Uiaa mountain medical centre

UIAA Mountain Medical Centre
Information Sheet 1
MOUNTAIN SICKNESS, EDEMAS & TRAVEL TO HIGH ALTITUDES

Introduction
A family of related medical conditions that sometimes develop when people travel to altitudes
above 3500m (11,500ft), at times even lower. There is a wide variation in both the speed of
onset, the severity of symptoms and also at the height at which they occur – this is different
for each person. The problems are caused by lack of oxygen.
Acute Mountain Sickness
Most people feel at least a little unwell if they drive, fly or travel by train from sea level to
3500m. Headache, fatigue, undue breathlessness on exertion, the sensation of the heart
beating forcibly, loss of appetite, nausea, vomiting, dizziness, difficulty sleeping and irregular
breathing during sleep are the common complaints. These are symptoms of Acute Mountain
Sickness (AMS), which usually develop during the first 36 hours at altitude and not
immediately on arrival. Well over 50% of travellers develop some form of AMS at 3500m, but
almost all do so if they ascend rapidly to 5000m (16,400ft).
Acclimatisation
Usually, these unpleasant effects of lack of oxygen wear off over two to three days,
particularly if no further ascent is made. Once the body has acclimatised in this way, further
gradual height gain is possible although symptoms may recur at any time. The question "How
high, how fast?" has no absolute answer because of individual variation, but it is reasonable
for healthy people of any age to travel rapidly to 3500m, though many will develop some
degree of AMS after arrival. It is unwise to travel much above 3500m immediately from sea
level.
Above 3500m, the speed of further height gain should be gradual and we advise no more than
a 300m increase in sleeping altitude per day (with a rest day every third day) and spending at
least a week above 3500m before sleeping at 5000m. This does not mean you can’t ascend
more than 300m in a day (eg. to cross a pass or attempt a summit), as long as you descend
again before sleeping. The highest altitude where man lives permanently is about 5500m
(18,000ft) but on mountaineering expeditions or a trek, residence for several weeks around
6000m (20,000ft) is quite possible and at these altitudes one should feel entirely well when
acclimatised, being limited only by breathlessness on exertion.
Prediction of AMS
There is unfortunately no way of predicting whom AMS will seriously trouble and who will
escape it. It is tempting to suppose that being physically fit and avoiding smoking would help
in prevention but unfortunately, this does not seem to be the case. Similarly, if you have
previously been affected (or not), it seems no more or less likely that you will avoid AMS the
next time you travel to altitude.
Strenuous exercise at altitude, whether or not the subject is fit, makes AMS worse; undue
exertion and heavy loads should therefore be avoided until acclimatised. Patients with heart or
lung disease or high blood pressure should seek specialist advice before travelling above
4000m.

Prevention of AMS: Diamox (acetazolamide)
There has been much research on Diamox, a drug used to reduce fluid retention (it makes
you urinate). There is no doubt that Diamox is genuinely useful in the prevention of Acute
Mountain Sickness if taken for several days before ascent, however it is not without it’s
dangers. If people really want to take this as a prophylactic medication, I usually give 125mg
Diamox twice daily for 3 days before ascent to 3500m (or more), and for two more days - i.e.
five days in all. Exactly how it works is unknown, but its effect on breathing (it makes breathing
faster and deeper in sleep) may be more important than its direct effect on the output of urine.
Travellers who choose to take Diamox should be aware of its unwanted effects - for all drugs
have their dangers. Some people feel nauseated and generally unwell, and tingling of the
fingers is quite common. More unusual side effects include flushing, rashes, thirst, drowsiness
or undue excitement, and occasional serious allergic reactions - although these cease when
the drug is stopped. A test day (or two) of Diamox at sea level well before a trip is sometimes
helpful.
It should be noted that Diamox is not recommended as a routine drug before any ascent:
many mountaineers and trekkers prefer to do without it (I do not usually take it myself). The
important point to understand is that it only relieves the symptoms of AMS and will not
prevent the condition worsening should a sufferer fail to descend or rest. Thus its routine use
to before, or to allow continued or rapid ascent is extremely dangerous, possibly masking
warning signs (symptoms) of more serious HAPE and HACE and allowing ascent to a point
where subsequent descent is difficult or impossible. Diamox should only be used for the relief
of AMS in a controlled fashion, to allow descent and rest - the only cure for AMS.
Prevention of AMS: Hypoxic Training
Over the years there have been various attempts to train in a hypoxic environment – other
than going high, which is obviously the simplest advice. Recently, a hypoxic tent has been
marketed in the US, however we have no information about the efficiency, safety or cost of the
system, and would welcome information from anyone who has used it. For more information,
contact:
Hypoxico Inc
50 Lexington Avenue, Suite 249
New York, NY 10010
Tel: 001-212-726-3654
Fax: 001-212-213-3247


Treatment of AMS
It is important to emphasise that Acute Mountain Sickness, though unpleasant, is usually a
self-limiting condition without serious long-term consequences. Aspirin, Panadol
(paracetamol), or Neurofen help the headache, and drugs used for travel sickness such as
Avomine (promethazine), Stemetil (prochlorperazine) and Stugeron (cinnarizine) may help the
nausea and dizziness. Dexamethasone (a steroid) is also used. Oxygen by mask also helps
the symptoms, as does use of a portable altitude compression (PAC) chamber.
Personally, I tend to use no drugs (apart from oxygen) unless really necessary because the
symptoms usually resolve: the only cure is to rest, become acclimatised to the lack of oxygen
and if necessary descend. The most important treatment is not to go higher if one has
symptoms and to consider losing altitude if either recovery does not take place within several
days - and certainly, if symptoms become steadily worse.
Severe Forms of AMS: High Altitude Pulmonary and Cerebral Edema (HAPE & HACE)
In less than 2% of travellers AMS occurs in several serious forms at 4000-5000m and
occasionally lower. High Altitude Pulmonary Oedema is one, in which fluid accumulates in the
lungs and causes severe illness (which may come on in minutes) recognised by
breathlessness and sometimes a bubbling sound in the chest.
Early pulmonary oedema should be suspected if breathlessness at rest occurs or if someone
has what appears to be a persistent cough or chest infection causing breathlessness. Patients
with pulmonary edema are dangerously ill and should be treated as an emergency and
evacuated to a lower altitude. Frequently a descent of only 500m is sufficient to improve the
situation dramatically. Oxygen by mask is especially helpful, as are PAC chambers,
Nifedipine, Diamox and steroid drugs (see below).
High Altitude Cerebral Edema is another form of AMS, thankfully also a relative rarity. It is due
to fluid collecting within the brain causing the victim to become irrational, drowsy and confused
over a period of hours - their walking will become unsteady and double vision, headaches and
vomiting may occur. Again, the condition is a serious one and evacuation to low altitudes
mandatory. Steroid drugs such as Dexamethasone (Decadron) are used in treatment, in
addition to oxygen and/or a PAC chamber.
In both these conditions, medical advice is desirable though it may well not be available.
Anyone suspected of having pulmonary or cerebral oedema should be evacuated to lower
altitude promptly and should certainly not go high again until a doctor has seen them.
Complete recovery from both conditions is usual if the casualty is treated early and
appropriately.
Peripheral Oedema & Retinal Haemorrhages
Fluid retention causing swelling of the face, an arm or a leg is sometimes noticed on waking or
after a long march - this is peripheral oedema. The condition usually subsides over several
days and does not herald pulmonary or cerebral oedema. Haemorrhages into the retina
(minute blood blisters in the back of the eye) are known to occur quite commonly around
5000m but very rarely cause any problems, being unnoticed by the subject and visible only to
a trained observer with specialist equipment (an ophthalmoscope). Very occasionally, these
tiny haemorrhages interfere with vision (causing a "hole in the vision") – if affected descent is
advised, and complete recovery is usual though not invariable.
Summary
Acute Mountain Sickness is a common and minor, though debilitating problem at high altitude.
Rarely, it leads to two potentially fatal conditions – High Altitude Pulmonary and Cerebral
Oedema (HAPE & HACE) - both of which are medical emergencies.
In giving advice about travel to high altitudes it must be stressed that the simple adage of
gaining height slowly and descending promptly if one is ill - advice known for generations in all
high countries - cannot be bettered. More detailed notes about treatment of all forms of AMS
follow.
TREATMENT OF AMS, PULMONARY AND CEREBRAL OEDEMA

Mild AMS
1.
Drugs for nausea & vomiting (see text - they are often unhelpful) Severe AMS/High Altitude Cerebral Oedema
1.
Dexamethasone 8 mg by mouth followed by 4 mg every 6 hours for 24 hours Diamox (acetazolamide) 125-250mg twice daily for 3 days High Altitude Pulmonary Oedema
1.
Nifedipine 20 mg by mouth + 20 mg every 6 hours for 24 hours Severe Altitude Illness, type unknown
No harm is likely if all treatments are given: NOTE: The potential unwanted side effects of the drugs mentioned above (listed above and in
sheet 3) should be considered before their use.
The UIAA Mountain Medicine Centre is supported by: International Union of Alpine Associations (UIAA)
Dr Charles Clarke FRCP
Updated October 2002
UIAA Mountain Medicine Centre

Source: http://www.hikingintherockies.com/other/UIAA01-MountainSickness.pdf