February 12, 2025 • 45 mins
Exploring Methoxyfluorane for Wilderness Pain Management with Dr. Ross Hofmeyr
In this episode of Wilderness Medicine Updates, host Dr. Patrick Fink discusses the use of methoxyfluorane, an anesthetic gas for pain management in wilderness settings. Joined by guest Dr. Ross Hofmeyr, an anesthesiologist and wilderness medicine expert from South Africa, the episode delves into the history, usage, benefits, and limitations of methoxyfluorane. Highlighting its efficacy, ease of use, and safety, especially for pre-hospital scenarios, Dr. Hofmeyr shares insights into its ideal applications, contraindications, and personal experiences. The episode underscores the significance of methoxyfluorane as a potent analgesic suitable for acute traumatic pain and procedural analgesia in austere environments.
Links
Methoxyflurane at Altitude - Case Report
Methoxyflurane in the Outback - Survivor Clip
WMS Pain Management Guidelines
Chapters:
00:00 Welcome to Wilderness Medicine Updates
00:55 Meet Dr. Ross Hofmeyr
03:14 Dr. Hoffmeier's Background in Wilderness Medicine
04:45 Methoxyfluorine: An Overview
12:20 The Mechanics of Methoxyfluorine Inhaler
20:15 Practical Applications in Pre-Hospital Pain Control
20:53 Analgesic Intervention: Quick and Effective
21:09 Using Methoxyfluorane in Wilderness Settings
22:42 Training Non-Medical Personnel
23:49 Procedural Analgo-Sedation
24:30 Regulatory Considerations and Prescriptions
26:33 Combining Methoxyfluorane with Other Medications
28:10 Monitoring and Safety
29:09 Ambulating Patients with Methoxyfluorane
31:31 Environmental Considerations: Temperature and Altitude
40:10 Cost and Practical Downsides
41:45 Conclusion and Final Thoughts
As always, thanks for listening to Wilderness Medicine Updates, hosted by Patrick Fink MD FAWM.
Connect with us by email at wildernessmedicineupdates@gmail.com.
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Ross Hofmeyr (00:00):
And there's this iconic image of this guy coming
(00:02):
across the river with thismassive green whistle in his
mouth.
You know, and the paramedicskind of holding him in his hands
as he, as he wades through.
And all of us in South Africawent, you are my brew.
Look at this.
They've got lack of, lack ofbongs there.
Hey.
And, and turned out it wasn'tmarijuana.
But it was, it was methoxy,Florin.
And that really sort of wentbing for many of us in the rest
of the world going, well, hangon a moment.
(00:23):
Why don't we have this?
We, we want this.
Patrick (00:26):
Hello, and welcome back to Wilderness Medicine Updates,
the show for providers at theedges.
I'm your host, Dr.
Patrick Fink, and I'm happy tobe talking today about
methoxyfluorine.
What is methoxyfluorine, youmight ask?
And if you ask that question,you probably live in the United
States.
(00:47):
Methoxyflurane is an anestheticgas that can be used to treat
pain in the wildernessenvironment.
It comes in a nifty littlepackage, and we're going to talk
a lot more about that, and I'msuper happy today to be joined
on the show by Dr.
Ross Hoffmeier.
Ross is an anesthesiologist wholives and works in an academic
(01:09):
setting in South Africa, but hehas a much more varied and
interesting wilderness practicethat goes well beyond the
confines of the hospital walls.
As you'll discover, Ross is awealth of information about
methoxyfluorane, its prior usein anesthesia, and its use now
in the wilderness and prehospital setting, both its
(01:30):
benefits as well as somedownsides and some settings
where it may or may not beterribly effective.
If you want to learn more aboutRoss, What this medication is,
how it's used, how it fits intohis pain management plan, ideal
settings for its use,contraindications, and most
importantly, what made him saythat in the cold open, I owe a
(01:53):
big thanks to Aaron and Eddie,two listeners who wrote in with
questions about methoxyfluraneafter our last episode on
ketamine.
I always love getting listenerquestions and there's more in
the inbox, some.
Conversations that have beenongoing that are going to bring
some interesting episodes to youguys.
So please continue to reach outas always wilderness medicine
(02:14):
updates at gmail.
com and I'll hit you with thatagain in the outro.
Without further ado, here is Dr.
Ross Hoffmeier.
Ross Hofmeyr (02:23):
Mozambique was fantastic.
We.
flew into the backside of atropical storm and into a
country undergoing civil unrestwith people thinking it was
going to be going into a civilwar.
And it was absolutely blissfuland peaceful.
Sea was a bit heavy some quitebig swells, but we got some
great diving done and the peoplewere fantastic and we had no
(02:43):
problems.
So it was really nice.
Patrick (02:46):
Great.
And now you're at the WildernessMedicine Society Conference in
Crested Butte.
Ross Hofmeyr (02:51):
That's right.
Yeah, I just wrapped up here inColorado.
If I look a little bit pink inthe face, it's because it's been
an absolute bluebird, sunshinyday here on the slopes and I've
just got in about 20, 000vertical feet of skiing in for
the day.
Patrick (03:06):
Fantastic.
It sounds like a toughlifestyle.
I know that your, your job byday is an anesthesiologist.
How do you describe the rest ofyour roles and how that
interacts with the world ofwilderness medicine?
Okay.
Okay.
Ross Hofmeyr (03:24):
as an anesthesiologist or anesthetist,
as you say.
I'm based at a universityhospital in Cape Town in South
Africa.
and we'll see first hearttransplant.
My day job there is as acardiothoracic anesthesiologist.
And I do a lot of airway stuffas well.
(03:45):
And so that's what pays thebills and brings home the bacon.
But wilderness medicine has beenmy passion for a very long time
after.
Growing up through search andrescue as a, as a student in
training and then as a juniordoctor I served as the
expedition leader and and doctorfor our South African research
team in Antarctica winter overthere.
And I've been involved inwilderness medicine and
(04:07):
wilderness rescue ever since.
And in the early noughtiesMountain Rescue colleague and I
started a small company, whichhas remained small called Wild
Medics.
We're based in Cape Town inSouth Africa, and we've been
providing wilderness medicalsupport and particularly over
the last number of years,wilderness medical training with
an African focus and flavor butobviously, you know, trying to
(04:31):
incorporate the, the bestinternational practices there as
well.
So, Wilderness medicine is my mymistress and my passion project.
And the anesthesia is my, my dayjob.
Patrick (04:41):
I'm glad that you're the person to come on and
discuss this topic on thepodcast.
because after the last podcaston ketamine hospital pain
control, I got a number ofquestions from listeners who
wanted to know more aboutmethoxyfluorine.
when we were putting togetherthe pain guideline, you were
kind of the gas anesthesia guybut methoxyfluorine is not
(05:03):
something familiar to me.
It's.
Not available in the UnitedStates outside of some ongoing
clinical trials.
So I wanted to begin sort of asthe I'll play the novice here
that I want to know what what ismethoxyfluorine?
Where where does this fit intothe world of pain control and
why have I never heard of it?
(05:24):
Silence.
Ross Hofmeyr (05:37):
a volatile anesthetic agent.
It's an old drug.
The first published clinicaltrials were in the late fifties,
early sixties.
It, so it's been around for avery long time.
It is fairly unique amongst theinhalational anesthetic agents
in that it also provides ananalgesic effect.
So most of our Inhaledanesthetic agents, particularly
(06:00):
fluorinated drugs the ones thateveryone's very familiar with
would be things like isoflurane,sivoflurane, desflurane, those
are the ones that are in modernuse.
joining us people probably willbe familiar with, and we'll
definitely talk about this a bitmore, of course, is nitrous
(06:22):
oxide.
And that's commonly been used asan analgesic agent when it's
mixed in a 50 50 concentrationmix with oxygen, and that's
known as oxen that's been usedfor labor analgesia.
It's been used in pre-hospitalanalgesia.
And, and, you know.
People are very familiar withthat concept of providing an
inhalational drug, which gives,it gives pain control.
So methoxy and nitrous oxidereally are the only anesthetic
(06:46):
inhaled agents we have that givethat analgesic property.
Now, an astute listener is goingto say, well, hang on a moment.
You can't actually anesthetizesomebody with nitrous oxide
because the, the, the Mac or theminimum alveolar concentration
of the gas, which you need tobreathe at sea level to render
somebody unconscious is around104%.
(07:06):
and somebody 104 percent of ananoxic show you've got larger
problems than anesthetizingthem.
You're just going to euthanizethem.
But the concept of givingsomeone a gas, which has got
analgesic properties, I think isfamiliar to us from, from
Entonox.
Now, methoxyfluorine is actuallyright at the other end of the
(07:27):
spectrum in terms of potency.
So provided only a long timeago.
When alveolar concentration,that's really the concentration
at sea level of that gas in abreathing mixture, which will
render 50 percent of, ofpatients or 50 percent of
subjects non responsive to asurgical stimulus.
(07:49):
So you give the person that muchgas and half of people won't
move or show any sign of asurgical incision.
Now we add other agents to tryand We work with those values
and we monitor depth ofanesthesia, et cetera and we're
familiar with our everydayvolatile agents, something like
Desflurane that a lot of peoplemay use the, the MAC value is
(08:09):
around 6%.
Sevaflurane is a little bit morepotent.
The MAC value of that is around.
Let's say 2 percent for ease ofdiscussion.
Isoflurane, even more potentaround 1.
2%.
And the MAC value ofmethoxyfluorane So, is 0.
16%.
So it's actually a very, verypotent anesthetic drug The
(08:29):
potency just in terms of the MACvalue is that ignores how much
of the, of the volatile agent isabsorbed and, and dissolved into
the bloodstream and particularlyabsorbed into the fat.
So that has got a lot of thethe, the lipid the has a lot to
do with the, the speed of onsetof the, of the different agents.
the so methoxyfluorine, althoughit's very, very potent.
(08:51):
Has actually, it's actually alittle bit of a slow agent to
anesthetize patients with.
So when it came into clinicalpractice, and now we're talking,
you know, 50s, 60s it was quitepopular because Because a lot of
the agent is becoming absorbedit then takes a very long time
to, to come back out of thesystem and that gives you a
really nice, long analgesictail.
(09:12):
So people would often mixvolatile agents and they would
use methoxy plus something elseto get the patient off to sleep,
turn the other agent off, runthe patient on methoxyfluorine,
and then at the end of theprocedure, they may take quite a
while to wake up, but they'vegot this beautiful analgesic
tail.
So that's really handy.
Okay.
(09:34):
And that's because it's nolonger in clinical use for
anesthesia.
The problem with using it as ananesthetic agent is that if you
use it at high concentrationsfor long durations, it has got a
to take nephrotoxic effect.
So it directly causes a ininjury.
In fact, I'm not quite thatsimple.
it in.
(09:54):
chemical byproducts, which causea, cause a kidney injury.
about we now know from the, fromthe literature, to is that that.
and I'm A clinical nephrotoxiceffect tends to emerge at around
five MAC hours worth of dosage.
So if you think of administeringone MAC to keep a patient asleep
for five hours, that's the kindof dose that you need to cause a
(10:15):
clinically evident nephrotoxicevent.
And biochemical nephrotoxicityis around 2.
5 Okay.
problem, of course, is that themoment that people started
seeing these renal injuriescoming out, there's a greater
risk if you've got underlyingrenal disease and very, very
(10:38):
rapidly, the Toxifluranedeveloped a bad rap and quite
quickly it was taken off themarket as an anesthetic agent.
So that's, that's where itdisappeared to.
It was, however, even at thattime in use as an analgesic
agent and it was being used in avery, very simple draw over
(10:58):
vaporizer.
So effectively, you think abouta tube with some wicking
material inside, you pour someof the liquid methoxyfluoride
inside, the wick helps to spreadit around, the gas then
vaporizes inside the inhaler,and you suck through it, and you
get a, you get an inhaled dose.
In fact, there was a, a devicewhich it was called the the
analgizer, be careful topronounce that correctly if you
(11:20):
read the packaging and it wasbeing used for for labor
analgesia and was also beingused for pre hospital analgesia.
And in fact, the, the typicallabor analgesic dose was up to
15 milliliters or 15 CC ofliquid methoxyfluorine into the
inhaler and all that number 15in your head, because Okay.
(12:05):
the full duration of the last 50or 60 years.
And there's extensive literatureand.
You have tens of thousands ofdocumented uses there as a pre
hospital analgesic, which makesit very attractive for the kind
of work that that you and I do.
Patrick (12:20):
So the current manifestation is a device which
contains some set amount ofmethoxy fluorine, which can be
used in the field, sort of likeprobably the best analogy to the
younger humans listening wouldbe something like a vaporizer
type device, right?
Like it quite literally has avaporizable liquid that sits on
(12:42):
a wick.
And as you breathe through it,it draws off some methoxy
fluorine.
But you're only achieving thelevel of the inhalational agent
that will deliver analgesia,right?
You can't possibly pull on thisthing hard enough to make
yourself pass out.
Am I correct?
Ross Hofmeyr (12:58):
You're mostly correct.
So in fact, the device itselfthat, that now on the market,
and it's sold in different areasof the world under slightly
different names.
Some, some places call itPenthrox, some call it Penthrop,
some call it Penthrane butpretty much the same thing.
And it now comes in a, in a biggreen plastic.
Tube that looks a lot like awhistle.
(13:18):
So some people talk about thegreen whistle.
Frankly, you know, a big greenthing that you suck on, which
makes you quite lightheaded andfeel a bit high is, as you say,
very easily approachable conceptto many people the younger
people and probably lots ofpeople here in Colorado but uh,
Patrick (13:34):
Okay.
Ross Hofmeyr (13:52):
on the device.
There were some concerns
Patrick (13:54):
I,
Ross Hofmeyr (13:55):
particularly the pre hospital community in
Australia that Becausemethoxyfluorine itself is
incredibly aromatic you, you cansmell the tiniest concentration
of it in the air around you.
Patrick (14:07):
of
Ross Hofmeyr (14:08):
about people who were sitting in the back of
ambulances with patients whowere breathing on these green
whistles that they might begetting a, an occupational
exposure,
Patrick (14:16):
much.
Ross Hofmeyr (14:17):
to methoxyfluorine.
And so the, the modern device isactually packaged with an, a
little activated charcoalabsorber.
That clips into the exhalationvalve.
So it's got a one way valve.
So when you, when you suck onit, it sucks through the device.
And when you blow on it, itblows out through an exhalation
valve.
And you can put this littleabsorber onto it.
And, and that then is supposedto capture a lot of the
(14:39):
methoxyphore in it, but go outinto the environment.
And it's It's worth that Imentioned the absorber device
because you can actually varythe dose that the patient is
receiving by getting them to, toclose the the air entrainment
hole that's on the absorber.
And if you take the absorber offcompletely, which for us in a
wilderness environment wherewe're out in the fresh air would
(15:00):
be entirely safe.
Then they actually get a muchlower dose of the methoxy
because it.
It entrains some air through theabsorber hole on, and we
actually documented this andquantified this in some work
that I did a few years ago atDuke University in their
altitude chamber.
Unfortunately, I can't send youto the publication of that work.
It's been presented at the WMS.
It was supported by a grant fromthe Wilderness Medical Society,
(15:24):
but we showed that actually youcan vary the dose quite
significantly by eitheroccluding the hole, adding the
absorber or, or leaving it open.
So you asked whether.
you can give somebody too muchwith with methoxyphorin inhaler?
And the short answer is that foran adult patient breathing
normal adult tidal volumes theanswer is no.
(15:44):
If you use the standard dosethat comes in the vial, it's a
three mil vial.
Remember we said earlier.
That for labor analgesia, theywere giving 15 milliliters.
So it's literally a fifth of thedose that was being used there.
That gives you around 0.
3 years, 0.
26 to 0.
29 Mac hours worth of doseexposure, and that's, that's
(16:06):
enough to make you feel a littlebit dizzy, maybe a bit
lightheaded, sometimes peoplecomplain of a bit of nausea or a
bit of headache but it'scertainly.
And the best, the bestexpression that someone said to
me is it makes me feel goofed.
You just feel a little bit dizzyand out of it.
But obviously it takes away alot of your, a lot of your pain.
For a normal size adultbreathing on the device, they're
not going to be able to get ananesthetic dose.
(16:27):
So that's really quite safe.
There is some concern andthere've been a number of papers
published where they've usedthis for pediatric analgo
sedation and pediatricprocedural sedation.
And in fact, If somebody isunable to breathe through their
mouth to breathe with thedevice, in fact, the outer
diameter of the inhaler itselffits perfectly into the inner
(16:52):
diameter of a normal medicalface mask, so your anesthetic
face mask, and so in some ofthose studies, they have They
put it into a face mask and heldthat for for children.
And there with a much smallertidal volume, actually, there is
a risk of approaching ananesthetic dose.
One of the effects ofmethoxyfluorine, of course, the
side effects is it causesdrowsiness.
(17:13):
Well, it's an anesthetic, sowe're not really surprised.
It's also quite a potentrespiratory depressant.
And so our.
Our common practice and ourcommon guidance is that it
should, in a non monitored orout of hospital setting, it
should be self administered by apatient.
So if they start to get a littlebit drowsy or their respiratory
rate starts to decrease, they'renaturally going to take it out,
(17:34):
drop it, or they're going toinhale less of it.
Rather than than holding it withwith a face mask.
So that's the, that's thecaveat.
It is not going to put you tosleep if you're using it as an
analgesic in an adult patient.
It's in most countries where itis currently available.
It's off label for pediatrics inany case.
But the proviso is don't attachit and breathe it through a
mask.
Patrick (17:56):
Much like nitrous oxide, we give the patient the
control over the mask here,you're having them hold the
whistle.
And so if they're dosingthemselves too heavily and
becoming goofed, as you said,they will no longer be able to
hold it to their mouth.
Yes.
Ross Hofmeyr (18:10):
Absolutely.
Patrick (18:11):
so just want to confirm my understanding.
You can modulate the dose byessentially controlling how much
air is co inspired with theanesthetic agent.
So if you were to the.
air intake, then all of the gaswhich is being inspired is
coming across themethoxyfluorine wick and get
your highest level of, yourhighest dose.
(18:34):
Allow the, allow that to be opento air, you get sort of a
moderate dose, and then if youtake the whole off, you're going
to entrain further more air andresult in a further lower dose,
is that correct?
This transcript
Ross Hofmeyr (18:46):
That's that's 100 percent correct.
So the highest doses, if youinclude the entrainment hole,
Patrick (18:51):
Dakota is
Ross Hofmeyr (18:52):
if you leave the entrainment hole open with the
scrubber on, you get a slightlylower dose.
And if you take the scrubberoff, you get the lowest dose.
And
Patrick (18:59):
award
Ross Hofmeyr (18:59):
it's so aromatic
Patrick (19:01):
Doctor of
Ross Hofmeyr (19:02):
who's practiced a little bit of anesthesia will
probably have experienced
Patrick (19:05):
Human
Ross Hofmeyr (19:06):
a gas induction for a child using something like
Sivaflurane.
If you put a mask on and youcrank that right up to a high
concentration and the firstbreath or two is really
concentrated volatile, peoplewill often find that quite
irritant.
They'll have a bit of a cough.
They might balk at that.
And it's quite similar for mewith Mesoxiflurane.
I often tell people.
To take their first one or twosmall breaths, keep the
(19:28):
entrainment hole open, get afeel for the taste and the smell
of the methoxyfluorine, see ifit's having an effect on their
pain.
And the onset of analgesia isactually quite rapid.
It's within you know,
Patrick (19:41):
Yeah.
Ross Hofmeyr (19:44):
getting used to that, if they're finding that
they want more analgesic effectto then close that hole and to
take nice, deep slow breathsthrough the inhaler.
Patrick (19:53):
Okay, so now I think that's a pretty good overview of
the nuts and bolts of theanesthetic background of
methoxyfluorine, as well as theactual mechanics of the inhaler.
And I'll put a link in the shownotes to pictures of both the
older green whistle and thenewer device that has come out.
(20:13):
Where does.
Methoxyfluorine fall into yourpractice for pre hospital pain
control?
Where does it fit in with oralanalgesics, IV, or, or stronger,
you know, narcotic typemedications?
In what settings are youchoosing to use it?
Ross Hofmeyr (20:29):
Okay.
That's a great question.
So the first thing to recognizeis that we're limited in the
dose that we can administer.
So we're giving about a threemil initial dose and depending
on how rapidly somebody isbreathing and, and you know,
whether they're occluding theholes in the So the breath
they're taking, that gives youabout 20 to 30 minutes worth of
analgesia.
And then we can repeat that doseonce if we're following the the
(20:52):
package insert.
So you're really looking at ananalgesic intervention, which is
it's immediately available.
It's very quick to prepare that,you know, the device can be
active within 20, 30 seconds, ifyou, if you're familiar with
using it and it's giving you,let's say 32.
To 60 minutes of analgesia thetwo main areas that I like to
(21:15):
use it in my practice are numberone Patients who particularly in
the wilderness setting have hada traumatic injury and they need
potent analgesia.
So it is a potent analgesic.
I wouldn't use it for you know,someone who's got a small
laceration that just needs a bitof care.
It's a potent analgesic.
It's immediately available to beadministered.
It doesn't require me to get outIV access.
(21:36):
It doesn't require me to openany vials.
I don't have to draw up anydrugs.
I don't have to check anyconcentrations.
It's very much.
Open the packaging, pour in themethoxy, give the patient a
brief instruction, and allowthem to start breathing.
And that then frees me up tocontinue with my other
interventions.
So it's a very good bridge toproviding IV analgesia, or
(21:59):
perhaps intramuscular analgesiaif you're dealing with less
severe pain, but as you wellknow, lots of considerations
around giving giving IM drugs.
It's excellent in giving youthat first 20 minutes while you
are completing your primary andmaybe secondary survey,
establishing IV access, and thenstarting to titrate in you know,
rapid acting or a more longeracting analgesic, whether that's
(22:23):
going to be something likeacetaminophen or it's going to
be stronger in opiate orketamine or other things.
So that's the first reallyuseful space is an analgesic
bridge.
You do need a conscious,cooperative patient, and they do
need to have moderate to severepain but it gives you that first
20 to 30 minutes.
Patrick (22:39):
Okay.
Ross Hofmeyr (22:42):
I'll say this with caution because obviously it
depends on the regulatoryenvironment where you're working
but we have trained a lot of ourwilderness first responders our
SAR personnel, and then we'vetrained some of our non
Patrick (22:54):
Okay.
Ross Hofmeyr (22:57):
medically trained tour guides and wilderness
guides and expedition leaderswho have got wilderness first
aid training, wilderness firstresponder training and are
working fairly independently inremote areas, we've trained many
of them to administermethoxyfluorane as an analgesic
agent.
We've got a very quick littlechecklist.
And so if I've got a team whoare doing a guided
(23:19):
investigation, Motorcycling tripthrough Cambodia somebody comes
off with a shoulder dislocationor a tibfib fracture and they're
in severe pain, then that teamcan immediately administer
methoxyphorin while they'restabilizing the patient,
splinting, et cetera, et cetera.
And often that gets you throughthat first really painful period
of of immobilization and soforth.
Patrick (23:39):
much.
Ross Hofmeyr (23:49):
More seldom, but it does definitely have some
efficacy and that is forprocedural analgoacidation.
If you're doing a painfulprocedure in a remote
environment and you've got very,very limited monitoring.
And Matt Wilkes has got a lovelycase report of using methoxy for
placement of a suprapubiccatheter at four and a half
thousand meters altitude, whereit was, it was used for exactly
(24:09):
that that purpose.
So and again, there's plenty ofpublications in adults and kids
of using methoxy for proceduralsedation.
So I think that's a reasonableindication, although I will say
again, the caveat depends onyour regulatory environment.
In South Africa, for instance,it's not actually licensed for
procedural sedation.
It's only licensed for acutetraumatic pain.
Patrick (24:31):
In places where it is available, let's stick with
South Africa because you're mostcomfortable with that.
Does it require a prescriptionto obtain it?
And how does one go aboutgetting a hold of
methoxyfluorine?
Ross Hofmeyr (24:42):
Yeah.
So in South Africa, it's a, it'sa prescription drug.
It's it's a schedule five out ofseven level scheduling.
So it's actually quite a highschedule drug.
That's because they didn'tchange the scheduling when it
came back from its, you know,anesthetic use.
That does require aprescription.
And so it's supposed to be usedon a named indication, named
(25:04):
patient basis.
The way that we get around thatfor our wilderness usage is that
we have a very defined protocol,and a non
Patrick (25:14):
by
Ross Hofmeyr (25:22):
this is a situation.
The patient's past thechecklist.
Can I go ahead and give them theFoxy?
And, and we then prescribe it aspart of a, of an expedition kit.
Much the same way that we do alot of our other prescription
medications that go into thosekits.
Patrick (25:34):
And in that kit or in your personal med kit that you
might either carry with yourecreationally or as a
responder, are you carrying justthe two vials of methoxyfluoride
or do you carry more?
Ross Hofmeyr (25:45):
Yeah, I carry an inhaler and well, the delivery
device and two vials becausethe, the likelihood of needing
more than one.
inhaler for one patient in mynormal practice is quite low.
I do obviously have access toother agents, so if I did have
another patient where I didn'thave IV access and I had acute
severe pain, I'd have options todo things like intranasal
(26:07):
ketamine or intranasal fentanylother things like that.
And those, those still remainreally, really good options.
I'm not advocating that, youknow, methoxy is better than
other drugs.
There's some, there's some goodliterature out there.
But certainly in terms of Theease of deliverability by less
trained personnel and the easeof freeing up your hands so you
(26:29):
can do other tasks,
Patrick (26:30):
CastingWords
Ross Hofmeyr (26:32):
there.
Patrick (26:33):
How do you feel about administering methoxyfluorine to
a patient who has alreadyreceived other centrally acting
medications?
you've, you've providedintramuscular fentanyl or
intranasal ketamine, and nowyou're approaching a painful
transition or splinting or whathave you, you want to consider
using methoxyfluorine forbreakthrough of that next level
(26:54):
of analogous sedation.
How do you feel about thecombination of those and how do
they play together?
Ross Hofmeyr (27:00):
So I think From, if you ask how I feel, I feel
quite comfortable, but then I'mgiving patients, you know,
multimodal analgesia andanesthesia on a day to day
basis.
I think anybody who'sapproaching, you know, using
multiple drugs for a patientmust recognize the drug
interactions and, and you must,you must work to mitigate those
(27:22):
interactions.
Fentanyl and all the otheropiates, potent respiratory
depressants.
As is methoxyfluorine.
So if I were going to have apainful transition, as you
suggest, and I wanted to addsomething, and I knew the
patient had opiates on board,opiates and volatiles are very
synergistic I would be that muchmore conscious and careful to
monitor the, the patient'srespiration.
(27:42):
It certainly wouldn't stop meusing it and, and let's say we
had a patient who we'd had to doa rapid extrication, they'd
already had some fentanyl ormorphine on board.
We then recognize, let's saythey've got a fracture
dislocation and the limb has gotvascular compromise.
We need to do a betterreduction.
Would I consider using methoxyfor that on top of other agents?
Absolutely.
And, and, you know, getting thepatient engaged and you know,
(28:05):
empowering them to help.
deal with their pain has got asignificant amount of value in
the field.
Patrick (28:11):
You implied that we're in a situation that has less or
no monitoring available.
Is there ever a situation inwhich you would consider it
necessary to have monitoringavailable before giving
methoxyfluorine?
Or is this fine on its own?
You're No problems.
I'm handing it out
Ross Hofmeyr (28:31):
I think
Patrick (28:31):
a conscious participatory patient.
Ross Hofmeyr (28:33):
yeah, yeah.
So in a, in an adult patientwho's got acute traumatic pain
and is conscious andcommunicative I, I think that
normal clinical monitoring,talking to the patient,
observing the patient Wouldwould be enough for me to be
comfortable.
I don't feel that we would needto have any kind of you know,
monitoring on the patient.
I would be cautious aboutembarking on doing a, you know,
(28:55):
Pediatric sedation using methoxywithout some kind of some kind
of monitoring.
But I think in the normalcontext of our wilderness
medicine and rescue, it's a,it's a very safe drug.
Patrick (29:08):
Okay.
Can you safely ambulate thepatient while they are using
methoxyfluorine?
I recall an image from perhaps alecture you gave which I think
there was perhaps a gentlemancrossing a river while
methoxyfluorine.
Tell me about that.
Patrick here with a quick sidenote, I found this clip from
(29:29):
Survivor and clipped it for you,and a link to that YouTube clip
is in the show notes.
Back to Ross.
Ross Hofmeyr (29:36):
Yeah.
So that actually was a signatureevent that, that work a lot of
us in the rest of the world upto the concept of Methoxy Fluor.
And I might be showing my grayhair a little bit here, but it
was an episode from the.
First series, I believe ofsurvivor.
And they had they were doingsurvivor down in Australia
where, as we said earlier, theFoxy Fluray has been in use for
(29:58):
a long time.
And one of the quite seriouscontenders to, to win the show.
Was was cooking in an open fire.
And, and he fell into the firewith, I think he lost his
balance.
And he sort of fell into thefire with his, with both hands.
And obviously, you know, themedical team was called in and
they had to evacuate this guyand the quickest way to get him.
Art was was to cross the shallowriver to a helicopter.
(30:20):
And there's this iconic image ofthis guy coming across the river
with this massive green whistlein his mouth.
You know, and the paramedicskind of holding him in his hands
as he, as he wades through.
And all of us in South Africawent, you are my brew.
Look at this.
They've got lack of, lack ofbongs there.
Hey.
And, and turned out it wasn'tmarijuana.
But it was, it was methoxy,Florin.
And that really sort of wentbing for many of us in the rest
(30:41):
of the world going, well, hangon a moment.
Why don't we have this?
We, we want this.
So would I ambulate a patient?
Yes, I would.
With the proviso again, it doesmake people often feel quite
lightheaded, feel a little bitdizzy.
I'm not going to imply that anyof the listeners of your very
august podcast would ever have,you know, tried something like
(31:02):
nitrous oxide in a, in anonclinical setting.
But if anyone ever has had aninhalational anesthetic, ever
had nitrous oxide it does giveyou this very sort of swirly
lightheaded feeling, quitepleasantly like being a little
bit tipsy.
And so I would quite happilyambulate a patient, but with
assistance, probably just, youknow, walking next to them,
(31:23):
making sure that they didn'ttrip over something.
Patrick (31:26):
I'm glad that you described that because I
personally certainly have no.
Sort of a similar experience.
When you're usingmethoxyfluorine, are there
environmental considerationssuch as temperature or altitude
which either limit orpotentially augment its use?
Okay.
Okay.
Ross Hofmeyr (31:58):
based in Bulawayo as an anesthetist early in his
career and, and there was thisobservation that Entonox or
nitrous oxide analgesia did notwork well at high altitudes.
You speak to the averageanesthetist from Denver or
Johannesburg or Mexico City,they'll tell you nitrous oxide
is a useless analgesic.
You speak to me in Cape Town orDurban or anywhere else on the
(32:18):
coast will say it's, it's a veryuseful drug and it has got a
potent analgesic effect.
We can talk about the greenhousegases and other things in a, in
a, in a different discussion.
So what Mike James did was hedid a nice study, he looked at
different altitudes and heshowed that yes, the effect of
nitrous oxide was diminishedwith altitude because as most of
(32:39):
us are familiar with, it's notso much the concentration of a
gas that has a biologicaleffect, but the partial pressure
thereof.
So the classic example is At sealevel, we breathe normal air
with 21 percent oxygen, and wedon't get hypoxic.
You go up to the summit ofEverest, you are breathing
normal air with 21 percentoxygen, but you get severely
(33:00):
hypoxic.
And the reason is that,obviously, the ambient pressure
on the summit of Everest isaround 28 kilopascals, so, you
know, it's less than a third ofsea level pressure.
So there's less than a third ofthe number of molecules that are
around for us to breathe.
Now, Nitrous oxide is deliveredas a gas, and so as the ambient
pressure decreases, if you givethe same concentration, the
(33:23):
partial pressure will decreaseand the effect will therefore
decrease.
And quite some time ago some,some erudite wilderness medics
and, and writers in the fieldhad proposed that methoxy might
be a useful agent forprehospital analgesia, but at
high altitude, it would sufferthe same degrading effect.
And so We, we set out to look atthis.
(33:44):
Now, the volatile agents, whenyou are breathing through an, a,
a vaporizer, a vaporizeractually works by generating
saturated vapor inside thedevice.
So our standard anestheticvaporizers for things like
subsevaflurane and isoflurane.
They've got a vaporizationchamber and they got a bypass
(34:05):
channel and we vary the amountof of gas that we give by
changing the amount that flowsthrough the vaporization chamber
or the bypass channel.
And we're very familiar withtalking about this in, in
percentage.
But actually what we should betalking about is we should be
talking about the partialpressure that we're developing.
So delivering rather.
So, I mean, about 10 years ago,actually, Mike James and Mike
(34:25):
Grocott of Everest fame.
And myself wrote a paper on thisin the British Journal saying,
well, we should be talking aboutthe map, the minimum alveolar
partial pressure rather than theminimum alveolar concentration
of a volatile agents, becausethen regardless of what device
we use and what altitude wedelivered it at, we would be
giving the same dose of agent.
Now, the, there's a usefuleffect with the vaporizers in
(34:49):
that as the density of the gaschanges.
Because you got this bypassgoing through a saturation
chamber, you end up giving adifferent concentration, but
actually pretty much the samepartial pressure.
So your vaporizers just workpretty much regardless of the
altitude that you use them at.
Now, because methoxyfluorane isa draw over vaporizer, we should
(35:10):
be delivering Again, the sat inthe same saturated vapor on
this.
No one had ever tested.
There's the one case report ofWilkes who'd used it a high
altitude and it actually seemedto work very well on.
So what we actually then didwith a grant from the WMS is we
put methoxy fluorine inhalersinto an altitude chamber at Duke
University at varying altitudeson.
(35:32):
We measured the amount of gaswe're getting out.
We actually measured that very,very accurately using a mass
spectrometer on.
We showed that At, across a widerange of altitudes, we delivered
exactly the same partialpressure.
So the device is delivering thesame amount regardless of
altitude, which is very useful.
And that means it fits in withour understanding of saturated
(35:53):
vapor, etc.
The caveat to all of that isthat if you know your science
well, you will know that thesaturated vapor pressure of, of
any substance, any liquid orgas, is fixed.
at a specific temperature.
So the only thing that changesSVP is the change in
temperature.
(36:14):
And that does, I believe, haverelevance for us in the
wilderness setting, because ifyou are giving the device to
somebody Outdoors here, perhapsin Crested Butte now where it's
a few degrees below zero Celsiusversus somebody who's just had a
hyena gnaw on their ankle in thefelt in Africa where it might be
30 degrees Celsius, then you aregoing to be delivering a
(36:37):
different Dosage to the patient.
We've got no actual experimentaldata to show how much the dose
varies We don't know what theeffect of holding the device and
in a hand to keep it warm is Andthat's really an area where we
could definitely have some somefurther work.
So altitude no difference.
It will work Temperature youmust anticipate decreasing
(36:59):
efficacy with decreasingtemperature
Patrick (37:03):
I seem to recall, and I looked this up in response to a
listener comment, but I thinkthat the freezing temperature of
the actual methoxyfluorineliquid is quite low, and perhaps
not clinically relevant here,but it did occur to me that that
problem with the vapor pressure,right, regardless of altitude,
at a colder temperature, you'regoing to produce less vapor from
(37:24):
that wick.
And the same question came tome, which was, okay, if you hold
it and warm it, could youachieve a reasonable dose yet?
The error that's being drawnacross it remains your
environmental air temperature.
So I don't know if it would beat all meaningful to to sort of
cuddle it with your hands andprotect it from the environment
(37:46):
or if that's just a pointlessexercise.
It sounds like there's abudding.
Research project here for anywilderness medicine fellows out
there who
Ross Hofmeyr (37:56):
Absolutely.
Patrick (37:56):
to write a grant and get some funding.
Ross Hofmeyr (37:59):
Absolutely.
As as my as my mentor, MikeJames would say this is an area
of opinion as yet unsullied byevidence
Patrick (38:08):
um, do you have any personal experience using it in
the cold
Ross Hofmeyr (38:12):
on myself, on patients.
Patrick (38:15):
either?
Ross Hofmeyr (38:16):
So yes, we have used it in cold environments.
and I've used it in I'm going tohave to estimate that what the
ambient temperature would havebeen probably would have been
between about minus two andminus five Celsius.
I apologize.
The American listeners that I'mnot fluent in Fahrenheit.
In the snow on a mountainside.
(38:38):
And the patient did describe aGood analgesic effect.
They did describe the sideeffects of the, of, of the
dizziness well lightheadednessrather let's call it.
So it was clear that the, thatthe drug was working whether it
would work in minus 10, minus20, I don't know, but we've used
it outdoors we've used it incold environments and it has
worked.
Patrick (38:59):
I think that in freedom units, that would be around,
like, 20 to 25 degreesFahrenheit.
When you are carrying it, do youkeep it close to your body if
you are in a colder environment?
Or do you attempt to keep itisolated from the elements?
Or is it just in your pack withyour other Okay,
Ross Hofmeyr (39:31):
that goes inside my jacket to prevent it from
freezing.
As, as you said, the freezingpoint of methoxyfurane is well
below zero Celsius, so actualfreezing of the agent is is not
really an issue.
And I think The con the, theissue really is how cold does it
get in that vaporization chamberand you know, will, will it
vaporize efficiently foranalgesic effect?
And I don't know the answer tothat question when we're
(39:53):
talking, you know, deep Sub-Zerotemperatures.
Patrick (39:57):
it really sounds like it's a, it's quite an ideal
medication for that the prehospital environment because it
requires such Little access,it's so easy to use, it's
titrated by the patient.
Are there downsides that you seeto it?
Ross Hofmeyr (40:13):
So the first one that comes to mind particularly,
you know, coming from an Africansetting is, is cost.
In.
In my South African rands, amethoxyfluorine combo kit with
the inhaler and two vials isprobably around a thousand times
more expensive than a, than anampoule of morphine which, you
(40:34):
know, in our, in our governmenthospital practice costs next to
nothing.
So, you know, the cost, the costis definitely higher.
There's a theoretical downsidein terms of environmental
contamination, and I mean, youknow, the greater global
environment although the amountof methoxy that we use in the
environmental dwell time ofmethoxy makes it a fraction of
(40:56):
the risk of you know, othergreenhouse gases like nitrous
oxide.
Another small downside isalthough the, the delivery
device itself is very light, itis somewhat bulky to carry.
So you could carry a couple ofsyringes and multiple ampules of
you know, opiates and otherthings for the bulk that you
need to, to carry in Methoxycombo kit on the plus side, they
(41:17):
are, they're very, very robust.
You know, they can get kickedaround and thrown around in a
pack.
The, the little ampule itself isvery, very tough.
So it doesn't get, I mean, I'venever.
Broken one accidentally evenwhen, you know, dropping packs
out of vehicles, other thingslike that other downsides, not,
not a whole lot.
I mean, it becomes another thingthat you have to carry another
(41:38):
thing that you have to disposeof.
I tend to throw mine in theplastic recycling, and that's
the end of that.
Patrick (41:44):
Okay.
Very good.
Well, I appreciate you takingthe time to discuss this with
me.
And for us, it's been funwatching the.
Sunset behind you in Colorado asI'm here in Hawaii where the sun
is definitely still up thanksfor for making the time to join
us on for For future episodes.
You're a wealth of knowledge
Ross Hofmeyr (42:06):
Well, thanks very much, Patrick.
And yeah, if I can encourage thelisteners that if they haven't
gone and had a look at the WMSacute pain practice guidelines
for which Patrick is the thelead author and really lit the
fire under all of us to get thatdone, then that, that those
guidelines are a really, reallygreat resource.
And yeah.
If you're going to read onething after listening to this
(42:28):
conversation, then open up theWMS CPG.
They're free.
They're online.
And if anyone does want to lookme up and reach out for more
information, I've got quite alot of stuff that you know, I
can send out to people.
My email is easy.
It's Ross at wild medics with anX.
com.
Podcast description.
Patrick (42:49):
Yeah, we'll put links to everything I can find about
you down there, Ross, so thatyou can be bothered to no end by
our listeners.
Ross Hofmeyr (42:58):
Fantastic.
Thank you.
Patrick (43:00):
And that's a wrap on my conversation with Dr.
Hoffmeier.
Thanks again, Ross, for joiningus on the show.
I really appreciate the time andthe expertise, and I hope that
everyone listening out therelearned something.
At times Ross gets deep.
I hope that everyone out therefound something that they can
take away or found someinspiration.
(43:23):
It's always great to learn more,expand our boundaries, expand
the toolkits that we haveavailable to us for managing
pain in austere environments.
As I mentioned with Ross, all ofthe links can be found down in
the show notes, includingpictures of the green whistle
and links so that you canconnect with Ross and his
(43:46):
company, Wild Medics, if you'reinterested to do so.
As I mentioned in theintroduction, thanks so much to
Eddie and Aaron for thequestions that created this
episode.
And I would encourage all of youto continue to reach out.
It's wildernessmedicineupdatesat gmail.
com, even if you just want tosay, Hey, give a shout out, or
(44:06):
if you have specific questions,things that we can dive into
more, because if you have aquestion, other people have a
question and there's no suchthing as stupid questions here.
We can always take it to thatnext deeper level.
I'm still not on any socialmedia because I just can't
handle that, but I do appreciateit.
(44:26):
If you give the show a rankingor a review on iTunes or
Spotify, that helps this showget out to reach more listeners.
As I've mentioned before, thisis a passion project.
I'm not making money on it.
I am losing money on it, but Ienjoy bringing this content to
you guys and hearing back thatit is delivering value.
To you.
So thank you for listening.
(44:46):
And as always, another way youcan support the show is to share
this episode with someone youthink might appreciate it, or
maybe they want to hear aboutavalanche physiology or how to
make tourniquets out of spaceblankets that episode you think
they might appreciate.
Share it with your fellow nurse,doctor, paramedic, medical
student, nursing student, SARmember, or fellow
(45:09):
recreationalist who just wantsto learn more and be prepared
for those situations in theoutdoors.
Until next time, stay fit, stayfocused and have fun.
And there's this iconic image of this guy coming
(00:02):
across the river with thismassive green whistle in his
mouth.
You know, and the paramedicskind of holding him in his hands
as he, as he wades through.
And all of us in South Africawent, you are my brew.
Look at this.
They've got lack of, lack ofbongs there.
Hey.
And, and turned out it wasn'tmarijuana.
But it was, it was methoxy,Florin.
And that really sort of wentbing for many of us in the rest
of the world going, well, hangon a moment.
(00:23):
Why don't we have this?
We, we want this.
Patrick (00:26):
Hello, and welcome back to Wilderness Medicine Updates,
the show for providers at theedges.
I'm your host, Dr.
Patrick Fink, and I'm happy tobe talking today about
methoxyfluorine.
What is methoxyfluorine, youmight ask?
And if you ask that question,you probably live in the United
States.
(00:47):
Methoxyflurane is an anestheticgas that can be used to treat
pain in the wildernessenvironment.
It comes in a nifty littlepackage, and we're going to talk
a lot more about that, and I'msuper happy today to be joined
on the show by Dr.
Ross Hoffmeier.
Ross is an anesthesiologist wholives and works in an academic
(01:09):
setting in South Africa, but hehas a much more varied and
interesting wilderness practicethat goes well beyond the
confines of the hospital walls.
As you'll discover, Ross is awealth of information about
methoxyfluorane, its prior usein anesthesia, and its use now
in the wilderness and prehospital setting, both its
(01:30):
benefits as well as somedownsides and some settings
where it may or may not beterribly effective.
If you want to learn more aboutRoss, What this medication is,
how it's used, how it fits intohis pain management plan, ideal
settings for its use,contraindications, and most
importantly, what made him saythat in the cold open, I owe a
(01:53):
big thanks to Aaron and Eddie,two listeners who wrote in with
questions about methoxyfluraneafter our last episode on
ketamine.
I always love getting listenerquestions and there's more in
the inbox, some.
Conversations that have beenongoing that are going to bring
some interesting episodes to youguys.
So please continue to reach outas always wilderness medicine
(02:14):
updates at gmail.
com and I'll hit you with thatagain in the outro.
Without further ado, here is Dr.
Ross Hoffmeier.
Ross Hofmeyr (02:23):
Mozambique was fantastic.
We.
flew into the backside of atropical storm and into a
country undergoing civil unrestwith people thinking it was
going to be going into a civilwar.
And it was absolutely blissfuland peaceful.
Sea was a bit heavy some quitebig swells, but we got some
great diving done and the peoplewere fantastic and we had no
(02:43):
problems.
So it was really nice.
Patrick (02:46):
Great.
And now you're at the WildernessMedicine Society Conference in
Crested Butte.
Ross Hofmeyr (02:51):
That's right.
Yeah, I just wrapped up here inColorado.
If I look a little bit pink inthe face, it's because it's been
an absolute bluebird, sunshinyday here on the slopes and I've
just got in about 20, 000vertical feet of skiing in for
the day.
Patrick (03:06):
Fantastic.
It sounds like a toughlifestyle.
I know that your, your job byday is an anesthesiologist.
How do you describe the rest ofyour roles and how that
interacts with the world ofwilderness medicine?
Okay.
Okay.
Ross Hofmeyr (03:24):
as an anesthesiologist or anesthetist,
as you say.
I'm based at a universityhospital in Cape Town in South
Africa.
and we'll see first hearttransplant.
My day job there is as acardiothoracic anesthesiologist.
And I do a lot of airway stuffas well.
(03:45):
And so that's what pays thebills and brings home the bacon.
But wilderness medicine has beenmy passion for a very long time
after.
Growing up through search andrescue as a, as a student in
training and then as a juniordoctor I served as the
expedition leader and and doctorfor our South African research
team in Antarctica winter overthere.
And I've been involved inwilderness medicine and
(04:07):
wilderness rescue ever since.
And in the early noughtiesMountain Rescue colleague and I
started a small company, whichhas remained small called Wild
Medics.
We're based in Cape Town inSouth Africa, and we've been
providing wilderness medicalsupport and particularly over
the last number of years,wilderness medical training with
an African focus and flavor butobviously, you know, trying to
(04:31):
incorporate the, the bestinternational practices there as
well.
So, Wilderness medicine is my mymistress and my passion project.
And the anesthesia is my, my dayjob.
Patrick (04:41):
I'm glad that you're the person to come on and
discuss this topic on thepodcast.
because after the last podcaston ketamine hospital pain
control, I got a number ofquestions from listeners who
wanted to know more aboutmethoxyfluorine.
when we were putting togetherthe pain guideline, you were
kind of the gas anesthesia guybut methoxyfluorine is not
(05:03):
something familiar to me.
It's.
Not available in the UnitedStates outside of some ongoing
clinical trials.
So I wanted to begin sort of asthe I'll play the novice here
that I want to know what what ismethoxyfluorine?
Where where does this fit intothe world of pain control and
why have I never heard of it?
(05:24):
Silence.
Ross Hofmeyr (05:37):
a volatile anesthetic agent.
It's an old drug.
The first published clinicaltrials were in the late fifties,
early sixties.
It, so it's been around for avery long time.
It is fairly unique amongst theinhalational anesthetic agents
in that it also provides ananalgesic effect.
So most of our Inhaledanesthetic agents, particularly
(06:00):
fluorinated drugs the ones thateveryone's very familiar with
would be things like isoflurane,sivoflurane, desflurane, those
are the ones that are in modernuse.
joining us people probably willbe familiar with, and we'll
definitely talk about this a bitmore, of course, is nitrous
(06:22):
oxide.
And that's commonly been used asan analgesic agent when it's
mixed in a 50 50 concentrationmix with oxygen, and that's
known as oxen that's been usedfor labor analgesia.
It's been used in pre-hospitalanalgesia.
And, and, you know.
People are very familiar withthat concept of providing an
inhalational drug, which gives,it gives pain control.
So methoxy and nitrous oxidereally are the only anesthetic
(06:46):
inhaled agents we have that givethat analgesic property.
Now, an astute listener is goingto say, well, hang on a moment.
You can't actually anesthetizesomebody with nitrous oxide
because the, the, the Mac or theminimum alveolar concentration
of the gas, which you need tobreathe at sea level to render
somebody unconscious is around104%.
(07:06):
and somebody 104 percent of ananoxic show you've got larger
problems than anesthetizingthem.
You're just going to euthanizethem.
But the concept of givingsomeone a gas, which has got
analgesic properties, I think isfamiliar to us from, from
Entonox.
Now, methoxyfluorine is actuallyright at the other end of the
(07:27):
spectrum in terms of potency.
So provided only a long timeago.
When alveolar concentration,that's really the concentration
at sea level of that gas in abreathing mixture, which will
render 50 percent of, ofpatients or 50 percent of
subjects non responsive to asurgical stimulus.
(07:49):
So you give the person that muchgas and half of people won't
move or show any sign of asurgical incision.
Now we add other agents to tryand We work with those values
and we monitor depth ofanesthesia, et cetera and we're
familiar with our everydayvolatile agents, something like
Desflurane that a lot of peoplemay use the, the MAC value is
(08:09):
around 6%.
Sevaflurane is a little bit morepotent.
The MAC value of that is around.
Let's say 2 percent for ease ofdiscussion.
Isoflurane, even more potentaround 1.
2%.
And the MAC value ofmethoxyfluorane So, is 0.
16%.
So it's actually a very, verypotent anesthetic drug The
(08:29):
potency just in terms of the MACvalue is that ignores how much
of the, of the volatile agent isabsorbed and, and dissolved into
the bloodstream and particularlyabsorbed into the fat.
So that has got a lot of thethe, the lipid the has a lot to
do with the, the speed of onsetof the, of the different agents.
the so methoxyfluorine, althoughit's very, very potent.
(08:51):
Has actually, it's actually alittle bit of a slow agent to
anesthetize patients with.
So when it came into clinicalpractice, and now we're talking,
you know, 50s, 60s it was quitepopular because Because a lot of
the agent is becoming absorbedit then takes a very long time
to, to come back out of thesystem and that gives you a
really nice, long analgesictail.
(09:12):
So people would often mixvolatile agents and they would
use methoxy plus something elseto get the patient off to sleep,
turn the other agent off, runthe patient on methoxyfluorine,
and then at the end of theprocedure, they may take quite a
while to wake up, but they'vegot this beautiful analgesic
tail.
So that's really handy.
Okay.
(09:34):
And that's because it's nolonger in clinical use for
anesthesia.
The problem with using it as ananesthetic agent is that if you
use it at high concentrationsfor long durations, it has got a
to take nephrotoxic effect.
So it directly causes a ininjury.
In fact, I'm not quite thatsimple.
it in.
(09:54):
chemical byproducts, which causea, cause a kidney injury.
about we now know from the, fromthe literature, to is that that.
and I'm A clinical nephrotoxiceffect tends to emerge at around
five MAC hours worth of dosage.
So if you think of administeringone MAC to keep a patient asleep
for five hours, that's the kindof dose that you need to cause a
(10:15):
clinically evident nephrotoxicevent.
And biochemical nephrotoxicityis around 2.
5 Okay.
problem, of course, is that themoment that people started
seeing these renal injuriescoming out, there's a greater
risk if you've got underlyingrenal disease and very, very
(10:38):
rapidly, the Toxifluranedeveloped a bad rap and quite
quickly it was taken off themarket as an anesthetic agent.
So that's, that's where itdisappeared to.
It was, however, even at thattime in use as an analgesic
agent and it was being used in avery, very simple draw over
(10:58):
vaporizer.
So effectively, you think abouta tube with some wicking
material inside, you pour someof the liquid methoxyfluoride
inside, the wick helps to spreadit around, the gas then
vaporizes inside the inhaler,and you suck through it, and you
get a, you get an inhaled dose.
In fact, there was a, a devicewhich it was called the the
analgizer, be careful topronounce that correctly if you
(11:20):
read the packaging and it wasbeing used for for labor
analgesia and was also beingused for pre hospital analgesia.
And in fact, the, the typicallabor analgesic dose was up to
15 milliliters or 15 CC ofliquid methoxyfluorine into the
inhaler and all that number 15in your head, because Okay.
(12:05):
the full duration of the last 50or 60 years.
And there's extensive literatureand.
You have tens of thousands ofdocumented uses there as a pre
hospital analgesic, which makesit very attractive for the kind
of work that that you and I do.
Patrick (12:20):
So the current manifestation is a device which
contains some set amount ofmethoxy fluorine, which can be
used in the field, sort of likeprobably the best analogy to the
younger humans listening wouldbe something like a vaporizer
type device, right?
Like it quite literally has avaporizable liquid that sits on
(12:42):
a wick.
And as you breathe through it,it draws off some methoxy
fluorine.
But you're only achieving thelevel of the inhalational agent
that will deliver analgesia,right?
You can't possibly pull on thisthing hard enough to make
yourself pass out.
Am I correct?
Ross Hofmeyr (12:58):
You're mostly correct.
So in fact, the device itselfthat, that now on the market,
and it's sold in different areasof the world under slightly
different names.
Some, some places call itPenthrox, some call it Penthrop,
some call it Penthrane butpretty much the same thing.
And it now comes in a, in a biggreen plastic.
Tube that looks a lot like awhistle.
(13:18):
So some people talk about thegreen whistle.
Frankly, you know, a big greenthing that you suck on, which
makes you quite lightheaded andfeel a bit high is, as you say,
very easily approachable conceptto many people the younger
people and probably lots ofpeople here in Colorado but uh,
Patrick (13:34):
Okay.
Ross Hofmeyr (13:52):
on the device.
There were some concerns
Patrick (13:54):
I,
Ross Hofmeyr (13:55):
particularly the pre hospital community in
Australia that Becausemethoxyfluorine itself is
incredibly aromatic you, you cansmell the tiniest concentration
of it in the air around you.
Patrick (14:07):
of
Ross Hofmeyr (14:08):
about people who were sitting in the back of
ambulances with patients whowere breathing on these green
whistles that they might begetting a, an occupational
exposure,
Patrick (14:16):
much.
Ross Hofmeyr (14:17):
to methoxyfluorine.
And so the, the modern device isactually packaged with an, a
little activated charcoalabsorber.
That clips into the exhalationvalve.
So it's got a one way valve.
So when you, when you suck onit, it sucks through the device.
And when you blow on it, itblows out through an exhalation
valve.
And you can put this littleabsorber onto it.
And, and that then is supposedto capture a lot of the
(14:39):
methoxyphore in it, but go outinto the environment.
And it's It's worth that Imentioned the absorber device
because you can actually varythe dose that the patient is
receiving by getting them to, toclose the the air entrainment
hole that's on the absorber.
And if you take the absorber offcompletely, which for us in a
wilderness environment wherewe're out in the fresh air would
(15:00):
be entirely safe.
Then they actually get a muchlower dose of the methoxy
because it.
It entrains some air through theabsorber hole on, and we
actually documented this andquantified this in some work
that I did a few years ago atDuke University in their
altitude chamber.
Unfortunately, I can't send youto the publication of that work.
It's been presented at the WMS.
It was supported by a grant fromthe Wilderness Medical Society,
(15:24):
but we showed that actually youcan vary the dose quite
significantly by eitheroccluding the hole, adding the
absorber or, or leaving it open.
So you asked whether.
you can give somebody too muchwith with methoxyphorin inhaler?
And the short answer is that foran adult patient breathing
normal adult tidal volumes theanswer is no.
(15:44):
If you use the standard dosethat comes in the vial, it's a
three mil vial.
Remember we said earlier.
That for labor analgesia, theywere giving 15 milliliters.
So it's literally a fifth of thedose that was being used there.
That gives you around 0.
3 years, 0.
26 to 0.
29 Mac hours worth of doseexposure, and that's, that's
(16:06):
enough to make you feel a littlebit dizzy, maybe a bit
lightheaded, sometimes peoplecomplain of a bit of nausea or a
bit of headache but it'scertainly.
And the best, the bestexpression that someone said to
me is it makes me feel goofed.
You just feel a little bit dizzyand out of it.
But obviously it takes away alot of your, a lot of your pain.
For a normal size adultbreathing on the device, they're
not going to be able to get ananesthetic dose.
(16:27):
So that's really quite safe.
There is some concern andthere've been a number of papers
published where they've usedthis for pediatric analgo
sedation and pediatricprocedural sedation.
And in fact, If somebody isunable to breathe through their
mouth to breathe with thedevice, in fact, the outer
diameter of the inhaler itselffits perfectly into the inner
(16:52):
diameter of a normal medicalface mask, so your anesthetic
face mask, and so in some ofthose studies, they have They
put it into a face mask and heldthat for for children.
And there with a much smallertidal volume, actually, there is
a risk of approaching ananesthetic dose.
One of the effects ofmethoxyfluorine, of course, the
side effects is it causesdrowsiness.
(17:13):
Well, it's an anesthetic, sowe're not really surprised.
It's also quite a potentrespiratory depressant.
And so our.
Our common practice and ourcommon guidance is that it
should, in a non monitored orout of hospital setting, it
should be self administered by apatient.
So if they start to get a littlebit drowsy or their respiratory
rate starts to decrease, they'renaturally going to take it out,
(17:34):
drop it, or they're going toinhale less of it.
Rather than than holding it withwith a face mask.
So that's the, that's thecaveat.
It is not going to put you tosleep if you're using it as an
analgesic in an adult patient.
It's in most countries where itis currently available.
It's off label for pediatrics inany case.
But the proviso is don't attachit and breathe it through a
mask.
Patrick (17:56):
Much like nitrous oxide, we give the patient the
control over the mask here,you're having them hold the
whistle.
And so if they're dosingthemselves too heavily and
becoming goofed, as you said,they will no longer be able to
hold it to their mouth.
Yes.
Ross Hofmeyr (18:10):
Absolutely.
Patrick (18:11):
so just want to confirm my understanding.
You can modulate the dose byessentially controlling how much
air is co inspired with theanesthetic agent.
So if you were to the.
air intake, then all of the gaswhich is being inspired is
coming across themethoxyfluorine wick and get
your highest level of, yourhighest dose.
(18:34):
Allow the, allow that to be opento air, you get sort of a
moderate dose, and then if youtake the whole off, you're going
to entrain further more air andresult in a further lower dose,
is that correct?
This transcript
Ross Hofmeyr (18:46):
That's that's 100 percent correct.
So the highest doses, if youinclude the entrainment hole,
Patrick (18:51):
Dakota is
Ross Hofmeyr (18:52):
if you leave the entrainment hole open with the
scrubber on, you get a slightlylower dose.
And if you take the scrubberoff, you get the lowest dose.
And
Patrick (18:59):
award
Ross Hofmeyr (18:59):
it's so aromatic
Patrick (19:01):
Doctor of
Ross Hofmeyr (19:02):
who's practiced a little bit of anesthesia will
probably have experienced
Patrick (19:05):
Human
Ross Hofmeyr (19:06):
a gas induction for a child using something like
Sivaflurane.
If you put a mask on and youcrank that right up to a high
concentration and the firstbreath or two is really
concentrated volatile, peoplewill often find that quite
irritant.
They'll have a bit of a cough.
They might balk at that.
And it's quite similar for mewith Mesoxiflurane.
I often tell people.
To take their first one or twosmall breaths, keep the
(19:28):
entrainment hole open, get afeel for the taste and the smell
of the methoxyfluorine, see ifit's having an effect on their
pain.
And the onset of analgesia isactually quite rapid.
It's within you know,
Patrick (19:41):
Yeah.
Ross Hofmeyr (19:44):
getting used to that, if they're finding that
they want more analgesic effectto then close that hole and to
take nice, deep slow breathsthrough the inhaler.
Patrick (19:53):
Okay, so now I think that's a pretty good overview of
the nuts and bolts of theanesthetic background of
methoxyfluorine, as well as theactual mechanics of the inhaler.
And I'll put a link in the shownotes to pictures of both the
older green whistle and thenewer device that has come out.
(20:13):
Where does.
Methoxyfluorine fall into yourpractice for pre hospital pain
control?
Where does it fit in with oralanalgesics, IV, or, or stronger,
you know, narcotic typemedications?
In what settings are youchoosing to use it?
Ross Hofmeyr (20:29):
Okay.
That's a great question.
So the first thing to recognizeis that we're limited in the
dose that we can administer.
So we're giving about a threemil initial dose and depending
on how rapidly somebody isbreathing and, and you know,
whether they're occluding theholes in the So the breath
they're taking, that gives youabout 20 to 30 minutes worth of
analgesia.
And then we can repeat that doseonce if we're following the the
(20:52):
package insert.
So you're really looking at ananalgesic intervention, which is
it's immediately available.
It's very quick to prepare that,you know, the device can be
active within 20, 30 seconds, ifyou, if you're familiar with
using it and it's giving you,let's say 32.
To 60 minutes of analgesia thetwo main areas that I like to
(21:15):
use it in my practice are numberone Patients who particularly in
the wilderness setting have hada traumatic injury and they need
potent analgesia.
So it is a potent analgesic.
I wouldn't use it for you know,someone who's got a small
laceration that just needs a bitof care.
It's a potent analgesic.
It's immediately available to beadministered.
It doesn't require me to get outIV access.
(21:36):
It doesn't require me to openany vials.
I don't have to draw up anydrugs.
I don't have to check anyconcentrations.
It's very much.
Open the packaging, pour in themethoxy, give the patient a
brief instruction, and allowthem to start breathing.
And that then frees me up tocontinue with my other
interventions.
So it's a very good bridge toproviding IV analgesia, or
(21:59):
perhaps intramuscular analgesiaif you're dealing with less
severe pain, but as you wellknow, lots of considerations
around giving giving IM drugs.
It's excellent in giving youthat first 20 minutes while you
are completing your primary andmaybe secondary survey,
establishing IV access, and thenstarting to titrate in you know,
rapid acting or a more longeracting analgesic, whether that's
(22:23):
going to be something likeacetaminophen or it's going to
be stronger in opiate orketamine or other things.
So that's the first reallyuseful space is an analgesic
bridge.
You do need a conscious,cooperative patient, and they do
need to have moderate to severepain but it gives you that first
20 to 30 minutes.
Patrick (22:39):
Okay.
Ross Hofmeyr (22:42):
I'll say this with caution because obviously it
depends on the regulatoryenvironment where you're working
but we have trained a lot of ourwilderness first responders our
SAR personnel, and then we'vetrained some of our non
Patrick (22:54):
Okay.
Ross Hofmeyr (22:57):
medically trained tour guides and wilderness
guides and expedition leaderswho have got wilderness first
aid training, wilderness firstresponder training and are
working fairly independently inremote areas, we've trained many
of them to administermethoxyfluorane as an analgesic
agent.
We've got a very quick littlechecklist.
And so if I've got a team whoare doing a guided
(23:19):
investigation, Motorcycling tripthrough Cambodia somebody comes
off with a shoulder dislocationor a tibfib fracture and they're
in severe pain, then that teamcan immediately administer
methoxyphorin while they'restabilizing the patient,
splinting, et cetera, et cetera.
And often that gets you throughthat first really painful period
of of immobilization and soforth.
Patrick (23:39):
much.
Ross Hofmeyr (23:49):
More seldom, but it does definitely have some
efficacy and that is forprocedural analgoacidation.
If you're doing a painfulprocedure in a remote
environment and you've got very,very limited monitoring.
And Matt Wilkes has got a lovelycase report of using methoxy for
placement of a suprapubiccatheter at four and a half
thousand meters altitude, whereit was, it was used for exactly
(24:09):
that that purpose.
So and again, there's plenty ofpublications in adults and kids
of using methoxy for proceduralsedation.
So I think that's a reasonableindication, although I will say
again, the caveat depends onyour regulatory environment.
In South Africa, for instance,it's not actually licensed for
procedural sedation.
It's only licensed for acutetraumatic pain.
Patrick (24:31):
In places where it is available, let's stick with
South Africa because you're mostcomfortable with that.
Does it require a prescriptionto obtain it?
And how does one go aboutgetting a hold of
methoxyfluorine?
Ross Hofmeyr (24:42):
Yeah.
So in South Africa, it's a, it'sa prescription drug.
It's it's a schedule five out ofseven level scheduling.
So it's actually quite a highschedule drug.
That's because they didn'tchange the scheduling when it
came back from its, you know,anesthetic use.
That does require aprescription.
And so it's supposed to be usedon a named indication, named
(25:04):
patient basis.
The way that we get around thatfor our wilderness usage is that
we have a very defined protocol,and a non
Patrick (25:14):
by
Ross Hofmeyr (25:22):
this is a situation.
The patient's past thechecklist.
Can I go ahead and give them theFoxy?
And, and we then prescribe it aspart of a, of an expedition kit.
Much the same way that we do alot of our other prescription
medications that go into thosekits.
Patrick (25:34):
And in that kit or in your personal med kit that you
might either carry with yourecreationally or as a
responder, are you carrying justthe two vials of methoxyfluoride
or do you carry more?
Ross Hofmeyr (25:45):
Yeah, I carry an inhaler and well, the delivery
device and two vials becausethe, the likelihood of needing
more than one.
inhaler for one patient in mynormal practice is quite low.
I do obviously have access toother agents, so if I did have
another patient where I didn'thave IV access and I had acute
severe pain, I'd have options todo things like intranasal
(26:07):
ketamine or intranasal fentanylother things like that.
And those, those still remainreally, really good options.
I'm not advocating that, youknow, methoxy is better than
other drugs.
There's some, there's some goodliterature out there.
But certainly in terms of Theease of deliverability by less
trained personnel and the easeof freeing up your hands so you
(26:29):
can do other tasks,
Patrick (26:30):
CastingWords
Ross Hofmeyr (26:32):
there.
Patrick (26:33):
How do you feel about administering methoxyfluorine to
a patient who has alreadyreceived other centrally acting
medications?
you've, you've providedintramuscular fentanyl or
intranasal ketamine, and nowyou're approaching a painful
transition or splinting or whathave you, you want to consider
using methoxyfluorine forbreakthrough of that next level
(26:54):
of analogous sedation.
How do you feel about thecombination of those and how do
they play together?
Ross Hofmeyr (27:00):
So I think From, if you ask how I feel, I feel
quite comfortable, but then I'mgiving patients, you know,
multimodal analgesia andanesthesia on a day to day
basis.
I think anybody who'sapproaching, you know, using
multiple drugs for a patientmust recognize the drug
interactions and, and you must,you must work to mitigate those
(27:22):
interactions.
Fentanyl and all the otheropiates, potent respiratory
depressants.
As is methoxyfluorine.
So if I were going to have apainful transition, as you
suggest, and I wanted to addsomething, and I knew the
patient had opiates on board,opiates and volatiles are very
synergistic I would be that muchmore conscious and careful to
monitor the, the patient'srespiration.
(27:42):
It certainly wouldn't stop meusing it and, and let's say we
had a patient who we'd had to doa rapid extrication, they'd
already had some fentanyl ormorphine on board.
We then recognize, let's saythey've got a fracture
dislocation and the limb has gotvascular compromise.
We need to do a betterreduction.
Would I consider using methoxyfor that on top of other agents?
Absolutely.
And, and, you know, getting thepatient engaged and you know,
(28:05):
empowering them to help.
deal with their pain has got asignificant amount of value in
the field.
Patrick (28:11):
You implied that we're in a situation that has less or
no monitoring available.
Is there ever a situation inwhich you would consider it
necessary to have monitoringavailable before giving
methoxyfluorine?
Or is this fine on its own?
You're No problems.
I'm handing it out
Ross Hofmeyr (28:31):
I think
Patrick (28:31):
a conscious participatory patient.
Ross Hofmeyr (28:33):
yeah, yeah.
So in a, in an adult patientwho's got acute traumatic pain
and is conscious andcommunicative I, I think that
normal clinical monitoring,talking to the patient,
observing the patient Wouldwould be enough for me to be
comfortable.
I don't feel that we would needto have any kind of you know,
monitoring on the patient.
I would be cautious aboutembarking on doing a, you know,
(28:55):
Pediatric sedation using methoxywithout some kind of some kind
of monitoring.
But I think in the normalcontext of our wilderness
medicine and rescue, it's a,it's a very safe drug.
Patrick (29:08):
Okay.
Can you safely ambulate thepatient while they are using
methoxyfluorine?
I recall an image from perhaps alecture you gave which I think
there was perhaps a gentlemancrossing a river while
methoxyfluorine.
Tell me about that.
Patrick here with a quick sidenote, I found this clip from
(29:29):
Survivor and clipped it for you,and a link to that YouTube clip
is in the show notes.
Back to Ross.
Ross Hofmeyr (29:36):
Yeah.
So that actually was a signatureevent that, that work a lot of
us in the rest of the world upto the concept of Methoxy Fluor.
And I might be showing my grayhair a little bit here, but it
was an episode from the.
First series, I believe ofsurvivor.
And they had they were doingsurvivor down in Australia
where, as we said earlier, theFoxy Fluray has been in use for
(29:58):
a long time.
And one of the quite seriouscontenders to, to win the show.
Was was cooking in an open fire.
And, and he fell into the firewith, I think he lost his
balance.
And he sort of fell into thefire with his, with both hands.
And obviously, you know, themedical team was called in and
they had to evacuate this guyand the quickest way to get him.
Art was was to cross the shallowriver to a helicopter.
(30:20):
And there's this iconic image ofthis guy coming across the river
with this massive green whistlein his mouth.
You know, and the paramedicskind of holding him in his hands
as he, as he wades through.
And all of us in South Africawent, you are my brew.
Look at this.
They've got lack of, lack ofbongs there.
Hey.
And, and turned out it wasn'tmarijuana.
But it was, it was methoxy,Florin.
And that really sort of wentbing for many of us in the rest
(30:41):
of the world going, well, hangon a moment.
Why don't we have this?
We, we want this.
So would I ambulate a patient?
Yes, I would.
With the proviso again, it doesmake people often feel quite
lightheaded, feel a little bitdizzy.
I'm not going to imply that anyof the listeners of your very
august podcast would ever have,you know, tried something like
(31:02):
nitrous oxide in a, in anonclinical setting.
But if anyone ever has had aninhalational anesthetic, ever
had nitrous oxide it does giveyou this very sort of swirly
lightheaded feeling, quitepleasantly like being a little
bit tipsy.
And so I would quite happilyambulate a patient, but with
assistance, probably just, youknow, walking next to them,
(31:23):
making sure that they didn'ttrip over something.
Patrick (31:26):
I'm glad that you described that because I
personally certainly have no.
Sort of a similar experience.
When you're usingmethoxyfluorine, are there
environmental considerationssuch as temperature or altitude
which either limit orpotentially augment its use?
Okay.
Okay.
Ross Hofmeyr (31:58):
based in Bulawayo as an anesthetist early in his
career and, and there was thisobservation that Entonox or
nitrous oxide analgesia did notwork well at high altitudes.
You speak to the averageanesthetist from Denver or
Johannesburg or Mexico City,they'll tell you nitrous oxide
is a useless analgesic.
You speak to me in Cape Town orDurban or anywhere else on the
(32:18):
coast will say it's, it's a veryuseful drug and it has got a
potent analgesic effect.
We can talk about the greenhousegases and other things in a, in
a, in a different discussion.
So what Mike James did was hedid a nice study, he looked at
different altitudes and heshowed that yes, the effect of
nitrous oxide was diminishedwith altitude because as most of
(32:39):
us are familiar with, it's notso much the concentration of a
gas that has a biologicaleffect, but the partial pressure
thereof.
So the classic example is At sealevel, we breathe normal air
with 21 percent oxygen, and wedon't get hypoxic.
You go up to the summit ofEverest, you are breathing
normal air with 21 percentoxygen, but you get severely
(33:00):
hypoxic.
And the reason is that,obviously, the ambient pressure
on the summit of Everest isaround 28 kilopascals, so, you
know, it's less than a third ofsea level pressure.
So there's less than a third ofthe number of molecules that are
around for us to breathe.
Now, Nitrous oxide is deliveredas a gas, and so as the ambient
pressure decreases, if you givethe same concentration, the
(33:23):
partial pressure will decreaseand the effect will therefore
decrease.
And quite some time ago some,some erudite wilderness medics
and, and writers in the fieldhad proposed that methoxy might
be a useful agent forprehospital analgesia, but at
high altitude, it would sufferthe same degrading effect.
And so We, we set out to look atthis.
(33:44):
Now, the volatile agents, whenyou are breathing through an, a,
a vaporizer, a vaporizeractually works by generating
saturated vapor inside thedevice.
So our standard anestheticvaporizers for things like
subsevaflurane and isoflurane.
They've got a vaporizationchamber and they got a bypass
(34:05):
channel and we vary the amountof of gas that we give by
changing the amount that flowsthrough the vaporization chamber
or the bypass channel.
And we're very familiar withtalking about this in, in
percentage.
But actually what we should betalking about is we should be
talking about the partialpressure that we're developing.
So delivering rather.
So, I mean, about 10 years ago,actually, Mike James and Mike
(34:25):
Grocott of Everest fame.
And myself wrote a paper on thisin the British Journal saying,
well, we should be talking aboutthe map, the minimum alveolar
partial pressure rather than theminimum alveolar concentration
of a volatile agents, becausethen regardless of what device
we use and what altitude wedelivered it at, we would be
giving the same dose of agent.
Now, the, there's a usefuleffect with the vaporizers in
(34:49):
that as the density of the gaschanges.
Because you got this bypassgoing through a saturation
chamber, you end up giving adifferent concentration, but
actually pretty much the samepartial pressure.
So your vaporizers just workpretty much regardless of the
altitude that you use them at.
Now, because methoxyfluorane isa draw over vaporizer, we should
(35:10):
be delivering Again, the sat inthe same saturated vapor on
this.
No one had ever tested.
There's the one case report ofWilkes who'd used it a high
altitude and it actually seemedto work very well on.
So what we actually then didwith a grant from the WMS is we
put methoxy fluorine inhalersinto an altitude chamber at Duke
University at varying altitudeson.
(35:32):
We measured the amount of gaswe're getting out.
We actually measured that very,very accurately using a mass
spectrometer on.
We showed that At, across a widerange of altitudes, we delivered
exactly the same partialpressure.
So the device is delivering thesame amount regardless of
altitude, which is very useful.
And that means it fits in withour understanding of saturated
(35:53):
vapor, etc.
The caveat to all of that isthat if you know your science
well, you will know that thesaturated vapor pressure of, of
any substance, any liquid orgas, is fixed.
at a specific temperature.
So the only thing that changesSVP is the change in
temperature.
(36:14):
And that does, I believe, haverelevance for us in the
wilderness setting, because ifyou are giving the device to
somebody Outdoors here, perhapsin Crested Butte now where it's
a few degrees below zero Celsiusversus somebody who's just had a
hyena gnaw on their ankle in thefelt in Africa where it might be
30 degrees Celsius, then you aregoing to be delivering a
(36:37):
different Dosage to the patient.
We've got no actual experimentaldata to show how much the dose
varies We don't know what theeffect of holding the device and
in a hand to keep it warm is Andthat's really an area where we
could definitely have some somefurther work.
So altitude no difference.
It will work Temperature youmust anticipate decreasing
(36:59):
efficacy with decreasingtemperature
Patrick (37:03):
I seem to recall, and I looked this up in response to a
listener comment, but I thinkthat the freezing temperature of
the actual methoxyfluorineliquid is quite low, and perhaps
not clinically relevant here,but it did occur to me that that
problem with the vapor pressure,right, regardless of altitude,
at a colder temperature, you'regoing to produce less vapor from
(37:24):
that wick.
And the same question came tome, which was, okay, if you hold
it and warm it, could youachieve a reasonable dose yet?
The error that's being drawnacross it remains your
environmental air temperature.
So I don't know if it would beat all meaningful to to sort of
cuddle it with your hands andprotect it from the environment
(37:46):
or if that's just a pointlessexercise.
It sounds like there's abudding.
Research project here for anywilderness medicine fellows out
there who
Ross Hofmeyr (37:56):
Absolutely.
Patrick (37:56):
to write a grant and get some funding.
Ross Hofmeyr (37:59):
Absolutely.
As as my as my mentor, MikeJames would say this is an area
of opinion as yet unsullied byevidence
Patrick (38:08):
um, do you have any personal experience using it in
the cold
Ross Hofmeyr (38:12):
on myself, on patients.
Patrick (38:15):
either?
Ross Hofmeyr (38:16):
So yes, we have used it in cold environments.
and I've used it in I'm going tohave to estimate that what the
ambient temperature would havebeen probably would have been
between about minus two andminus five Celsius.
I apologize.
The American listeners that I'mnot fluent in Fahrenheit.
In the snow on a mountainside.
(38:38):
And the patient did describe aGood analgesic effect.
They did describe the sideeffects of the, of, of the
dizziness well lightheadednessrather let's call it.
So it was clear that the, thatthe drug was working whether it
would work in minus 10, minus20, I don't know, but we've used
it outdoors we've used it incold environments and it has
worked.
Patrick (38:59):
I think that in freedom units, that would be around,
like, 20 to 25 degreesFahrenheit.
When you are carrying it, do youkeep it close to your body if
you are in a colder environment?
Or do you attempt to keep itisolated from the elements?
Or is it just in your pack withyour other Okay,
Ross Hofmeyr (39:31):
that goes inside my jacket to prevent it from
freezing.
As, as you said, the freezingpoint of methoxyfurane is well
below zero Celsius, so actualfreezing of the agent is is not
really an issue.
And I think The con the, theissue really is how cold does it
get in that vaporization chamberand you know, will, will it
vaporize efficiently foranalgesic effect?
And I don't know the answer tothat question when we're
(39:53):
talking, you know, deep Sub-Zerotemperatures.
Patrick (39:57):
it really sounds like it's a, it's quite an ideal
medication for that the prehospital environment because it
requires such Little access,it's so easy to use, it's
titrated by the patient.
Are there downsides that you seeto it?
Ross Hofmeyr (40:13):
So the first one that comes to mind particularly,
you know, coming from an Africansetting is, is cost.
In.
In my South African rands, amethoxyfluorine combo kit with
the inhaler and two vials isprobably around a thousand times
more expensive than a, than anampoule of morphine which, you
(40:34):
know, in our, in our governmenthospital practice costs next to
nothing.
So, you know, the cost, the costis definitely higher.
There's a theoretical downsidein terms of environmental
contamination, and I mean, youknow, the greater global
environment although the amountof methoxy that we use in the
environmental dwell time ofmethoxy makes it a fraction of
(40:56):
the risk of you know, othergreenhouse gases like nitrous
oxide.
Another small downside isalthough the, the delivery
device itself is very light, itis somewhat bulky to carry.
So you could carry a couple ofsyringes and multiple ampules of
you know, opiates and otherthings for the bulk that you
need to, to carry in Methoxycombo kit on the plus side, they
(41:17):
are, they're very, very robust.
You know, they can get kickedaround and thrown around in a
pack.
The, the little ampule itself isvery, very tough.
So it doesn't get, I mean, I'venever.
Broken one accidentally evenwhen, you know, dropping packs
out of vehicles, other thingslike that other downsides, not,
not a whole lot.
I mean, it becomes another thingthat you have to carry another
(41:38):
thing that you have to disposeof.
I tend to throw mine in theplastic recycling, and that's
the end of that.
Patrick (41:44):
Okay.
Very good.
Well, I appreciate you takingthe time to discuss this with
me.
And for us, it's been funwatching the.
Sunset behind you in Colorado asI'm here in Hawaii where the sun
is definitely still up thanksfor for making the time to join
us on for For future episodes.
You're a wealth of knowledge
Ross Hofmeyr (42:06):
Well, thanks very much, Patrick.
And yeah, if I can encourage thelisteners that if they haven't
gone and had a look at the WMSacute pain practice guidelines
for which Patrick is the thelead author and really lit the
fire under all of us to get thatdone, then that, that those
guidelines are a really, reallygreat resource.
And yeah.
If you're going to read onething after listening to this
(42:28):
conversation, then open up theWMS CPG.
They're free.
They're online.
And if anyone does want to lookme up and reach out for more
information, I've got quite alot of stuff that you know, I
can send out to people.
My email is easy.
It's Ross at wild medics with anX.
com.
Podcast description.
Patrick (42:49):
Yeah, we'll put links to everything I can find about
you down there, Ross, so thatyou can be bothered to no end by
our listeners.
Ross Hofmeyr (42:58):
Fantastic.
Thank you.
Patrick (43:00):
And that's a wrap on my conversation with Dr.
Hoffmeier.
Thanks again, Ross, for joiningus on the show.
I really appreciate the time andthe expertise, and I hope that
everyone listening out therelearned something.
At times Ross gets deep.
I hope that everyone out therefound something that they can
take away or found someinspiration.
(43:23):
It's always great to learn more,expand our boundaries, expand
the toolkits that we haveavailable to us for managing
pain in austere environments.
As I mentioned with Ross, all ofthe links can be found down in
the show notes, includingpictures of the green whistle
and links so that you canconnect with Ross and his
(43:46):
company, Wild Medics, if you'reinterested to do so.
As I mentioned in theintroduction, thanks so much to
Eddie and Aaron for thequestions that created this
episode.
And I would encourage all of youto continue to reach out.
It's wildernessmedicineupdatesat gmail.
com, even if you just want tosay, Hey, give a shout out, or
(44:06):
if you have specific questions,things that we can dive into
more, because if you have aquestion, other people have a
question and there's no suchthing as stupid questions here.
We can always take it to thatnext deeper level.
I'm still not on any socialmedia because I just can't
handle that, but I do appreciateit.
(44:26):
If you give the show a rankingor a review on iTunes or
Spotify, that helps this showget out to reach more listeners.
As I've mentioned before, thisis a passion project.
I'm not making money on it.
I am losing money on it, but Ienjoy bringing this content to
you guys and hearing back thatit is delivering value.
To you.
So thank you for listening.
(44:46):
And as always, another way youcan support the show is to share
this episode with someone youthink might appreciate it, or
maybe they want to hear aboutavalanche physiology or how to
make tourniquets out of spaceblankets that episode you think
they might appreciate.
Share it with your fellow nurse,doctor, paramedic, medical
student, nursing student, SARmember, or fellow
(45:09):
recreationalist who just wantsto learn more and be prepared
for those situations in theoutdoors.
Until next time, stay fit, stayfocused and have fun.
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