
But the important part for me is that the information that's so diligently written down by the nurses or by the residents or by whomever is monitoring the case needs to be interpreted. And based on that interpretation, we can take some actions. There's no use of writing a whole anaesthetic sheet.
It looks absolutely perfect, but nobody actually looked. At the values of what we've seen. Now I think the previous speaker's point is really valid.
It's exceptionally important to know what your patient looked like before the anaesthetic, before you continue. The second point to me that's really of paramount importance is treat the patient, not the monitor. If anything goes wrong, check your patient first because you start, before you start troubleshooting your monitors.
Monitors are prone to failure, and if we do understand how monitors get the numbers or the graphs to display, we can recognise the common errors made by these monitors and then we can troubleshoot them. So often we tend to ignore annoying alarms, especially if it goes off repeatedly. You just blank it out, you don't look at it.
Or the alternative is you might react to alarm, which is actually not telling you the truth, and both sides of that coin can land you in trouble. And yes, what we are looking, so I'm only going to discuss cnography, pulse oximetry, and blood pressure just of time. And what we are interested in is what's happening on cellular level.
So we want to know. Oxygen that's produced, CO2 that's removed, but also the reverse is opposite is true. We want to know what a cardiovascular function is and respiratory function is so that we know what is happening on cellular level.
So once again, you have to look at those sides. So, hapnography provides for us a mean to assess alveolar ventilation in real time. And that's the biggest advantage we've got from all the monitors.
It also gives us information of the integrity of the airway, the function of the breathing circuit, and patient pulmonary function. Although I'm not going to discuss what you would normally see on Cabinet graphs because I want to get to pitfalls, we need to understand the basic graph. So we've got a baseline graph, which should always be at zero.
We should have a, a upstroke of the slant, which is a mixture of debt and space and alveola gate. That little angle, which is a beta angle over there, or alpha angle represents normally. I changed to alveolar gas.
If we reach a plateau, which will give alveolar gas concentration, and the E point is where the actual CO2 is measured. So if that point is all over the show, you are going to get readings that's all over the show. And then as soon as the patient inhales, that immediately should go down to 0, to the point that we get to the original graph.
So if we know what the basic graph looks like, it will become easier to ascertain what can go wrong. We find various methods of doing gapnography in small animals, and some people will just use a needle directly in June. The ET tube with various connections or they will add philtres to them, or, and all of them has got advantages and disadvantages which we need to take.
So kenography mainly It's what's available to us as mainstream and side stream ventilators. If we look at not ventilators, canographs. If we look at cano graphs, the sensor is placed directly into the circuit.
And the measurement is made directly at the patient's airway. So the advantage of that is that the sensor cannot be contaminated by any of the patient's secretions. You get very fast response time and you've got no water traps or tubing that's needed.
So that's hassle-free. The biggest disadvantage is that the original equipment that we had available to us were very heavy. They were a lot of weight.
They were bulky, and in a very small ports, it can become a problem that is and it can be damaged easily. The newer products on the market have smaller sensors, so that avoids basically that problem for us. What happens with side stream Kano graphs is that the sensor is located away from the airway, and the sensor can be contaminated by patients.
You've got a little tubing that has to Inhale absorb some of the air to be transported to where it's actually measured. This measurement is made by the pump inside the monitor. And so the slower the response time is slower than what you will have with mainstream, and water and any other secretions can be trapped in this sampling line, which can become a great problem later on.
The biggest advantages of sidestream is that it's small, it's lightweight, but small sensing tes, especially for small patients that really helps a lot. You have to have quite a length of tubing, which you have to take note of that you don't use metres and metres of tubing. And very importantly, make sure that nobody, especially the surgeon, don't stand on your tubing, or invariably, if you share an airway with the surgeon, that you don't have inadvertent thinking of these tubings.
The side stream monitors warms up very quickly, so we've got much quicker ETCO2 results and they're very amenable to remo locations like MRI because you don't have any metal parts in them. And the other big advantage is that you can use it to intubated and non-intubated patients. But your disadvantage is that you can have obstruction due to respiratory moisture, especially in prolonged procedures.
It can be blood, it can be secretions. So always keep an eye on what is happening and that little thin piece of tubing as well while you do monitoring. But where the sample size required using mainstream technologies can sometimes use up to 50 to 150 mL per minute of exhaled gas.
You have to adjust your oxygen flow to be able to mandate that, otherwise your patient's going to be disadvantaged. And it might be a particular importance when you use low flow gas anaesthesia. Also remember that you've got a bit of a response delay, 2 to 3 seconds, and periodic calibration required, and most of the machines will give you a warning that this is zeroing, do not worry about the flat line you're currently seeing on the screen.
Something that's quite often we don't take note of is where do we actually place these monitors. If you place the monitor lower than the patient, your chances of inhaling or in training more moisture or secretions that actually cause a blockage is actually quite Large. And that's why you'll have a normal graph and then suddenly it will show occlusion.
It is just because of the fact that the way you placed your monitor. If your monitor is placed higher than your patient, quite often you do not get into that sort of trouble. So what about dilution?
Our main concern is our smaller animals, our non-re with the anaesthetic circuits like two pieces or bones circuits, and we can have a dilutional artefact, and we can get false low readings. And this is mainly due to the rates of high fresh gas flows to the ratio of volume. And this dilution is thought to show artefact and to actually measure a lower ETCO2 than what is actually happening in the patient.
So the way to overcome that is to try and reduce your fresh cash flow rate to the lowest rate possible without the patients showing rebreathing. So if you monitor your patient on the Capitol, you should be able to see that there's inhalation of your CO2, which always should be reading 0. So in order to give the most accurate reading, try and go as low as possible.
And if you do do this on these circuits, we would normally use volumes bigger than your title volume. Remember, if the patient's minute volume increase or changes, you will have to change your first case in association to prevent rebreathing of that case. You have to constantly monitor that.
Often we find that peak CO2 is much lower than actually the ET CO2, and once again this is with our Macelson D and band circuits, and it's because of this dilution of gas that we've just talked about. And in essence, it's because we do not have any inspiratory expert valves in these circuits, and we normally use much higher tidal volumes or minute volumes than what the patient actually require. So the closer we can get to the sampling site, the fresh gas inlet, the more dilute the sample will be and the less accurate your of the the values will be.
So you try and get your samples as close as possible to your patient. So no very small patients and no rabbits and all of those funny things that you don't actually want to add dead space. It sometimes help to use a needle directly into the EU tube, but being careful that you don't stick the needle right through the ED tube in the opposite end because that's not going to give you any values.
And also not to the extent that you might obstruct very small ED tubes. We normally rely on a patient on a ventilator. If you look at your normal cabinet graph.
Graphs, you normally rely on the patient, exhaling, have a plateau inhaling, and to get that no square. If a patient is spontaneously ventilating, we quite often do not see that. And you can have this what we call a prolonged expiratory pause.
And the residual CO2 is still absorbed around the chamber and it continues to be sampled. And over the time, obviously that CO2 concentration will be diluted by fresh gas, but your patient hasn't taken a second breath. So you've got this very long Outdrawncani graph tracing.
And the Capni graph actually fails to recognise that the second breath has been taken because you don't have that sudden decrease to zero. And therefore, it will not register your CO2 or your respiratory rate. So a way to overcome this is to just gently breathe for the patient manually once or twice, and your curve will go back to normal and you'll be able to see your normal CO2 levels.
So what about system leaks and disconnections? And that's one of the major things that you have to look out for, especially in those small soft teas that we mentioned. Sometimes it's really just a small little crack and you don't even realise that you've actually got a complete disconnection of your little tea to your Kanegraph line.
And it's your leaks most often is around in the trifle tubes, the captigraph connector, the sample lines in the midstream models, or slow deflating ET tube curve. And so what we see is a sudden loss of the sharp definition of your capnographic trace. And this can mimic a trace of animals with impending cardiac arrest.
So at this stage, please don't resus this potion. Once again, if you just manually Breathe for him once or twice, you will see your normal capri graft tracing coming back, inflating your cuff, check for the leaks, and you'll have your normal tracing. As I said, once again, if something like this happen, check your patient first.
Do not treat the monitor. For the correct interpretation of any of the entitled CO2 levels, it's very important to bear in mind that entitled CO2 only agrees with arterial CO2 when ventilation and perfusion are well matched. So both of them play an important role in having great values.
If you've got a large arterial to end total CO2 difference, It quite often will develop when circulation severely compromised, that we go back to, if you've got issues on your CO2 levels, go and check for hypertension, hypervolemia, as was discussed in the previous lecture. In large animal ventilation perfusion mismatches happen quite often, and for that reason, we have to watch very careful for our horses if we do monitoring with ETCO2 and lanography of what's happening to these patients. If you just look at this graph and you can see the change in your CO2 levels just based on your cardiac output.
Your cardiac outputs is adequate, your CO2 levels will normally be normal. Your cardiac output is very low because of hypertension, hypervolemia, your CO2 will will go down. And the moment you address that and treat your hypertension appropriately, your CO2 should respond as well.
One of the factors we quite often forget with capnography is hypothermia. Hypothermia because of invariably giving us bradycardia, invariably, sometimes not giving us, hypertension as well, you will find that your CO2 readings is actually really completely abnormal, just based on the fact that your cardiac output is not adequate. So if we move on to pulse oximetry.
The biggest advantage of pulse oximetry, it's not invasive. And it gives us very good information, oxygenation, pulse rate, rhythm and quality, and very subjective information of pulse quality. So the area under the curve quite often give us some sort of indication of cardiac outputs.
So if you've got a very good, clear graph. With a nice amplitude, you know that in essence your cardiac output most probably is adequate. If you've got the same 95% oxygen saturation, but if you've got a very flat curve, invariably your patients most probably hypovolemic.
So desat saturation is significant. It can happen very quickly and it can be life-threatening. And pulse oximetry has been shown in human and veterinary medicine to be one of the big lifesavers.
And the reason for that is that With our normal eyes, it's not always that easy to see hypoxia. Even cyanosis is not clear to everybody in terms of recognising it, bearing in mind that most often our patients discovered in drapes, this in any case, difficult to get to the patient to actually see this patient is severely cyanotic and you are in desperate trouble. And the pulse oximeter should have warned you a long time ago that you are heading the wrong direction.
So for the mechanism of measurement. We are basically reliant on the difference between oxy and deoxyhemoglobin that is absorbed with different wavelengths, and you've got alternative transmitting wave forms of light. Red of in red and infrared light.
And through this transmittance or reflectance probes, through this pulsatile beds, a photo detector will assess the absorption and will give you the difference between the two. And that will mathematically derive the SPO2 level. So a lot of the monitors that we see.
Will only give us a figure, and the figure is very unreliable. If we don't have associated. Pulse oximeter curve, or associated light reflectance that we can see that we are in the green zone of the lighting and not only in the red zone, although you can get a 99% reading.
So be always cognizant if you do buy a monitor, that is actually working on the patient, because some of the monitors out there will work on your coffee mug as well. So, it normally gives us an indication of how well haemoglobin is saturated with oxygen, not how much oxygen is being carried in blood, nor does it assess adequacy of ventilation or that you need ethnography. So pulse oximeters are accurate between 2 to 3% within the range between 70 and 100%.
They are not calibrated or anything below 70%. And they do not give you BTB changes and SPA2. It's a very small lake, but that's normally not really significant, unless you've got a very critical participation, it, it might become a bit of a problem.
It can be considered as a late indicator of hypoxemia. If a patient is being supplemented with oxygen, sometimes it takes a bit longer for The pulse oximeter because the patient's fully saturated, haemoglobin might be low, but the haemoglobin is fully saturated. The healthy patients receiving supplemental oxygen should have a PO2 of about 500 millimetres of mercury and SP of 100%.
But the PAO2 will have dropped to about 100 millimetres of mercury at this pulse oximetry reading of 95%. So what I'm trying to tell you is that we normally try and aim of keeping your pulse oximetry readings above 95%. So it's 60 millimetres of mercury of your arterial blood gas, you will still have a 90% reading of your saturation.
This means that lungs function will have deteriorated significantly before there's a believable change in the pulse oximetry. And for that reason, If you are working with a critical patient. Doing a blood gas every now and then, just correlating the values that you get might be really useful.
Your pulse oximetry is very useful in patients being transition, especially between room air and oxygen, and and recovery, and patients that are not receiving supplemental oxygen, because I quite often find that you have a patient in theatre, 100% oxygen, you're ventilating him, he's doing perfectly well. You quickly wean him off the ventilator. Before you take him out to ICU or to radiology or wherever.
And nobody at that stage are still monitoring the patient's saturation. And quite often, these patients desaturate in that transfer period. So it's very, very important to continuously still monitoring saturation while you are transferring these patients.
And continuous pulse monitoring may actually be more useful function of the pulse oximetry in most of these patients. So what are our limitations? Well, put perfusion for one.
In the area being monitored by the pulse oximeter, you can have low blood pressure, poor con contractility, vaso constriction that has been mentioned earlier. Remember, if you get peripheral vaso constriction. Our flow during the blood vessels might be slower, and the patient might appear very pale, pale blue, although the blood pressure is still adequate, but pulse oximeters sometimes can struggle to find the pulse because of the peripheral post constriction.
You have to take note of alternative hemoglobins. This doggy is a doggy with me haemoglobin hemia and This is the colour, the cynotic colour that you see here, while the dog is awake. If this dog gets stressed, it goes completely purple, dark black.
If you look at the top blood, you can see it's very dark compared to a normal dog's blood on just a philtre piece of paper. And what we do see is that the pulse oximetry reading in this dog is 81%, just because of the fact that the pulse oximeter can't ascertain that this is hemagamoglobinnemia, that's the problem. The other reason that we have to look out for a struggle to penetrate through hair or pigmented skin.
Over thick tissue bits that increase your non-posit absorption. Hair might also decrease the contact between the probe and the skin. And then your severely jaundiced patients like bilirubin normally do not affect pulse oximetry because it's got minimal effect on your red and infrared spectrum.
But if they immune mediated hemolytic anaemia and they jaundiced, that might actually affect pulse oximetry. Increased level, levels of lipids in the blood may affect pulse oximetry as well. And then any injections of dyes, if your surgeon is going to use a dye to ligate or to identify whatever he wants to ligate, like methylene blue, it can also affect your pulse oximetry.
Then we're looking at pulse vibration and patient movement. It's more a problem in conscious patients. In dentals, it might be a problem, but just try and move your probe to something that's more appropriate.
And sometimes a wet core swab swab can actually Help to secure the probe placement and encourage contact, and quite often you get a better reading. I found a very small patients it's very circustricted if we just place the probe and then we do not get a good reading, or just placing a a wet swap in between quite often that helps quite a lot. So what about ambient light?
The older models had a problem with fluorescent lighting because of disturbing effect, and that could confuse your pulse oximeter. The newer pulse oximeter doesn't have the same problem, but it's really imperatively reported to make sure that your pulse. Probes is actually over the tissue bed, and that halfway on the patient and halfway off the patient, because this will lead to falsely elevated pulse oximeter readings.
So your pulse oximeter will read 100%. But if you look at the graph in this pulse oximeter, it's absolutely nonsensical. It doesn't make any sense.
So it's very, very important to make sure that your entire LED is transmitting through the tissue. As I said earlier on, there's a lot of models on the market, and you have to make sure that whatever you buy is really giving you valuable information. This is two models on the same patient.
And you can see on your left-hand side, gives us a SPO2 reading of, of 77, and the graph doesn't make any sense whatsoever. And then the same patient, just with the proper equipment, you get a 99% reading and a graph which is associated, which is, it's giving you the correct reading. So always, before you buy any equipment, make absolutely sure that what you are reading is actually what you're getting.
I'm going to move on to blood pressure, and we're not going to discuss invasive blood pressure, just for me a bit of time as well, but Doppler inflammatory is one of the things that's cheap, it's easily available, and it's still one of the mainstays for a lot of veterinary practises, although we've got all these fancy multi parameter monitors. So the intention of dooflammatory is that we detect the pressure when the blood flow returns after you've occluded the artery. When that return of flow is detected, it normally gives a systolic pressure, but that is obviously very dependent on the size of the vessel and the amount of flow that's passing through it.
And flow is quite often likely to be detected later at lower pressures in smaller arteries with lower flow. And especially in cats, we quite often find, or most of the literature support that what we see in Doppler is more the mean pressure in cats than the systolic pressure. And once again, we are offered to agonists because of the peripheral vasa constriction.
And the reduced cardiac output and the the associated reduced flow will have an influence as well. It's very valuable in transporting patients because she can hear the swishing sounds in the back of the, of the patient being transferred, and it's very, very useful for trained information. So What is the promises, what is our where our main concerns is, is poor coupling between the ultrasound probe and the patient and variably use not ultrasound gel, ECG gel.
Make sure that you tape it in properly and make sure that you do not have any movement. If you've got a patient that's going to be in theatre for a long time, you might find that this gel actually dry out, you might actually lose contact with the patient because of the gel getting tacky and dry. We still find in a lot of practises that the first cuff that's available is the cuff that's being used.
So, the doctor, the, the veterinarian immediately wants blood pressure. He wants blood pressure cuff. So nobody really checks what is the blood pressure cuff sizes.
And for us the veterinarian anaesthesia, it's a bit of a problem because of the range of patients that we work with. And so it is very, very important that we use appropriate size cuffs, which should be 30 to 40% of the circumference of the leg. Earphones help you to ascertain more return of flow, and once again, noise in theatre, movement in theatre might have an influence on what you're actually reading.
Electromagnetic interference is another thing that have an effect. If you use hotdogs and theatre, they've got quite a strong electromagnetic feel, and you have this audible cracking in the background and noise. So if you want to take a reading, it might be easy just to quickly turn off your hotdog just for a moment or two, do your readings, and then you can turn it back on.
Battery failure is one of the things that creeps up on you because you don't even think about it. You're so used to do it repeatedly, so if somebody doesn't take care of your equipment very carefully, your battery can actually run out during the anaesthetic, and you might actually think there's something wrong with your vision. So it's one of those things, upkeep and monitoring and maintenance of your equipment becomes exceptionally important.
Those little pieces of crystals that is actually transmitting the sound is very, very pliable, and you have to be careful of how you handle them and how you store your equipment. Once again, it goes around carefully looking after your equipment, because the wiring can become damaged, the probes can become damaged, as well as the pieces of crystal as well. So if you look at a telemetric blood pressure measurement, and it's the way most of the human guys do it in theatre, very few of them will place arterial line to do directly arterial pressure, unless it's a compromised patient.
So what we are looking at is a microprocessor that controls the measure inflation and deflation of the cuff. You don't physically manually have to do it. As the flow returns to the artery beneath the cuff, it picks up turbulence of the vessel.
And that causes oscillations to occur. And these small changes in pressure can be detected in by a pressure transducer. So what is our limits?
Quite often we find that ciometrics tend to read systolic pressure, underres systolic pressure, and overread diastolic pressures. And once again, it's very pertinent on which model and which makes you are buying. Mean pressures tend to be the most reliable, as they're taken from a point where the pressure oscillations are at their largest.
So invariably, if we use oscillometry, and we are going to make a decision on treating hypertension hyemia, we'd rather look at trends of the mean pressure than systolic dio solid. Ocillometries relies strongly on regular pulsations, so patients with arrhythmias might give you problems in having readings and the size of the patient and current hemodynamic status. So your circulating blood volume, your cardio function, your vascular motor tone.
It does play a huge role in what oscillations your oylemetry can actually pick up. And it will affect the ability of the telemetry to obtain accurate readings. So smaller patients and those that are hyper or hypertensive are actually the biggest challenge for accurate measurements.
And A lot of practises use human. Equipment, which is not a problem as long as you're aware of what the issues can be with that. The normal human blood pressures.
They, so those machines will use normal human blood pressure to determine cuff inflation. And they often have settings for neonatal paediatric and adult patients which you can pre-select. And that will alter the amount of pressure that the cut will actually inflate to.
So the patient type. And for us, that becomes a problem because human neonates have much lower blood pressures than our smaller adult veterinary patients. So, invariably, the artery isn't actually occluded, and you will get a false reading.
And that's why often in these patients, the monitor will time out because it can't get a reading because it isn't actually inflating to the to enough pressure to occlude your blood vessel. So cuff sizes are very important. We normally look at 40% of the circumference of the limb, that's normally about 30% of the circumference of limbs.
If the cuff is too narrow, it tends to overread blood pressure as the cuff is not wide enough to properly occlude the artery. If it's too wide, It reduces the flow through the artery and with the increased resistance, it tends to under read. And this error tends to be greater with two smaller cuff than too large a cuff.
If you place a cuff under two Velcro parts, Overlap easily. Normally, that is the correct size, the correct size for that patient. The other easy way of looking at sizes as well if you've got tape measured, you've got both centimetres and inches on.
If you turn, if you measure the inches, you turn around, it will give you the size of the cub. So 2.5 inches will give you a size 5 calf.
So it's very easy to get a very, soft band quickly wrapped around the leg and see what is 40% of the circumference of the leg, because it does make a huge difference in these patients. Interval of reading plays a role as well. Invasive blood pressure monitor does not give you B2B changes in blood pressure.
It gives you a snapshot at regular intervals. So, your blood pressure can swing rapidly in a crisis, and therefore, non-invasive blood pressure monitors may be less reliable in very critical patients. The timing between measurements in using both techniques is important.
If your interval is too short, the blood flow through the artery might be actually impaired, which also leads to lower blood pressure reading on subsequent measurements. So, invariably, cycling should be set at least between 2.5 to 3 minutes to avoid this.
Most of your cuffs will have a little arrow that should be overlying the artery, because that will be the best place to detect the pressure and the oscillations. And you try normally and place it over a non-compressible appendage if possible, a circular appendage as possible. And and your horses and cats, quite often the tail the tail works very, very well as a circle circumference.
To be able to read it In our bigger patients, it's also important to understand if we've got a high difference between the base of the heart. That 1, 10 centimetres above the rate of atrium will underestimate the blood pressure by 7.3 millimetres mercury.
And 10 centimetres below the atrium will overestimated by the same amount. So once again, if you've got a large animal, you place the cathetic patient's lateral recumancy, be cognizant of the level of the heart and adjust it accordingly. It normally is not as critical as small animals, but it does make a huge difference in how bigger animals like horses.
So what do we do when we get abnormal readings? So in this patient, the ECG is reading 44, the pulse oximeter is reading 103. So obviously there's a big discrepancy.
For me, the most important part is assess the patient, check pulses. Check respiration, check your patient's colour, ascertain what's happening with your patient, compare and cross-reference all the monitors that you've got available before you make a decision to treat that patient. So I think if we take note of these pitfalls, we take note of how these machines actually get the values that they present to us.
It will ensure that adverse events are not missed, or that crises are rapidly identified and treated, and that no interventions are made unnecessary because you can quite often do a lot of harm by treating a patient that didn't require that treatment. So, I know I talk very fast, so if you've got a lot of questions, I won't mind, but thank you very much for your time and patience. Lynette, thank you very much for that very insightful talk and well done on picking up your stride in the beginning after computer crashes and everything else.
That really was very informative. Thank you very much. At this point, we don't have any, questions coming through.
Folks, if you do have a question for Lynette, please feel free to, type it into the question and answer box and, we can then, ask it and she will happily answer those questions. Lynette, I just wanted to ask you about, when you were talking about pulse oximetry, they did lose favour a few years ago where people were, sort of saying things of, oh well they euthanize dogs and, and the pulse oximeter just kept on going and that. I think it's quite important, your statement there about the range between 70 and 100% accuracy.
Because that's what gives them their, their sort of bad name, as it were. Yeah, in essence, that's why it's so extremely important to understand what you are reading, how the machines are actually obtaining those values. And then patients that, especially patients that was in theatre, and for a long time, they've been oxygenated for quite a long time.
They've had fluids for quite a long time. So even though they're clinically dead, you might still find that haemoglobin saturation is still picked up. And that's why it's so extremely important that if you get a specific reading, for example, 90 or 95%.
That you do have an associated curve, because you might have a 95% reading, but if your patient is clinically dead, you will have a flat line in terms of the curve. Or if you had those light bars, the light bars would be in the red zone and not in the green zone. So yes, but there are also monitors out there that you can put on your coffee mug, and it will give you a reading of 9.
It's prudent to go and see what you're actually buying. But for that reason, yes, it fell out of favour. But a lot of the literature research in human medicine, what made a huge drastic advance in human medicine and patient safety is pulse oximetry, because it's easy, it's cheap.
And really for me, It's something that's very, very useful, especially at the moment you transition a patient from theatre to radiology to ICU just because in that period of time, quite often, yes, he's breathing spontaneously, but his total volume might not yet be adequate. And those patients quite often I think. People don't realise that we lose patients in ICU because of hypoxia more often than anything else.
Yeah, I think I I remember many years ago reading a a a statistic that said that somewhere around 60 or 64% of anaesthetic deaths occurred in the immediate post-operative period. It's absolutely that because quite often, we stop all the monitoring that we've done in theatre because you have to move the patient, you have to quickly do post-operates. I mean, it's just that period.
I mean, the horses are even worse because you disconnect everything. You disconnect oxygen, you disconnect fluid, you disconnect blood pressure support. And so quite often those guys they, although they're breathing normally, the pulses feel fine, they get hypoxic and we don't even realise that.
Yeah, I also liked your statement about treat the patient and not the monitors. You know, it's one of those invariable things that, as I mentioned initially, our anaesthetics can become hours and hours of boredom of watching normal stuff happening. And then suddenly there's a crisis and you get this sheer panic, you get a flat line.
And the first thing you want to do is start immediate CPR, but it might really just be a disconnection. So it's imperative to make sure your patient's heart is beating, the patient's breathing, and aesthetic plan is correct before you start instituting cardiac, hormonal resuscitation. And people quite often in that spur of the moment, overreact.
And that's why the alarms is an issue, and I know I hate alarms in the background. Some surgeons really detest them. But if you do disconnect your alarms, your monitoring does have to be so much more careful that you're not missing real crisises or real incidents of problems, but you also don't overreact if it's something that's easily solvable.
Yeah, absolutely, absolutely. Right, well, we've come to the end of this, anaesthesia session, to our three presenters, Kieran, Leon and Lynette tonight. Thank you all very, very much for your insightful information and certainly I know for myself, you have given me information to go back and and assess and look at and certainly consider.