S7 Ep. 6: Take my breath away, part 1, re-release

Today's episode is sponsored by TIGO. For most of us, indemnity insurance is one of our biggest cost of practice. But when was the last time you took a look at the coverage and compared your premium with others? Many of us are still with the same insurer we joined in Med School or Intern year. Thousands of doctors have made the switch to TIGO and benefited from their personalized approach to pricing. You will also get an extra two months free in your first year. If you were new to private practice, you might even qualify for four years of discounted premiums. TIGO offers competitive premiums, quality cover and 24/7 support backed by top medical legal advisors. Get a free quote and discover why thousands of doctors are insured by TIGO by visiting TIGO.com.au Hello listeners and welcome to DeepBreaths, a podcast covering topics related to the part to an aesthetic exam. I'm Dr. Kate Steele and today's episode is take my breath away part 1. We will discuss a few cases involving one lung ventilation with special guest Dr. Ivan Rappchuk. As always in this podcast, we represent our own views and not those of our employers or Ansgar. Now those of you familiar with our podcast may have heard Dr. Rappchuk's calming Canadian words in previous episodes about cardiac pulmonary bypass in season one and intra-aortic balloon pumps in season three. If you haven't had a chance to listen, be sure to make time because they're great episodes that cover a lot of worthwhile contact. Dr. Rappchuk is the director of the Prince Charles Hospital Department of Anesthetics and Perioperative Services and works publicly in cardiac anesthesia as well as privately with Northside anesthesia. As well as this, he directs both the pre-anesthetic clinic and the acute pain service at the Prince Charles, but Dr. Rappchuk's crowning glory is that he coaches the Queensland State ice hockey team and hopes one day that ice hockey is more popular in Australia than it is back in Canada. Ivan, thanks for joining us on deep breaths. Very happy to be here again. Thanks for having me back. Excellent. Thanks for coming. So look Ivan, I'm going to level with you here. I've always found thoracic cases and one lung ventilation in general to be quite anxiety-inducing as I've really had good experiences with what I know are to be fair, quite an unwell group of patients with very limited cardiac respiratory reserve. So I'm looking forward to having my fears swept away like a puck on the ice. I will do my best to calm many fears. Excellent. Excellent. Well look, let's jump straight in with our first case then. A 68-year-old man is scheduled for an open, right-uplobectomy on your list tomorrow for a T1N0 non-small cell lung carcinoma. He is an active smoker with a 30-packier history but has cut down his consumption from 20 cigarettes daily to five. He has moderate emphysema but walks two kilometres daily on flat ground without any issues. Other comorbidities include hypertension on hypercholestrolemia. He is 1.78 meters tall and weighs 89 kilos giving him a BMI of 28. His list of medications includes Candice Arton, 5 milligrams daily, a Torvastatin, 20 milligrams daily, aspirin, 100 milligrams daily, teotropium, bromide, 1 single 18 microgram capsule inhaled daily and salbutamol on an as-needed basis. Now Ivan, is there anything else you want to know about this patient before you can make your anaesthetic plan and start the case tomorrow? Well look, the patient's coming through thoracic surgery often have a range of medical problems that need to be assessed. There's numerous papers and protocols on the suggested preoperative workup of these patients and nowadays there's actually lots of stuff coming out information and otherwise on early recovery after thoracic surgery or ERATs protocols. I've seen that, yeah. And they're developed specifically for thoracic surgical patients but with that being said there's definitely some major points to consider in a patient coming for thoracic surgery with lung cancer. Now I know we'll talk about Peter Slinger and his sort of seminal statements and papers on preoperative lung assessments at some point but I can't help myself in emphasizing the work of another top notch Canadian anesthetist. Yes, Slinger works at University of Toronto and his preoperative workup is actually still what I think about for lung cancer patients. Actually I will say I think about it for all cancer patients for that matter. Slinger spoke of the foreMs, mass, medications, metastases and metabolic syndromes and I still go over these things in my mind before any cancer patient. So for mass these are the direct effects of the tumor and the nodes on the surrounding tissues and the three main things that I worry about being compressed are the tracheobronchial tree, the superior vena-cava causing SVC syndrome and the pulmonary artery. Now there's other things you have to consider for mass effects. There's post-abstructive pneumonia which can cause lung abscesses and there's chest wall extensions specifically those that can lead to panco syndrome or even possibly laryngeal or or phrenic nerve palsies. So that's the mass effects. Then there's the meds, the medications. Now a lot of these patients we're seeing are coming in on preoperative chemo nowadays. This has to be considered. I think for the examines they should be knowledgeable about blyomycin and cisplatin because those have been used in the past and are often asked about. To be honest they're not actually being used a lot nowadays but they're the most key ones that they may ask to get asked about in exams. Okay and they used for thoracic tumors. Exactly. Yeah. So there's a lot of platinum-based ones now used and steroids but the key ones in the old days often examined on are blyo and cisplatin. Okay good to know. Yeah. Then there's the meds. Yes. Now most surgical patients for lung cancer don't have metastases. That's why they're coming for surgery. So this has been ruled out prior to proceeding but we have to keep in mind that it can occur and lung cancer preferentially goes to the brain to the bone to the liver and to the adrenals. So you got to really keep an eye on those areas for any preoperative patient. And then finally there's the metabolic syndromes. Usually these are with small cell cancers which are nonoperative but they can be seen with the non-small cell as well. These are the things like SIADH, PTH like peptide being produced leading to hypercalcemia and Lambert Eaton syndrome. So those are the big 4M's that I worry about. And there's all the other things that come with any other anesthetic, medical history, allergies and keeping in mind that these patients often have a long smoking history. So beware the lung disease and beware cardiac disease. Good advice. Yeah. Then I based some investigations off those 4M's. So chest x-ray, CT chest, these are often done for us. Good for the location and the size of the tumor. Pet scans are often done to see if there's any nodal involvement or mets. And then RFTs are really key for thoracic workup. Looking at pre-existing lung disease. And you can even do fancy things like flow volume curves upright and supine if you're thinking of any potential mass effects on the trachea brokyl treat. Interesting. Now we've touched on this previously but how relevant is sling as three-legged stool to current practice? And I'm curious, do you still use it in your pre-operative assessments? Look, the surgeons are actually really good at risk stratification nowadays. They're very good at it. And we generally don't see as many marginal patients as we used to. But that being said slingers three-legged stool is still very, very relevant. And I consider it in all my pre-operative assessments. So his approach took the three-legged stool to look at a stratify patient's risk and then identify factors that can be managed to improve their outcomes. Looking at three main things. The first is lung mechanics. And spirometry is the main thing here, specifically the FEV1. Then there's perencable function of the lung. This is the lung's ability to exchange gas. So diffusion studies are the key here or an arterial blood gas on room air is also helpful. And then the final of the three-legged stool would be the cardiopulmonary interaction. And you can do formal cardiopulmonary exercise testing. Most of the time nowadays we just send people for either a six-minute walk test or to see if they desat on exercise. That's interesting. Now on that note we're actually not going to cover slingers three-legged stool in this episode because we're focusing more on one lung ventilation. But we have included a really useful link in our episode notes for anyone wanting more information. So Ivan, what's your anaesthetic plan for this patient? Well one thing that's necessary to know is the surgical approach. More and more thoracic surgery nowadays is being done by vats. So yeah, to have a good discussion with your surgeon. That's the key. But this one, let's say the patient's having a thoracotomy as discussed. So general anesthesia with lung isolation and then a thoracic epidural. Now there's other regional techniques. We're not going to get into them right now. But for a thoracotomy you would still think that a thoracic epidural is the gold standard. And then looking at that M-A-D-E approach or the made approach with monitoring, have some standard ants come monitoring, and adding in an art line. I usually put the art line in the dependent side when you think about the lateral so that it positions well. I generally don't put a central line in for any thoracotomies. There's none of them for numenectomies. Then in A, the assistance. Look, this is key. Having a tech or a nurse who is very familiar with thoracics, knows what they're doing. Absolutely. Absolutely key. The drugs, induction drugs. Well, generally you put the patient to sleep with a standard manner of opioid, propofol, muscle relaxant. The question then arises as what to use for maintenance. Tiva, volatile. I don't want to get too deep to it here because that is an absolute rabbit hole. There's zealots on both sides. Tiva is good because it doesn't affect hypoxic pulmonary vasoconstriction very much. Less nausea, vomiting, less confusion after. But the other side, there's some data to suggest that lung injury may be limited by using the vapors. So I just tell people use what they're comfortable with. Or if you want to use what's best, then use Tiva. Oops, zealots speaking. Oops, a daisy. Did you slip that in? I just did anything. And then of course have some uppers and downers ready, especially if you have a regional approach that you're going to use. You'll often need some uppers on hand emergency drugs. I don't have anything out of the ordinary. In fact, I tend to pre-draw less and less up nowadays as I get older. Maybe as I get even older, I'll start drawing up more and more again. Maybe time will tell. And then equipment. Large bore IV, remembering though that thoracics is not really a blood-losing procedure most of the time, although a big IV is good to have when they're going around the pulmonary vessels. And then DLT, a double lumen 2, left or right, again, which side of this spectrum are you on? Topic of controversy. Most anesthesiologists will go with a left whenever they can because it's probably easier to place, although the literature would suggest that in the hands of someone who does a lot of DLT's that a left and the right are placed as effectively. And then a bronchoscope. Although if you have the Bivocyte DLT when they're available, you don't have to use the bronchoscope, but it's probably helpful. Now on the topic of double lumen tubes, how do you determine the correct size for your patient? It's a good question. There's no firm hard and fast guidelines on this. It's really dependent on the individual practitioner and the patient. And I will mention that there are some studies. A lot were done on sort of middle-aged white males. And what works for them. So not that society would ever base anything on bias towards that group. So be wary of the numbers given out in women and non-cocasions, especially Asian population. It's been shown that the tubes can be too big in those individuals. But usually we base it on the sex, the height, the bronchial diameter, and then the type of surgery. For type of surgery, I know for me if I'm doing lung volume reduction surgery or a thoracic aneurysm, I do like the biggest tube I can for effective suctioning and low resistance to breathing, especially in the lung volume reduction you can with small tubes get auto-peep. Otherwise, male patients, generally if they're heights over 170 centimeters, they'll be a good fit for a 41 French DLT. If they're between 160 and 170, good for a 39 French, and less than 160, 37. Okay. If we size it based on the patient's bronchial diameter, a bronchial diameter of greater than 12 millimeters fits a 41 French. Okay. 12 millimeters for a 39 and 11 for a 37. Okay. 10 for a small 35. Okay. So you can measure that best on a chest x-ray. Okay. Or a CT. CT probably best. Yeah. Okay. Um, nice. That's good advice. Yeah. Females? Yes. When you're choosing a DLT based on height, generally if they're taller than 160 centimeters, they can fit a 37. And if they're from 150 to 160, 35. Okay. If they're shorter than 150, you just generally drop either to a 32 or struggle to get a 35 in. Okay. And I mean, as we do with standard tubes, we usually pick a size and then have a few backups available. Yeah. And I'm guessing you would do the same thing as so. Same thing. Okay. Get one ready and have a couple of in the room, usually one up and one down in size. Okay. Absolutely. Now you mentioned that there's that we have to be wear sizing Asian populations. Do you just reduce the size that required for both males and females in those of that particular racial trait? Yeah. Look, I generally do. And it's also a young people. I find younger people probably because their airways aren't as big as some of the older people who've smoked for many, many years. Okay. I often air on the, if they're right on the fence of sizing, I go on the smaller side. Okay. Fair enough. That's good advice. So I've announced the following morning and our patient has a 16 gauge cannula in, a radial outline and a thoracic epigural and has just been enthused. And he's easy, he, she, I can't remember. They are easy to brake us mentally without any airway adjuncts. Now what process do you go through to insert a double-women tube? The first thing I've done is before that I would have prepared my DLT. Okay. They usually come in the package completely straight. Okay. And so I ensure that the both the tracheal and endobronchial cuffs are completely deflated. So I don't get any loss of view of my cords. And then I put a curve that's adequate into the tube. They're pre-styleted. So we ought to make sure that they're, they're curved for insertion. Okay. If I'm using a vivasite, I also make sure I put antifog on to the camera prior to inserting it. Makes sense. So it doesn't fall out the camera with secretions. That's fair enough. Then I go direct laryngoscopy. I insert the tube through the vocal cords and I stop. I then brace my hand sort of on the patient's cheek. And I hold the tube and have my assistant take out the sti-let. Okay. Yes. You don't want to advance it with the sti-let in. That's a high likelihood of causing some sort of tracheal trauma. Once the sti-let's removed, I rotate the two slightly more than 90 degrees to the left. If it's a left double lumen and advance it gently until you feel a little bit of resistance. That's the other way is to advance it to a predetermined depth. Okay. It's been suggested that if you take the patient's height in centimeters, divide it by 10 and add 12, you'll get the proper depth of insertion. So for a 180 centimeter guy, 18 plus 12, 30 centimeters deep would be about where you put it. Okay. Most of us would just advance it till it has a bit of gentle resistance. That's normally when you're into the left main stem broncus. Okay. So we've advanced it. If we've hit that resistance, then what do you do? Then the thing, I generally just check and make sure it's in the trachea. I put them on the ventilator and I get out my broncus go. Okay. Checking a double lumen tube, there's two real ways to do it. One is clinical checking and then one is bronchoscopic. Okay. The clinical way, you actually clamp off alternatively the two lumens after the end of bronchial cuff is inflated and you watch for chest rise or listen for chest rise. I will admit that I omit this mostly in my practice. Fair enough. I think going straight for the bronchoscope is where the money is and if you just clamp off the tracheal lumen, go down the tracheal lumen with your bronchoscope, you can see if you're in the correct side or not. Yeah. And then you can see how deep you are to make sure it's perfectly positioned. I imagine that would give you a better indicator of how your tube is positioned than just looking at chest rise and fall because that can be unreliable, depending on certain situations. Absolutely. And you can imagine the patient population you have patients with often quite bad COPD or restrictive lung disease, their lung sounds and their chest wall excursion is not exactly the best to begin with. Never mind when you're trying to check clinically in a noisy operating theater. So for me, yeah, I just, I use clinical testing when I have a trainee with me, but if I'm by myself, I move straight to bronchoscope. Fair enough. That's understandable. Now I just want to clarify, so after you initially insert the tube, do you inflate any of the cuffs before you put them on the ventilator? Generally, I check with the bronchoscope to make sure I'm in the correct side. Okay, before you start it. Before I start inflating cuffs, if I'm going to check clinically, I put the bronchial cuff up to isolate. Okay. Most patients who are elective, it doesn't matter if you ventilate both sides. Okay. If there's a urgency to getting lung isolation, then I do that immediately. But in an elective case, it's not critical to do it right away. Fair enough. And is there any situation where you'll have just the tracheal cuff up and not the end of bronchial cuff? Not usually. Some cases, I mean, look, the most common would be if you use a left double lumen for a left numenectomy where you don't need to get isolation specifically of that side. But most of the time you would put up both cuffs. Okay. Okay. Cool. Okay. So our double lumen tube is in. It's well positioned and it's secured. And the patient is now in the lateral decapitus position prepped and draped. Surgery has started and the surgeon asks you to isolate the left lung. Now, how do you go about doing this? Okay. Well, look, once they're in the lateral position for me, the sooner you isolate the lung, the better for the surgeon. Anyway, because the lung obviously has to deflate. So I clamp off the upper lumen of the double lumen tube and then I open up the valve at the top of the tube to allow the air in that non-ventilated surgical side to escape, allows the lung to collapse. I generally change my ventilation at this point as well. I change it to pressure control or even better. I use PCVG nowadays to minimize pressure injury to now our single lung that we're ventilating. Yeah. I also tend to try and decrease my FiO2 to avoid any hypoxic injury to the lung at this point as well. Okay, cool. That's good. So, look, surgery, we've isolated surgeries, progressing is expected. But you start to notice the patient's oxygen saturation is slowly drifting down. The sets are now at 80%. What's your approach to this problem? The classic desat on one lung question. Get ready for this on the exam. Absolutely. This is classic exam photos. Yeah. Well, the first thing to do is it's important to understand that this is very common. A lot of patients desaturate on one lung. About a third of patients, in fact, undergoing one lung ventilation experience hypoxemia at this time and it usually starts to occur. But a couple minutes after you've gone on one lung ventilation, once that oxygen reservoir in the non-ventilated lung has been absorbed, this changes in the blood flow that add to the decrease in oxygen saturation as well. When we put the patient in the lateral position, prior to beginning surgery, there's a change in the way the lungs are perfused. So, the dependent lung now gets a greater proportion of cardiac output from the right ventricle. And even though we're not ventilating the left lung, or the upper lung, about 20 to 25% of the cardiac output will continue to pass into this lung. And this is shunt. And that obviously helps make the hypoxemia worse. So, as the lung collapses, however, the shunt does get reduced. And again, what happens is hypoxic pulmonary vasoconstriction starts to kick in. And in this instance, we actually often see a slight rise in the oxygen saturation again. Okay. As that shunt is decreasing. Yeah, that's exactly right. So, from here, we need to troubleshoot, though, whether the hypoxia is just due to this sort of changes in the regional blood flow of the lung, or if there's something else going on. Okay. So, the causes of desaturation, look, the first one changes in the lung function with impaired oxygen delivery. So, is it a ventilation problem? So, you can have oxygenation problems, you have shunt, you can have segmental bronchial obstruction with secretions in the dependent lung, you can have reabsorption of the residual oxygen from the non-dependent lung that then leads to an increased shunt. Cardiac output could be a problem. So, this can lead to desaturation. And these are the main culprits with cardiac output, the main issues being patient position, the vasodilatory effects of the general anesthetic, or the vasodilatory effects of your regional anesthetic. Yeah, very true. Yeah. So, you can have a ventilation problem, or you can have a placement of your double lumen tube problem. Yeah. This is actually pretty common, especially in that flip from supine to lateral. And the best way to check that, obviously, is bronchoscopy or vivocyte? Just to interrupt quickly. When you pop someone in that lateral de-cubidus position, do you bronch them again before they start? Absolutely. Every single time. Excellent. Okay. Even if you don't have a drop in your saturation, or you don't have a change in your airway pressures, which can be significant for a tube moving, you always should check your tube position flipping from supine to lateral. Yeah. Because at least then you know before they get dragged in your access card. Absolutely. Absolutely. Okay. Cool. So, we mentioned the ventilation problem. Yes. We mentioned the placement of the double lumen tube problem. Then there's a physiological changes that occur during one lung ventilation. So, we got shunt hypoxia. Yes. That non-dependent lung, the operative lung, blood still flows through it. The things that help out with that, there's gravity. So, the lateral position is actually a really good thing for one lung ventilation, because it causes flow to go preferentially to the ventilated lung. Surgery, surgeons actually help us here, because as they compress the lung and retract things, they squeeze that blood back to the ventilated lung on the bottom. Okay. And then as they ligate different blood vessels off, this helps us as well. So, it causes blood flow to go away from the surgical lung to the non-dependent lung. And then finally, I guess you get, you get HPV, hypoxic pulmonary vasoconstriction. And this will decrease blood flow to the operative lung, the up lung, by about 50% in a lot of cases. That's significant. It is pretty impressive. Yeah. Yeah. So, I guess one other thing to mention would just be the pathological processes that you got to keep in the back of your mind. Yeah. So, there is the idea that a lot of these patients have lung disease, ventilating them on one lung, especially if it's relatively higher pressures. There's always a chance of something like a pneumothorax. Yeah. So, just keeping that in mind as well. Yeah, fair enough, that's good advice. Yeah. So, look, oh, sorry, I was going to say-- No, no, no, no, not at all. Sorry, I didn't mean to interrupt you. No, that's fine. I was just going to say what my normal plan is when the sat starts to drift. Yeah, absolutely. The first thing I do is I check position of the two. That's the number one thing, bronchoscope or vivocyte. If you're lucky to have one in, check that out. Then I suction the lower lung, making sure there's not secretions in that lower ventilated lung causing problems. Then I kind of focus on my cardiac output and optimize that. A little bit of squeeze, making sure my cardiac output and my blood pressure is adequate. I then turn up a little bit of FIO2 to the ventilated lung. And I add in some oxygen to the nonventilated lung. Okay. So, you can do this, this couple of ways, the very simple way is to put the suction catheter down the lumen on the top of the double lumen tube, the surgical side, and just insufflate kind of two to four liters of oxygen through that suction catheter. Yeah, that'll hopefully get rid of some of the some of the problems. If not, you can actually put CPAP on the upper lung. Usually, if you really want to do it, you can do a kind of modify a maple sin circuit to do it with with the maple sin bed. You can put about two to five centimeters of water on the upper lung. Cool. Yeah. And if that doesn't work, I put peep on the lower lung. Okay. I know for me that's, I read about peep being used a lot, but I'm always very wary about auto peep. Okay. And also pushing blood flow by high pressures now away from the ventilated lung. So, peep is my last thing. Okay. So, you don't routinely put people on that. I don't routinely know. Especially in the population that we're usually seeing in this type of thing. Yeah, that's fair enough. So, Ivan, would your approach to a problem like this, a desaturation, be different if it was more rapid? Yeah, look. Okay. The first thing I would do then is I would do a number of these things at once. While checking the two position, I'd turn up the oxygen, I'd give a bit of presser, I'd get my anesthetic tech to get me some O2 tubing that I would attach to a suction catheter and put it down the lung, the non-ventilated lung. And I would let the surgeon know that I'm struggling and that we might have to give a little bit of CPAP or a little bit of ventilation to that lung that they're operating on. So, while the stepwise process is the same, in a lot of ways, you would do multiple things all at the same time. Yeah, that makes perfect sense. Out of curiosity, is there anything the surgeon can do in that situation to improve things? There is. There's let you ventilate the lung. That's right, that's a key. There's very few absolute indications for one lung ventilation. And in reality, none of them are surgical. Yeah. Vats has often been said to be an absolute indication, but I've done vats in spontaneously breathing patients on an LMA. So, you do not need lung isolation, especially with a quality thoracic surgeon. So, but the one thing they can do is they can clamp off the pulmonary arteries or some of the segmental pulmonary arteries on the side thereon. Okay. Now, I'll just get rid of the shunt. Yeah, that's very true. That's very true. But look, I think, you know, just to quickly rehash, figure out the causes, make sure there's nothing bad happening. Yeah. Make sure there's not a new with thorax. Make sure there's not a complete displacement of your double lumen tube. Turn up your FIO2, confirm things with a bronchoscope, suction the ventilated lung, and ensure there's an adequate cardiac output with some presser or some effigrin if you want. Then add some CPAP to the up lung, and some peep to the lower lung. Nice. And worst case scenario. Talk to your surgeon. Talk to your surgeon. So, back on to lungs or have him clamp something off. Sounds good. It's a good approach. It's nice and succinct. I like it. So, look, Ivan, I know this tends to happen a lot when you join us on this podcast, but we've run out of time. Would you? And that's not a personal attack. I actually really like that. So, would you like to join us for another episode to continue our case discussion? 100%. Fantastic. So, look, that was a great first case on today's episode. As always, if you have any questions, comments or suggestions or you just want to say hi, you can email us on [email protected]. We love hearing from our listeners and are grateful for all the suggestions to date. Be sure to recommend us to your colleagues and for consultants and fellows, don't forget to claim CPD. Thanks for listening and we hope you can join us next time on deepbreds.