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Sustainable Anesthesia with Kori Martodam · Style Points

0:00
Hello anesthesia enthusiasts and welcome to another episode of Style Points.
0:14
Today Nate Moore is joining us to present his final RSI as he is no longer a resident
0:20
as of this recording.
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Fortunately, however, he is joining the University of Cincinnati as a faculty member and will
0:26
continue to help me with the podcast.
0:28
Now he's going to talk to us about liver disease classification.
0:32
Nate, take it away.
0:35
When I first saw the word MASH in a patient's chart, I assumed it was either a funny misspelling
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of NASH, as in non-alcoholic steatohepatitis, or an oblique reference to an 80's sitcom.
0:48
When I saw it a few more times I did some digging and realized that a whole new diagnosis
0:52
had been invented that I didn't know about.
0:54
Is this what getting old feels like?
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To save you the embarrassment that I felt, and to help you make the right clinical decisions
1:01
for a patient with a strange new diagnosis in their chart, I'll tell you what I learned
1:05
about the new terminology for steatotic liver disease.
1:09
First, what is it that we're trying to classify?
1:12
The core pathophysiologic mechanism that we're trying to describe with all these definitions
1:17
is steatosis, which refers to the accumulation of excess fat within the liver.
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This excess fat causes hepatic injury via multiple incompletely understood mechanisms,
1:28
but the end result is an increased production of scar tissue within the liver, leading to
1:33
decreased liver function and ultimately cirrhosis.
1:36
Traditionally, the term for liver disease related to steatosis has been fatty liver
1:41
disease.
1:43
The association of alcohol use with the development of fatty liver disease has several medical
1:47
and societal implications.
1:49
Thus, fatty liver disease has traditionally been divided into alcohol-related liver disease
1:55
and non-alcoholic fatty liver disease.
1:58
However, there are several potential problems with this terminology.
2:02
While this binary definition, alcohol vs. no alcohol, is simple, it doesn't always
2:07
do a good job of capturing the complex range of conditions that can lead to hepatic steatosis,
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particularly in terms of describing how varying quantities of alcohol use can contribute to
2:17
liver disease in the setting of hepatic steatosis.
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Furthermore, the use of the terms alcoholic and fatty can be considered stigmatizing,
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which can negatively affect patients' interactions with healthcare systems, whether they choose
2:31
to interact with healthcare systems at all, and affect their ability to discuss their
2:36
conditions with their friends and family members.
2:39
To improve how we talk about liver disease, the American Association for the Study of
2:43
Liver Diseases, the AASLD, has proposed a single overarching term for fatty liver disease,
2:49
which is steatotic liver disease, or SLD.
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Steatotic liver disease is then divided into several subcategories.
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The first is metabolic dysfunction-associated steatotic liver disease, or MASLD.
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This is most easily linked to non-alcoholic fatty liver disease in the previous terminology
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and describes the state in which cardiometabolic risk factors, such as obesity or diabetes,
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are the definite drivers of a patient's hepatic steatosis.
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On the other end of the spectrum is alcohol-associated liver disease, or ALD, which closely mirrors
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the previous alcohol-related liver disease and identifies the use of alcohol as the definite
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driver of a patient's liver disease.
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In between ALD and MASLD lies metabolic and alcohol-related liver disease, or MET-ALD.
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MET-ALD is intended to describe how various quantities of consistent alcohol use can occur
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in the presence of cardiometabolic risk factors, and is therefore divided into MASLD-predominant
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MET-ALD and ALD-predominant MET-ALD.
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The AASLD has created a set of diagnostic criteria to help decide where a patient falls
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within this classification.
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Once a patient is known to have steatotic liver disease, usually diagnosed by imaging
4:11
findings or a biopsy, it is then determined whether they fulfill at least one out of five
4:16
cardiometabolic criteria.
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There are some exceptions, but the major criteria include a BMI greater than or equal to 25,
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an A1C level greater than or equal to 5.7%, a blood pressure greater than or equal to
4:29
130 over 85, triglycerides over 1.7, or an HDL less than or equal to 1 in males or 1.3
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in females.
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If a patient fulfills at least one of these criteria and has no other known causes of
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steatosis, they are diagnosed as having MASLD, metabolic dysfunction-associated steatotic
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liver disease.
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If they fulfill none of these cardiometabolic criteria, then they'll receive a diagnosis
4:54
specific to their type of liver disease.
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This will frequently be related to alcohol use and thus termed ALD, alcohol-associated
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liver disease.
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If a patient fulfills at least one of the cardiometabolic criteria, but also consumes
5:09
a significant quantity of alcohol, they are diagnosed as having MET-ALD, metabolic and
5:15
alcohol-related liver disease.
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They then receive a diagnosis based on the quantity of their alcohol use.
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If the predominant driver of the patient's liver disease is considered to be alcohol
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use, they receive a diagnosis of ALD-predominant MET-ALD.
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If the predominant driver is instead considered to be the patient's cardiometabolic risk
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factors, the diagnosis MASLD-predominant MET-ALD is used instead.
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There are no specific threshold quantities of alcohol use recommended by the AASLD to
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make this determination, but they state that the predominant driver within MET-ALD can
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change over time for a specific individual.
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These classifications, MASLD, ALD, and MET-ALD, are the predominant categories under the SLD
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umbrella.
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There are two more classifications, specific etiology SLD, which covers some more zebra
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diagnoses, and cryptogenic SLD, the fancy way of saying we don't know why someone has
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liver disease, but the specifics of those lie outside the scope of this segment.
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What's important is that you now know the new SLD terminology and can confidently pre-op
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your next patient with liver disease.
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Thanks Nate.
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Corrie Martedon is a certified registered nurse anesthetist who works with me here at
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the University of Cincinnati.
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She obtained her BSN in nursing here at the University of Cincinnati, her master's in
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sciences and nursing at Rush University, and her DNP at Johns Hopkins in 2023.
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She packs her lunch in a bento box every day and enjoys wearing colorful scrub caps.
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Corrie, thanks for joining us today.
6:53
Thank you.
6:54
I'm glad to be here.
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So I wanted to start off with one of my standard get to know you questions, the start of SOC.
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If you could have dinner with anyone in the world, now this could be somebody from the
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past or from fiction or anything, who would you have dinner with and why?
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My mind goes totally blank when you ask that question.
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But it's not for a lack of amazing people in this world.
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It's just real hard to choose.
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So let's see.
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Okay.
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We are here in the middle of July and we're well accustomed now to this summer heat and
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dinner looks like barbecue in the backyard.
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Sounds good to me.
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My sister and her husband bring over two bottles of wine and a crate of peaches and the kids.
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And my friend already has like 16 giant zucchini squash handpicked from their garden that they
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don't know what to do with.
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And the neighbors come over with all their kids and potato salad and dinner is joyful
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chaos and a sheet cake topped with blueberries at the end.
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And my guest arrives as the kids are splashing around in the inflatable pool and the grown
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ups are thinking about getting everyone home and off to bed soon.
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But he's not late to the party at all.
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He's just in time to catch everyone in that loose moment between finishing and leaving.
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And it's Neil Young.
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Neil Young.
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Excellent.
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Is he going to be performing for you or what?
8:21
Yep.
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Yep.
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He shows up with his guitar and a harmonica and he sits in a chair on the back patio and
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plays Harvest Moon with the fan turning slowly above his head.
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My brother-in-law asks my sister to dance and there's the way she smiles at him, which
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is maybe a little too rare amidst the context of running a house and being a nurse and raising
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two kids.
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But tonight we all get to fall in love a little bit again.
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Well that is a lovely picture that you've painted for us.
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I can very much imagine that.
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As long as there aren't too many mosquitoes out, that sounds like an ideal sort of backyard
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fun time.
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Yeah.
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Yeah.
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For sure.
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So let's dive in a little bit more to talk about what we wanted to talk about today.
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You wanted to talk about using propofol as a main anesthetic agent as opposed to using
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gas.
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Can you tell me a little bit more about why that's a big deal, not just for the environment,
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but for our patients too?
9:23
Tell me more.
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I'd be happy to.
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Using propofol as the primary anesthetic agent is a big deal for patients because of many
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reasons we already are familiar with, like preventing nausea.
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It doesn't interrupt signal transmission during interoperative neuromonitoring.
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And in my experience, there's not the same kind of stage two as with volatile anesthetics.
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So exubating on propofol usually means less coughing, bucking, salivating.
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It's just a smoother process.
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So if there's any concern about abdominal surgery or surgery to the neck or throat or
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face that you don't want to disrupt, propofol can smooth that out.
10:03
Well I think a lot of us do propofol wakeups where we're...
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And I did one yesterday actually where we turned off the gas a little bit early and
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then transitioned to propofol as we were waking up.
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That's a common technique that we all like to use.
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But you're advocating for using propofol for the whole thing.
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Is that right?
10:24
Yeah.
10:25
No gas.
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Really.
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From the get-go.
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So what's so bad about the gas?
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Well, there's a big focus on global warming right now.
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We're really starting to see a lot of the negative impacts of rising global temperatures.
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News agencies like the BBC are headlining our warming world as directly tied to atypical
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events like Hurricane Barrel making landfall earlier in the season than any other category
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five hurricane in the last 100 years.
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So people are taking climate change seriously.
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And so we're starting to look at ways where our anesthesia practice contributes to that.
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And one of the first areas that was identified is the use of fluorinated gases, which are
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our main anesthetic agents, the volatiles.
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So those contribute to global warming.
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Yes, they do.
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So we have news from the National Academy of Medicine.
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It acknowledges that the US healthcare sector accounts for about 8.5% of US carbon emissions,
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with hospital care accounting for about a third of that.
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So admittedly, anesthesia providers are not going to turn the tide on climate change,
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even if we all acted in concert over what is about less than 3% of US emissions, which
11:50
is not even global emissions.
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But in 2010, the American Society of Anesthesiologists started taking this issue seriously to the
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point that they authored a document on environmental sustainability in anesthesia practice by that
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title.
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The 2023 updates state that life cycle greenhouse emissions from inhaled anesthetics are several
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orders of magnitude greater than for that of propofol.
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And their number one strategy for mitigating the effects of inhaled anesthetics is to avoid
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their use in favor of intravenous and regional techniques.
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So why don't we currently just use propofol for all of our anesthetics?
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Maybe you could describe for some of our student listeners why we don't use propofol for everything
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all the time anyway.
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Well, in theory, you could.
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I think there's a long standing history, especially as a student, of just being trained on all
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the tools and stocks, which is absolutely appropriate.
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There's a cost difference, for sure.
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We can get into that in finer detail.
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But a propofol anesthetic is one of the more costly ones.
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And the gases just came onto the market prior.
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I think going back to the late 1800s, nitrous oxide was isolated and then the fluorinated
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agents came around in the 70s and early 80s.
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I don't know exactly when propofol was synthesized, but the others and the technique of using
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an inhaled, even going back to chloroform, or ether, those things are breathed.
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So I think that's just been sort of the custom of anesthesia.
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And we haven't yet really found a good reason to move away from it, especially given the
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cost.
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So here we are at a moment of considering, is it worth it to do so?
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Well there's different kinds of costs, I guess.
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We have the cost to the hospital is the cost that I think a lot of people think of, and
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it's more expensive to run to Tiva.
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That's sometimes a hard pill to swallow.
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But over time, there's the cost to the backyard barbecue, right?
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Of course.
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And that's really what we're working to try to preserve is our ability to hang out in
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the backyard, maybe not with Neil Young, but just generally speaking, right?
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So it makes sense to try to preserve that for our kids and for our kids' kids, right?
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Absolutely.
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Yeah.
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And there are lots of aspects to consider, like the life cycle analysis of any drug,
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which includes the packaging and how it's produced and how it's transported.
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So it's not just the global warming potential of the liquid itself that you're either turning
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into a gas or delivering directly intravenously.
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There's a bigger picture that surrounds it for sure.
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And the ASA has taken that into consideration in their recommendations.
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So is the ASA pushing for more propofol-based anesthetics, then?
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They are.
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Yeah.
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So one of the top two strategies are to use intravenous anesthetics wherever possible
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and regional, I think, actually is truly the way forward, the best bang for the buck in
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terms of patient and environment.
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So we can discuss that further too.
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But yeah, yeah, there's definitely a trend away from volatile anesthetics.
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I just don't think that information is really making headlines in the clinical setting.
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I first heard about it at a conference in Portland maybe five years ago.
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I saw PowerPoint by anesthesiologist Dr. Cheesebroke who practices in Oregon.
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He quoted the Lorax.
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It was fantastic.
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I know.
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It was like meticulously done research and also a lot of heart.
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That makes sense.
15:59
So you mentioned atmospheric lifetime of anesthetics.
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Can you tell me a little bit more about what that means?
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Sure.
16:07
Okay.
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So before we address that explicitly, let's go back a little bit and talk about global
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warming potential.
16:14
Sure.
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And then subsets thereof.
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So all anesthetic gases have a global warming potential because they're greenhouse gases.
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And those specifically are the gases isoflurane, desipo, and then nitrous.
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So the EPA recognizes greenhouse gases as those that trap heat energy within the Earth's
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atmosphere rather than allowing it to diffuse into space.
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Okay.
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Fluorinated gases are typically produced in smaller quantities than other greenhouse gases,
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but they're particularly potent and have orders of magnitude more global warming potential
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than for example, carbon dioxide.
16:54
Oh, okay.
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Global warming potential is a means of standardizing the environmental impact of greenhouse gases
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despite their unique properties so that they can be compared.
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So global warming potential is measured in CO2 equivalents, which considers a greenhouse
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gases radiative efficacy, which is the heat insulation value of the gas and the lifetime
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in the atmosphere.
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So it's duration measured out to about a hundred years.
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So when we talk about the environmental impact of greenhouse gas of any kind, we use metric
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tons of CO2, even if the gas is nitrous or isoflurane, and it contains those two components
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of heat insulation and duration in the atmosphere.
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Okay.
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So what are we talking about?
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How bad are our halogenated agents?
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Well, isoflurane has an atmospheric lifetime of 1.2 years.
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Is that a long time?
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Comparatively no, actually.
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Doesflurane lasts three years.
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Okay.
17:54
Doesflurane lasts 10.
17:55
Oh, okay.
17:56
So the decade long atmospheric lifetime of doesflurane being three to six times that
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of iso orcebo has garnered a lot of negative attention and has actually prompted the phase
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out of many hospitals in the last few years.
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Yeah.
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Our institution stopped using doesflurane a while ago, actually.
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Yeah.
18:15
Same with the hospital that I was working at before I came here.
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I remember actually conversations around it being phased out and whether or not we wanted
18:22
to keep like a vaporizer or two of it for special cases.
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And we did for a while.
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And I'm not sure if that was the case now that it's gone or if it's still there.
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But yeah, for the most part, it's been removed.
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That makes sense.
18:38
Do you feel like the reason it was removed was from an environmental standpoint or from
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a hospital cost basis standpoint or a mixture of both?
18:50
Do you know the cost comparison?
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Is does more expensive?
18:53
Well, I think it depends on the rate of flow.
18:57
I went to a doesflurane dinner once when I was a resident and they were trying to sell
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our hospital doesflurane.
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Okay.
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And I went because I was very poor at the time and a free steak dinner sounded like
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a good option for me.
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Yeah, right on.
19:14
And so I remember them talking about doesflurane being cheaper as long as you turn the flows
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way, way, way down.
19:22
But I think in general, it's more expensive.
19:24
Okay.
19:25
Well, I don't know about the costs specifically.
19:30
I asked our pharmacy here for example, like literal digit value costs on drugs, which
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we can get into in a little bit.
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But I did not ask about doesflurane specifically because we haven't been using it.
19:42
Yeah, that makes sense.
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But I know there are some other side effects regarding respiratory issues with wake up.
19:51
Right.
19:52
People tend to cough a lot more from it.
19:54
Yeah.
19:55
It's great for a quicker onset offset.
20:00
Or at least that's my familiarity with it was using it for bariatric surgeries.
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That was the last room where the vaporizer was kept when we were in the process of phasing
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it out.
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That makes sense.
20:12
Yeah.
20:13
But even there now I think it's pretty much gone because any skilled anesthesia provider
20:18
can type regas down the end of the case for a timely wake up.
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Just turn up your flows.
20:22
Exactly.
20:23
Okay.
20:24
So let's talk about the different costs that you were mentioning then.
20:32
What are some of the different costs of the different medicines that you were able to
20:35
find?
20:36
So here's a simple cost comparison in dollars among a handful of our common anesthetic agents.
20:43
Okay.
20:44
Robofol costs about a dollar per milliliter.
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The small 20 milliliter bottle is 20 bucks.
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The big 100 ml bottle is about 100.
20:52
250 ml bottle of SIBO costs about $385.
20:57
A 30 milliliter bottle of quarter percent bupivacaine is $13.20.
21:04
And the 2 milliliter bottle of 0.75 heavy marcane used for spinals is $9.30.
21:11
Wow.
21:12
Yeah.
21:13
Our regional team would be thrilled to make this point for us.
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I know.
21:18
One of my professors in grad school had this great quote, needle in the back is best.
21:26
I think it hasn't been challenged yet, at least not by these numbers.
21:32
So if we had $10 to spend on an anesthetic, let's see how far we could get with regional
21:40
versus propofol versus a volatile technique.
21:43
Because it can be a little complex to get your head around all this without a pen and
21:46
paper in front of you.
21:47
And so if you're listening in the car, we'll make it a little more graspable.
21:55
So let's start with the most direct drugs.
21:58
The bupivacaine and the marcane.
22:00
These drugs are super cheap on the order of roughly $10 to do a spinal that lasts a solid
22:05
2 hours or a regional block that could last 8 to 12 hours.
22:09
$10 for that.
22:11
Plus the cost of needles and maybe an ultrasound for the block.
22:15
Propofol is a little harder to quantify, but here's an easy way to think about it.
22:19
We often work with propofol in micrograms.
22:22
It's a standard 1% solution.
22:24
So it's always 10,000 mikes per 1 ml of propofol.
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And we can work with a 100 kilo patient just for easy math.
22:34
If we run a 100 kilo patient at 100 mikes per K per minute, we're using 10,000 mikes
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per minute.
22:42
So we're using 1 ml per minute.
22:46
So that's a cost of $1 per minute.
22:49
Okay, that's pretty easy.
22:51
So if we have that same 10 bucks to spend as we did for our regional patient, we get
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10 minutes of propofol anesthesia for the same price.
23:00
Gotcha.
23:01
Doesn't go nearly as far.
23:03
That's true.
23:04
Yeah.
23:05
Volatile anesthetics are easy enough to quantify in dollars, but the math will take you back
23:09
to your freshman chem notes on Avogadro's number.
23:11
So let's just look at the results of some research here.
23:15
In observational retrospective studies by French researchers published earlier this
23:19
year in Anesthesia, which is the journal of the ASA, which is sorry, the Association of
23:26
Anesthetists and that's comparable to the ASA here, but it's the Association of Practitioners
23:33
in Great Britain and Ireland.
23:35
Okay.
23:36
They compared the cost of TIVA with a mixed TIVA plus gas anesthetic.
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The approach was over roughly 47,000 anesthetics, 25,000 TIVA and 22,000 TIVA plus gas.
23:55
The mean length of each case was about two hours and the cost in US dollars for the TIVA
24:00
plus volatile anesthetic approach was 61 cents.
24:04
Oh, okay.
24:05
So that's incorporating gas into the mix compared to $12.38 for a pure TIVA strategy.
24:15
These costs are for the whole case, roughly two hours.
24:18
So going back to having $10 to spend on an anesthetic, you could more or less buy a TIVA
24:22
plus gas approach that would cover the whole case for 10 bucks.
24:26
And this study reports that the carbon footprint for TIVA, for the TIVA only strategy is 20
24:33
times less than that of the TIVA plus the volatile.
24:38
So it seems like from an environmental standpoint, it might make sense over time to approach
24:45
the legislature with some concepts about how we could maybe be subsidized or something
24:52
like that.
24:53
Yeah.
24:54
Gas is so cheap, but there's a huge savings in carbon emissions for TIVA at a higher cost
25:01
in dollars.
25:02
So it's really a matter of what feels most worth it.
25:07
Right.
25:08
That makes sense.
25:09
So dust foreign isn't the only anesthetic that's being phased out.
25:13
We're also sort of working to phase nitrous oxide out.
25:17
Is that right?
25:18
Mm-hmm.
25:19
Yeah.
25:20
So how has that been taking effect in hospitals across the United States?
25:27
The idea of getting rid of dust foreign and nitrous oxide, what does that look like?
25:33
Well, I'm not sure how it filters down through leadership, like where the idea gets planted
25:39
that eventually results in a change like in the OR.
25:48
But it seems like the general strategy is that because the overall contribution of anesthesia
25:55
to the problem of global warming is pretty small, it's not like we need to get rid of
26:01
these drugs 100% entirely, wash our hands of them, and never look back.
26:05
It's like we recognize the cases where nitrous oxide, for example, is actually the best thing
26:13
we can do.
26:15
Maybe for labor analgesia, you can take a couple breaths of the gas.
26:21
It's totally patient controlled.
26:22
There's very little risk to mom and baby.
26:25
And it's the only drug that has that property, really.
26:28
You can't just bolus a pregnant woman with 20 milligrams of propofol and wait for it
26:34
to wear off while she has a contraction.
26:36
That's not really a wise move.
26:37
Less than ideal.
26:38
Yeah.
26:39
So there are special use cases where nitrous oxide is actually the best thing for the job.
26:46
I think our friends at Children's would also probably reluctantly remove nitrous from their
26:51
armamentarium.
26:52
Right.
26:53
So because it's not a make or break, we're not utilizing tons and tons of concrete or
27:00
some other CO2 heavy industry.
27:03
We're using a tank of nitrous.
27:06
It makes perfect sense to keep it for these ideal cases and to phase it out of standard
27:12
everyday practice like a general anesthetic for an appendectomy.
27:15
We don't really need it.
27:17
We used it kind of like water when I was in school 11 years ago.
27:21
But in light of the fact that it has environmental repercussions that are pretty significant
27:27
and that there are really alternatives that don't compromise the practice in any meaningful
27:34
way, at least in my book, maybe some people got really attached to it and they're sad
27:39
to see it go.
27:40
But it hasn't really been a part of my practice since I learned how to use it.
27:46
So it's changed in both of our practices at different institutions.
27:49
But what about overall in the United States or maybe worldwide?
27:53
How have emissions from anesthetic gases changed over the years?
27:57
So here's a snapshot of how things have unfolded since about 1990 and where we are now.
28:03
The US EPA keeps an inventory of greenhouse gas emissions and sinks.
28:08
It's a report that contains a chart on fluorinated gas emissions from 1990 to 2022.
28:15
It's a simple line graph and it shows how fluorinated gas emissions peaked in the US
28:19
in the late 1990s and then declined significantly over the next three years, reaching a low
28:25
in 2002.
28:27
Since that later, fluorinated gas emissions have risen steadily to surpass late 90s levels.
28:33
And the upward trajectory continues through 2022.
28:38
I don't have more recent data than that.
28:40
But as of 2022, we were not gaining ground and we had been losing it steadily for nearly
28:47
two decades.
28:49
So the phase out of the most impactful greenhouse gases is one of anesthesia leadership's moves
28:54
to lessen the environmental impact of our practice within this metric of fluorinated
28:58
gas emissions.
29:01
So not all of us are in the room when these policies are being made or not necessarily
29:06
in the position to eliminate these things from our hospitals.
29:11
What can we do as individual anesthesia providers or as OR managers to help reduce the environmental
29:17
impact of anesthesia?
29:18
Sure.
29:19
There are plenty of things that pass directly through our hands that we can control every
29:23
case we do.
29:26
Certainly increasing awareness among stakeholders.
29:28
So all of us who practice anesthesia, OR managers, hospital administrators, raising awareness
29:34
on the harmful environmental effects of certain anesthetics and providing knowledge about
29:39
environmentally friendly alternatives is probably the first step.
29:42
But in terms of specific suggestions, the American Society of Anesthesiologists suggests
29:50
these ways to reduce inhaled anesthetic atmospheric waste.
29:55
Everyone use low flows, which I think we're all pretty familiar with that.
30:01
But what exactly does low flow mean to you?
30:04
I can dial things down to maybe like 0.8 liters per minute without the vent alarming that
30:11
there's not enough gas moving through the system, more compromising the patient's oxygenation.
30:20
I don't know.
30:21
They don't set a particular threshold for low flow.
30:24
Well, Alex Topala in our department did a grand rounds a while back.
30:29
I think it was before you joined us about using low flow silaflurane as more standard
30:36
practice not just to save, not just because of the environmental impact, but also to save
30:42
our department money.
30:43
The standard I think that a lot of people were doing here was one liter per minute of
30:49
oxygen and one liter per minute of air, just in the background because those are nice round
30:54
numbers and we as humans enjoy seeing nice round numbers.
30:58
I have seen anesthesia providers on the machines with two decimal points spend a lot of time
31:05
making it 1.00 as we're all sort of control freaks in anesthesia.
31:12
But what Alex's point was, and I agree with him, is that's probably too much, especially
31:18
if you're in a long case.
31:20
You can just turn down those flows and what he advocated for and what our theoretical
31:26
department standard, although nobody's going around policing this, is we turn everything
31:31
down to 0.5 of air and 0.5 of oxygen just as a way to cut down on the amount of SIWA
31:39
that we're using.
31:40
Sure.
31:41
So one liter total.
31:42
One liter flows.
31:43
Perfect.
31:44
Just sort of as a round number too.
31:45
Yeah, there we go.
31:46
So we're still satisfied that innate urge that we have to make it 1.
31:53
Fantastic.
31:54
Okay, so recommendation one, utilize low fresh gas flows.
32:00
The second recommendation is to avoid high impact inhaled anesthetics, so Des and Nitrous,
32:07
and we're kind of already on board with the phase out of those things.
32:11
Consider intravenous and regional techniques.
32:14
That's what we've been talking about for a few minutes here.
32:17
I feel like my observation of the bigger picture of anesthetic planning here includes quite
32:26
a lot of regional anesthesia, various techniques for blocking parts of the trunk, various limbs,
32:33
and then of course, like, spinals and epidurals when appropriate.
32:38
So yeah, like I mentioned earlier, I think the regional techniques are the cost-wise
32:45
least effective.
32:48
And for the patient, often provide some post-op analgesia as well.
32:54
So there's a fair amount of stretch that you get with that beyond the operating room itself.
33:00
So propofol has some advantages and disadvantages when compared to the gases.
33:07
The biggest disadvantage that normally comes to my mind when I'm thinking about propofol
33:11
is the risk of intraoperative awareness.
33:15
I wonder if you could speak a little bit on the risk of that just generally, and then
33:22
what our approach can be to mitigate that.
33:25
And then we can talk about some of the advantages of propofol.
33:28
Sure.
33:29
I was taught and have practiced for a decade with volatiles, assuming that 0.8% exhaled
33:43
sieve efflurane is the threshold for awareness.
33:47
So if you're running your anesthetic higher than 0.8, the risk of awareness is very low.
33:53
Banishingly small.
33:54
Yeah, especially if you've given a benzodiazepine like Versed prior to the start of the case.
34:00
I don't know of a specific metric like that for propofol.
34:06
Well the risk is slightly higher with propofol, of course.
34:10
But it's just something that we can keep in mind and again try to mitigate with some of
34:16
those same strategies, right?
34:17
Sure.
34:18
I mean, I think the most probably reassuring would be to put on a BIS monitor.
34:24
That gives you at least a number that you can watch drift.
34:29
But I've run propofol without a BIS for most of my career and have just watched vital signs.
34:39
And if I'm running somebody at about 100 mpg per minute and their blood pressure and heart
34:44
rate are aligned with their baseline for comfort, and I've given additional agents like some
34:54
sort of narcotic benzodiazepine, maybe some Presodex, I've felt pretty confident at that.
35:06
Yeah, that makes sense.
35:08
I think as long as you keep in mind just in general that it has a slightly higher risk
35:16
of awareness and you need to do things to mitigate that, especially in patients that
35:21
have a higher MAC value at baseline.
35:24
Maybe they're 21 years old and they smoke a lot of weed or something like that.
35:31
Yeah, and it depends.
35:32
Did they smoke that day or not?
35:34
Because one way our job is easier and one way it's harder.
35:36
Yeah, that's true.
35:37
But no, titrating in something like ketamine can be really helpful too, especially if you
35:44
pre-medicate with Versed, although ketamine doesn't necessarily require a benzodiazepine
35:50
to prevent delirium.
35:51
That's true.
35:52
Depending on the dose.
35:53
But there are therapeutic things happening in ketamine clinics without benzopremets that
35:57
are pretty promising.
35:58
So I don't know, maybe we're helping out mental health situations there too.
36:02
Yeah, sure.
36:03
Okay, so that's probably the main disadvantage that I think of.
36:06
What are some of the advantages of using propofol over the inhaled anesthetics?
36:12
Propofol is a very short-acting IV anesthetic that undergoes rapid hepatic metabolism and
36:17
renal elimination.
36:19
So only a small fraction of the drug is metabolized via extra hepatic routes, which means the
36:25
environmental impact is minimal.
36:29
But in terms of patient physiology and safety, propofol's hepatic metabolism plays a key
36:34
role in emergence, especially if you're looking to extubate the patient deep or to avoid emerging
36:39
through stage two, as with a volatile anesthetic.
36:43
In my experience, propofol wakeups don't involve near as much gudel manifestations
36:49
of tearing, salivating, delirium.
36:53
And once the tube is out, any remaining propofol continues to clear the body with little dependence
36:59
on ventilation.
37:01
So the volatile anesthetic, you get to a particular expiratory concentration where you can pull
37:05
the tube, whether that be deep or fully emerged, but the patient literally has to breathe off
37:11
any remaining volatile.
37:12
So there's a greater risk of hypoventilation, slowing the volatile agent clearance, and
37:18
potentially prolonging wakeup, or maybe even putting the patient back to sleep, depending
37:23
upon how hypopneic they are.
37:28
We can watch what we're doing and safely wake up a patient from a volatile anesthetic,
37:34
just as well as a propofol anesthetic, or an anesthetic combined from any other drugs.
37:40
It's not that a volatile anesthetic wakeup is inherently some kind of risk.
37:45
But I do think propofol offers an advantage at wakeup, because the metabolic pathway allows
37:50
the anesthesia provider a fairly predictable continued regression of anesthesia, because
37:57
it's not ventilation dependent.
37:59
Yeah, that makes a lot of sense.
38:01
Need to give more opiates impact you.
38:05
And you used a volatile anesthetic and they hypoventilate, there's maybe more of a risk
38:12
of sleepiness.
38:15
Whereas with propofol, the body is just going to continue to metabolize it, and they can
38:20
hold their breath and it will still be gone.
38:24
Hopefully they don't.
38:25
Hopefully they don't.
38:26
No, no, we don't want that.
38:27
You know, theoretically, it would clear at the same rate regardless of ventilation.
38:32
So I think what most of us are used to using propofol in is neurosurgery.
38:39
Tell us more about why we tend to use propofol during neurosurgery.
38:44
So I've got a bunch of research here.
38:47
Actually it's one study really, but we'll put that in the show notes.
38:52
Sure.
38:53
Great.
38:54
So, propofol is better for clearheaded awakening and preventing nausea and vomiting.
39:01
Propofol helps relax the brain and lowers pressure inside the skull.
39:06
It reduces the brain's oxygen use and decreases blood flow, unlike inhalation anesthetics.
39:12
So it doesn't significantly alter cerebral auto-regulation.
39:18
That makes sense.
39:19
So I can already imagine somebody thinking about changing their anesthetic plan to incorporate
39:25
Ativa, and they're thinking to themselves about all of the plastic that they're using
39:31
as they unpack all the syringes and all the pump tubing and everything else that goes
39:36
along with it.
39:37
So is it really that much more environmentally beneficial despite all of the extra plastic
39:43
that we're generating?
39:45
That's a really hard call to make and a really important point.
39:49
Propofol, yeah, undeniably uses a lot of plastic tubing to deliver the drugs via IV.
39:55
And when the plastics break down, they do so into particles so small that they can be
39:59
inhaled or ingested.
40:02
And tissue translocation is the big issue with particles that small because if they
40:05
can cross biological barriers like the lungs and the intestines, they can become lodged
40:09
in human tissues and have potential impacts like oxidative stress and inflammation, which
40:16
can disrupt the normal function of numerous body systems.
40:21
So in March of this year, the Mayo Clinic Individualized Medicine website headlined
40:24
research published by the New England Journal of Medicine on the presence of micro and nanoplastics
40:31
in human blood vessel plaques and speculated at a link to increased risks of stroke, heart
40:38
attack and death.
40:40
So we're going to do great with greenhouse gases and global warming, but then we're all
40:45
going to just be made of plastic at the end of the day.
40:48
Yeah, all the tubing matters.
40:51
And at UC we have two choices regarding the pumps we use to deliver propofol.
40:56
One pump uses tubing and plastic chambers that require 20 milliliters of liquid just
41:00
to prime it.
41:01
And the other requires that the propofol be drawn out of a glass bottle into a 60 ml syringe,
41:07
but involves far less tuning.
41:09
So which of those is the better choice?
41:12
I'm not sure that there's a way to quantify that.
41:15
At least not without a lot of like modeling and math and lifecycle analysis that's maybe
41:21
a heavier lift than what we want to do right now.
41:23
That's fair.
41:24
Yeah, but the point is there that nothing is without risk and nothing is the clear advantage.
41:31
Maybe we do reduce greenhouse gas emissions, but what we contribute to plastic wastes and
41:39
the environmental impact there is potentially just as considerable.
41:43
So in a lot of these procedures that we're doing, we generate a decent amount of propofol
41:49
waste.
41:50
I'm thinking of all the times that I've drawn up a second stick of propofol and ended up
41:55
not using it.
41:56
What tips do you have for minimizing the propofol waste that we have during our procedures?
42:01
Yeah, I mean, it's nice to look at the screen on the ventilator and see or on your monitor
42:09
and see what your end title is.
42:13
It's nice to be able to look at the screen on the monitor and see what your end title
42:17
SIBO or DEZ or nitrous or whatever exhales.
42:21
That's true.
42:22
Because it gives you a benchmark for how much you need.
42:27
And we know if we watch patient responsiveness, we can titrate the mics per kick per minute,
42:33
but we don't quite know how much to put in the syringe.
42:37
So there's simple math.
42:39
Anytime you're running 10,000 mics per kilo per minute, you're running one ounce per minute.
42:49
So that's a 100 kilo patient at 100 mics per kilo per minute.
42:55
If you have a smaller patient about 70 kilos and you're running them at approximately 75
43:02
mics per kilo per minute, that's 5,000, so half of that.
43:08
And we talked earlier about anytime you're getting to 10,000 mics per kilo per minute,
43:12
that's one ml per minute.
43:15
So if you're drawing up a bottle of 20, that's a 20 minute bottle for a 100 kilo patient
43:20
at 100 mics per kilo per minute.
43:22
If you're taking that same 20 ml bottle and running it at 75 for a 70 kilo patient, then
43:31
it's going to last twice as long.
43:33
So that's a 40 minute bottle.
43:34
So how do we predict how much time the surgeon is going to take?
43:37
This is where you get your magic.
43:40
You start shaking and then you just wait for the little triangle to float to the top that
43:45
says ask again later.
43:47
So zooming out, let's talk about making anesthesia more environmentally friendly.
43:54
What trends do you see happening?
43:56
Where do you see things going in the future?
43:58
Yeah.
43:59
So this is kind of an interesting story that I heard about on NPR the other day in terms
44:06
of using regional techniques, even without propofol, this case in particular, at least
44:14
as far as I can understand the details.
44:16
The patient was responsive to name throughout the whole case and maybe got some sedation
44:23
versus fentanyl, ketamine, something maybe, but was able to respond to name at major points
44:29
during the surgery.
44:30
So the story is that in June of 2024, the surgeons at Northwestern Medicine in Chicago
44:36
performed the first known awake kidney transplant, awake, in the United States on a 28 year old
44:44
named John Nicholas.
44:46
Nicholas received a spinal and some light sedation.
44:50
ABC7 Chicago reported that the patient was responsive to name during the surgery and
44:55
happy to receive updates on milestones throughout the process.
44:59
They also report that Northwestern Medicine is looking into establishing an awake program
45:04
or accelerated surgery without general anesthesia in kidney transplants for patients who want
45:10
the option and hope to limit the admission to a 24 hour stay.
45:16
This is totally outstanding and in many ways an ideal case to substitute for GA.
45:22
But this is a great moment to champion regional anesthesia of all kinds also, not just norexial,
45:28
infusion catheters, single shot blocks, field blocks, yes, any of it.
45:32
Anytime you can numb the surgical area, there's so much potential to reduce if not eliminate
45:36
the need for other kinds of anesthesia.
45:39
You can easily cut the mac of an inhaled anesthetic by half by using an inner scaling infusion
45:43
catheter for a total shoulder and provide three days of post-op analgesia all in one
45:47
go.
45:48
So I think regional is the way forward, especially with the cost comparison that we did earlier
45:53
in dollars.
45:54
Regional anesthetics, the little bottle of local anesthetic is far less expensive than
46:00
any of the other options.
46:03
So maybe gas.
46:04
That's 61 cents is hard to keep.
46:07
So I think you've provided us with an excellent overview of all the things that we can do
46:13
to keep anesthesia more environmentally friendly.
46:16
Using propofol is probably better than using the gases in general.
46:20
There's some better side effect profiles that go along with that.
46:24
Regional is maybe the most cost effective thing that we can do.
46:27
And then I think we just have to keep in mind the amount of plastics that we're using when
46:31
we're unpacking everything.
46:33
I think these are all awesome points.
46:35
So let's talk about what style points have brought you success in your career in and
46:41
out of the operating room.
46:42
Can you give us some of your ideas for how you like to run things?
46:48
Sure.
46:49
I think that's just an ongoing questioning of often just the small ways where I can do
47:00
something a little better.
47:03
I went on a medical mission trip to Bolivia in 2014 and we had, I don't know, like three
47:09
syringes per patient.
47:11
And this was a year after I graduated from my master's degree.
47:16
And we were basically told that syringes are single use.
47:23
And I think for a lot of people that's the case.
47:26
But we were in an environment where resources were limited and to reuse a syringe, if you
47:34
think about it, is actually a fine thing to do.
47:37
If you're worried about drug cross contamination, maybe, I don't even know what two drugs would
47:43
precipitate.
47:44
But just for example, if you gave fentanyl and that's all finished and then you need
47:48
to give Zofran at the end of the case, you do have to be conscious about your labeling.
47:54
It's important not to get yourself mixed up, but you could take that same 3cc or 5cc syringe,
48:01
you could flush it with the IV tubing that you're using to give the patient all of the
48:06
drugs anyway, and then draw up a single vial of Zofran and give that.
48:11
So you just saved yourself a 3cc syringe worth of plastic that's ultimately going to go on
48:17
the landfill.
48:18
I mean, if we all did that once a day, every day, the pile would be huge.
48:23
So that's something.
48:29
But here we are talking too.
48:32
I don't know, we met just a couple months ago and a conversation led us to this opportunity
48:37
to have a bigger conversation that more people can hear so we can share ideas.
48:44
And it makes me think, I wonder if our NSAs are getting this information.
48:50
I wonder if they're going to listen to this podcast because they're the ones who are in
48:54
the role right now of developing their techniques, figuring out their ways.
48:58
So maybe this will loop back to students out there who are considering how they want to
49:05
best do their job.
49:06
So just finding all the different ways that opportunity just arise and connect and grow.
49:14
Thank you so much for joining us.
49:15
I really enjoyed having you on the podcast.
49:18
Thank you.
49:19
I'm so glad to be here.
49:20
Thanks again for joining us today.
49:23
If you have your own ideas about how we can perform safe, sustainable anesthesia, please
49:27
feel free to drop me a line at stylepointspodcast at gmail.com.
49:32
And don't forget to share this with your friends.
49:34
Take a deep breath, open your eyes, we're all done.