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Altitude illnesses

There are 3 main illnesses related to high altitude:
acute mountain sicknes (AMS)
high altitude cerebral oedema (HACE)
high altitude pulmonary oedema (HAPE).

HAPE and HACE are potentially fatal if not adequately treated
descent is the most important part of the treatment

Three rules to stop you dying of altitude illness

1. Learn the early symptoms of altitude illnesses and be willing to recognise these.
2. Never ascend to sleep at a higher altitude with any symptoms of altitude ilness.
3. Descend if symtoms are getting worse despite resting at a constant altitude.

High altitude illnesses:


Video showing effects of acute hypoxia:


AMS

The commonest altitude illness - approximately 50% people going to the altitude of Everest base Camp (5300m) would get AMS.
It tends to occur around 3000m.

Definition

In the setting of a recent gain in altitude, the presence of headache and at least one of the following symptoms:
- gastrointestinal (anorexia, nausea or vomiting)
- fatigue or weakness
- dizziness or lightheadedness
- difficulty sleeping


Clinical features

Headache is a common symptom of AMS; other symtpoms, often compared to those of a hangover, include nausea, vomiting and fatigue.
If the casualty develops ataxia (problems with balance when walking) they must be descended; it indicates development of HACE.
The tandem Romberg test can be used - the feet are placed heel to toe (touching) and each hand is placed on the opposite shoulder. When healthy it should be possible to stay in this position with the eyes closed for 30 seconds.

The Lake Louise Score can be used to monitor symptoms from being at altitude & diagnose AMS

This is what ataxia looks like - this trekker has HACE not AMS

Prevention

The best treatment is prevention through gradual ascent: above 3000m do not increase the sleeping altitude by more than 300m/day and after every 3 days have a day where the sleeping altitude is not increased. In the day time ascent above the sleeping altitude can help acclimatisation.
Acetazolamide can be taken to reduce the risk of AMS. It aids acclimatisation but is not without problems; someone considering taking it as prophylaxis should take it at low altitude first to ensure they can tolerate the side effects.

Treatment

Simple pain relief for the headache is often sufficient treatment for AMS, which tends to settle over 2-3 days. Occasionally other symptomatic treatment, such as antiemetics are are used.
Acetazolamide can be used for treatment after symptoms develop.
Ideally one would not sleep higher until the symptoms of AMS have settled. This may not be possible; the patient must be closely observed and if their condition deteriorates while/after ascending the patient must be descended.


HACE = high altitude cerebral edema (US spelling of oedema)

This is swelling of the brain - as bad as it sounds
0.05 % trekkers to EBC develop HACE.
HACE tends to develop at around 4500m.
HACE and (mild) AMS can be viewed as being opposite ends of a spectrum of illness.
HACE is life-threatening.

Prevention

1) Gradual ascent as above for prevention of AMS
2) Following treatment guidelines for AMS - failure to descend a casualty with worsening AMS risks causing HACE

Clinical Features

Any neurological deficit at altitude should be viewed as a manifestation of HACE until proven otherwise.

Treatment

DESCENT (even in the dark/adverse weather unless really impossible)
Keep slightly head up (may reduce ICP)
Oxygen if available
Dexamethasone is the main drug that is used (8mg initially orally or injected)
Acetazolamide is also given
Portable altitude chamber/Gamow bag or similar when descent is not possible.


HAPE = high altitude pulmonary edema

This is fluid collecting in the alveoli - the parts of the lungs that should be full of air to allow oxygenation of the blood
1 - 2 % trekkers to EBC.
Common around 4200m.
Can be fatal, though less so than HACE.
HAPE may develop on background of AMS but can be the first manifestation of altitude illness.

Prevention

Gradual ascent
Salmeterol inhaler (probably) but not salbutamol
For those who have to move rapidly to high altitude (e.g. to effect a rescue) dexamethason can be used for prevention, though this can have side effects and is not recommended for "normal" circumstances.

Clinical Features

Dyspnoea - exertional at first.
Since many people will be breathing fast when trekking at altitude one way to determine who is having problems is the assess the respiratory rate of mambers of the group after a short period of rest - in this time most will return towards normal, but someone with HAPE will remain markedly tachypnoeic.
Cough - may be dry or productive. This may also be due to "Khumbu cough" (a high altitude cough due to cold dry air) which is irritating and uncomfortable (and may lead to rib fractures) but a cough at altitude should initially be assumed to be HAPE until proven otherwise.

Prevention

In those who have hd HAPE before oral nifedipine and/or inhaled salmeterol (not salbutamol) may be useful drugs to reduce the risk of further HAPE but the best way to minimuse the risk is to acclimatise according to standard advice and to avoid over-exertion.
For those who have to move rapidly to high altitude (e.g. to effect a rescue) dexamethason can be used for prevention, though this can have side effects and is not recommended for "normal" circumstances.

Treatment

DESCENT (even in the dark/adverse weather unless really impossible)
Sit casualty up
Oxygen if available
Nifedpidine is the traditional drug used to treat HAPE - 10mg capsule pricked several times chewed and swallowed with this repeated after 15 minutes providing the BP does not frop too far, and 30 minutes after the frst dose (again assuming the BP is OK) give 20mg of the MR preparation. Repeat the 20mg dose every 6 hours.
Sildenafil (viagra) has been used with excellent results
Acetazolamide is given if available
Loop diuretics do not really help in HAPE


PAC (portable altitude chamber) being used to treat HAPE on Mount Kilimanjaro:
gamow_low_res.jpg

Use of the PAC:

(good video though I'd prefer the term "casualty" rather than "victim")

Acclimatisation

As altitude increases the oxygen available in the atmosphere decreases. Sudden exposure to the hypobaric hypoxaemia that is found at altitudes of several thousand metres results in death. Acclimatisation is the response of the body to gradual exposure to increasing altitude.
Responses to high altitude include:
  • Increased ventilation (both rate and depth) (though respiration may decrease during sleep)
  • Increased heart rate
  • Increased volume of urine


Links

AMS
High altitude illnesses

Recommended books

Altitude Illness: prevention & treatment
Travel at high altitude (Medex)