altitude sickness FYI
BillOldMan
that he thought that Tums, or some other source of carbonates could stave
off mild altitude sickness (headaches, mild nausea), since they could help
supply carbonate ions to balance the loss of carbonate balance due to
overbreathing, which causes too much CO2 to be lost... he used to guide
elk hunters at 13000 ft or so and supplied them with Tums to relieve mild
symptoms. A placebo effect or has there been some study on this treatment?
Anthony R Bubb
>I had a Physiology teacher (not currently a research physiologist) state
>that he thought that Tums, or some other source of carbonates could stave
>off mild altitude sickness (headaches, mild nausea), since they could help
I don't know what drives the effect, but I know that this is an old Mteers
trick, and have buddies that swear by it.
-T.
GregKCra
(BillOldMan) writes:
i've run into climbers in mexico and argentina that used tums for that
reason. whether it works or not ,i don't know.
gregg
william hunt
I talked to 2 knowledgeable people on this subject and they think Tums
would only make AMS worse. They are checking into though.
Willie Hunt
BillOldMan
overbreathing at altitude, from exertion or other causes, results in loss
of CO2, which results in loss of carbonic acid (H2CO3) which normally
causes the acid shift in blood that stimulates nerves in the central
nervous system which stimulate breathing, but the body needs O2 and begins
to compensate for the loss of CO3 by providing CO3 ions from other
sources, and runs low, short term, so tums help balance things out, short
term. Seems as though low carbonic acid should result in alkalosis, and
that adding an antacid should make things worse, but it's the carbonate
ions that are lost and that are replaced by tums. I think dehydration is a
bigger threat, but I've never run into serious problems, being a more or
less a moderate mountaineer.
Tom Bunch
That's the hypothesis, more or less, but it's been been pretty
conclusively debunked. Another important part of the theory is that
the phenomnae noted above trigger vasodilation in the brain (maybe
elsewhere too -- I'm a lay person) which can lead to hypoxic brain
damage.
I decided it was silly to live with all the misinformation on the
Rolaids thing, so I gave Tom Hornbein a buzz, since his office is
quite near mine. Dr. Hornbein was interviewed in the most recent in
R&I in the article by Alan Fitch. He's one of the foremost researches
on all this rot. Any errors this post may (is likely to) contain are
mine. Anything particuarly clever is probably his.
The skinny is this: the Rolaids idea came from Larry Penberthy, then
owner and president of MSR. This was his new idea, after his
suggestion of superdoses of the watersoluble vitamins fell from favor.
Rob Roach, who was at the time a grad student at Evergreen (here in
Washington state) did a controlled study of aluminum hydroxide sodium
carbonate versus (Rolaids) on Mt. Rainier and found, as a majority of
respectable scientists predicted, no benefit. Hornbein wrote a
critique of Penberthy's unconventional interpretation of the
scientific method, and Penberthy wrote irate letters to the Dean of
the medical school and the President of U. Washington, then Charles
Oderguard. The critique was published in one of the climbing rags,
maybe _Summit_ or _Climbing_. I wish I could tell you more specifically,
but I can't. Doc Hornbein had considered this history more or less
successfully repressed until I brought it up. He was openly shocked
at the idea that anyone was still recommending Rolaids to stave off
AMS. After Larry Penberthy gave up on all this, he made an abortive
bid for U.S. Senate, which is, I suppose, totally irrelevant.
Now I'm going to go farther out on a limb and try to describe what
Diamox is all about. Diamox is a carbonic anhydrase inhibitor.
Carbonic anhydrase (henceforth C.A.) is an enzyme carried around
mostly by red blood cells which aids carbon-dioxide transport from the
tissues and its release from the blood in the lungs by catalyzing the
reversible hydration of carbon dioxide to carbonic acid. Vastly
simplified, the body produces lots of h2co3 (bicarbonate) when sugars
are used, and C.A. is a catalyst as it goes to h+ and hco3- (hydronium
ion and carbonic acid) and from there to h20 and c02. Inhibitting
C.A. merely slows down this reaction. I'm still a little mystified by
the intricacies of it -- intuitively, how can you correct an imbalance
by inhibitting the enzyme the body uses to readjust that balance? But
my understanding is that hyperventilation causes you to blow off an
excess of co2, resulting in acidosis which can lead to cerebral edema.
But if co2 is not so readily available to be blown off, it's just
retained as carbonic acid or bicarbonate. Apparently, loading up with
that dross doesn't inhibit absorbtion of o2. Bicarbonate, by the way,
is the most important PH buffering agent in our bodies. Also, bear in
mind that some of this stuff is still just theory. For example, it's
still debatable that acidosis -> vasoconstriction in the brain ->
hypoxic brain damage and cerebral edema. Another thing Dr. Hornbein
went into was that inhibitting C.A. raised the difference in partial
pressure of CO2 between, I think, arteries and capillaries, which in
turn keeps the CO2 out in the tissue instead of in the blood where it
will have to be dealt with. My understanding of this last bit is
minimal, and I didn't want to keep him busy too long answering dopey
questions.
Anyway, given all the above, it's not surprising that people might
think Rolaids might help -- it's full of carbonate. The fact is, it
only helps with indigestion and such.
One controlled study (again, I can't cite it specifically) got results
something like this with Diamox:
incidence of headache
patients with nothing 70%
patients with placebo 50%
patients on Diamox 7%
This was on a two day climb of Mt. Rainier (14,410 ft). It's
generally accepted that headaches and nausea are at one end of the
spectrum that leads to cerebral edema. Whether the mechanisms are
approximately the same for pulminary edema is a matter of less
concensus.
An alternative drug is Decadon (sp?), a steroid. There has been no
comparing study between the two so far as Dr. Hornbein knows. I
should think, given the prevalence of Diamox, that Decadron is only of
interest to patients for whom Diamox is contraindicated, such as those
with acute narrow angle glaucoma (rare form of glaucoma).
Effectiveness of Diamox has been shown to vary quite significantly
between individuals. Basically, you want to ask your doctor about it,
but most prescribe 250mg two or three times per day. Many believe
that once per day is enough, but once you've found what works, you
tend to stick with it. If you take what is, for you, a large dose,
you will get tingly sensations in your extremities. If it's not
uncomfortable, fine. But it can apparently make you feel "really
weird". If so, you should (again, ask the prescribing doctor) be ok
to cut your dosage in half.
I tried to look up a few specific citations just now, but apparently
the database is down. Isn't it great having computers to blame for
things?
-Tom Bunch
P.S. If we're lucky T.H. himself may come around and clarify this
further for us -- I pointed him in the general direction of
rec.climbing. Now, if he can suffer all the slings and arrows,
perhaps we'll see his face here.
David Ress
Bunch) wrote:
>Now I'm going to go farther out on a limb and try to describe what
>Diamox is all about. Diamox is a carbonic anhydrase inhibitor.
>Carbonic anhydrase (henceforth C.A.) is an enzyme carried around
>mostly by red blood cells which aids carbon-dioxide transport from the
>tissues and its release from the blood in the lungs by catalyzing the
>reversible hydration of carbon dioxide to carbonic acid. Vastly
>my understanding is that hyperventilation causes you to blow off an
>excess of co2, resulting in acidosis which can lead to cerebral edema.
>But if co2 is not so readily available to be blown off, it's just
>retained as carbonic acid or bicarbonate. Apparently, loading up with
>that dross doesn't inhibit absorbtion of o2. Bicarbonate, by the way,
>is the most important PH buffering agent in our bodies. Also, bear in
>mind that some of this stuff is still just theory. For example, it's
>still debatable that acidosis -> vasoconstriction in the brain ->
>hypoxic brain damage and cerebral edema.
>
From what I've been able to piece together from various mountaineering
medicine lectures, the altitude problem starts with low oxygen. Less oxygen
means lower blood oxygenation resulting in a slow down in aerobic cell
metabolism. Reduced metabolism results in LESS CO2 output from the cells
into the blood stream. Unfortunately, the body still tries to blow off the
CO2 at the same old sea-level rate, so the carbonic acid level in the blood
drops and you have alkalosis. Your body responds to this by peeing off extra
water (diuresis), presumably to get the acidity back up again. The maladies
of alitude sickness are associated with this response to alkalosis.
It seems reasonable that Diamox would help ease this problem by reducing the
rate at which CO2 is removed from the blood stream, avoiding the alkalosis
problem in the first place.
Is there a sports physiologist on the net to set us straight?
--------------------------------------------------
David Ress
Laser Experiments and Advanced Diagnostics Group
Re...@llnl.gov
Tom Bunch
because I didn't really understand how they worked, and I didn't want
to spread still more misinformation on the whole topic, but in
retrospect, I'm afraid people might assume I've told the whole story.
Fortunately, Allen Sanderson (al...@doug.med.utah.edu) took the time
to fill in the blanks for me, and point out one or two other things.
I will include the relevant bits of his letter (with permission).
Also I remember reading a post here about an alternative drug in
testing, but I couldn't remember any specifics. The post turns out to
have been by Denzil Boradhurst regarding bnezolomide, and I will
append it as well. This info may never, sadly, become useful since,
as Denzil points out, it does not seem to have a profitable market and
so probably won't be produced.
-Tom
--
From: Allen Sanderson
Diamox is a trademark name for acetazolamide.
You are almost correct in what an acetazolamide does. It is an
ihibitor, but not quite everywhere you mention in the chemical
reation. [I'm sure this is what he meant, but actually it inhibits
production of the enzyme that catalyzes the reaction, which amounts
to the same thing. -Tom]
Bicarbonate reduces down to hydronium and carbonite acid. Carbonic
anhydrase comes into play in breaking down the carbonic acid into
water and carbon dioxide which is expelled through your renal system
(kidneys) and repitory system (lungs), respectively.
You kinda implied that cardonic anhydrase helps break down bicarbonate
which it does not - it only affects the second reaction. [This
contradicts what was told to me by a physician, but Allen may be
right -- this physician emphasized that he was not current on this
stuff. -Tom]
Now when you take acetazolamide it inhibits the break down of carbonic
acid into water and carbon dioxide. Thus it makes your blood acidic
(ie brings on acidosis) because there is too much carbonic acid in the
blood. Your body reacts in two ways. First, it tries to bring in
more oxygen so a pH balance is maintianed between oxygen and the
carbonic acid which is what we want. But at the same time your body
tries to dump the extra carbonic acid (and other good elecrolytes and
water that you really want to keep) through the renal system, not what
we want.
So you end up breathing more, slight hyperventilation, and you piss
like a race horse. So as you can see it does help but at a price.
--
From: denz...@oldham.gpsemi.com (Denzil Broadhurst)
Date: Wed, 26 Oct 94 10:14:54 GMT
Just returned from the British Medical Expedition to Everest - great time,
though I wasn't one of the people climbing Everest, just some of the
trekking peaks (20,000-21,000 ft).
One of the medical trials was a double blind test on Benzolomide to see if it
had the same effects for acclimatisation as Acetazolomide (Diamox). Provisional
results show it to be just as effective, and with fewer side effects. You
still get the tingles in extremities, (including one area where the ladies
wouldn't suffer from!) but it doesn't seem to affect the mental
state like Diamox.
Now for the bad news! The drug was manufactured in the 60's as a possible
replacement for Diamox in treatment of Glaucoma - but it didn't work. No more
has been made and we've just used up the world stocks in the trial!
Anyone out there working for a drugs company prepared to make some more (and
put it through the necessary safety trials - shouldn't cost more than a couple
of million!)?
The doctor in charge of the trial will be publishing his finding and talking
to various Pharmaceutical companies, but if its only application is AMS it is
likely that there wouldn't be sufficient demand to justify the investment.
Shame really, one of the guys with me had problems 15 years back with AMS when
he went to Everest base camp, this time on the trial he got up to 21,000 ft
with no problems.
Denzil