High Altitude Sickness

High Altitude Medical Notes for Trekkers, Leaders & Doctors- By Dr Jim Duff

Note: these notes are not a substitute for expert advice. The author has made every effort to ensure that the information given is as accurate and up-to-date as possible. However, he is unable to accept responsibility for any loss, injury or inconvenience sustained by any person, caused by errors and omissions, or as a result of the advice and information given here.
As we ascend to higher altitudes, our bodies have to acclimatize to the decreasing amount of oxygen available. Failure to acclimatize, often due to ascending too rapidly to 2000m/6560ft or above, results in symptoms of altitude illness (also called high-altitude illness). These symptoms become common above 2500m/8200ft and present in the following ways:

Acute Mountain Sickness (AMS) is the most common and is not life-threatening
HACE (High Altitude Cerebral Edema) is a life-threatening illness that usually develops from AMS
HAPE (High Altitude Pulmonary Edema) is a life-threatening illness; it may occur on its own, or with AMS or HACE These three presentations of altitude illness can vary from mild to severe. Note: Altitude illness, hypothermia and dehydration often occur together; check for these conditions and treat accordingly.

Preventing AMS, HACE and HAPE

Gain altitude slowly. As a rough guide, above 2500m/8200ft, the maximum height gain between sleeping altitudes should not exceed 300m/1000ft per day, with a rest day for every 1000m/3300ft of ascent or every third day. Only ascend when there are no symptoms of AMS

Avoid over-exertion and avoid getting out of breath while acclimatizing, especially if experiencing symptoms of AMS

Drink enough liquid to keep your urine pale and plentiful (an increased urine output after an ascent is a good sign while a decreased urine output indicates that altitude illness is developing)

Avoid alcohol, caffeine, excess salt and too much protein; ideally your diet should be 70% carbohydrate above 3500m/11500ft)

Use the 'buddy system' to keep an eye on each other for symptoms of AMS

Avoid medications that depress respiration (e.g. sleeping tablets, sedatives, strong painkillers and antihistamines) as these increases the risk of AMS. If you must take any of these medications, take Diamox TM as well

If you must fly or drive rapidly to 2500m/8200ft or higher, spend a minimum of two nights at your arrival altitude (or lower if possible) or till symptoms disappear, before ascending. If ascending rapidly to 3000m/10000ft or higher, consider using DiamoxTM (125 to 250 mg 12-hourly, start at least one day before your initial ascent and continue for at least 3 days after arrival). Diamox helps acclimatization and will not mask the symptoms of AMS

Acute Mountain Sickness (AMS)

AMS is common; depending on the altitude gained and the speed of ascent, incidence ranges from 20 to 80%. Typically symptoms appear anytime during the first 36 hours after an ascent. If you rest at the same altitude, symptoms usually disappear quickly (but this can take up to 4 days) and you are now acclimatized to this altitude. AMS may reappear as you ascend higher still, and acclimatization has to occur again.
Symptoms are due to fluid accumulation in brain tissue and vary from mild to severe; it can progress to HACE if it is ignored. People often blame cold-heat-infection-alcohol-insomnia

exercise-unfitness-migraine for their AMS symptoms and carry on up. To continue ascending with symptoms of AMS is dangerous and has led to many deaths.
NB. It may be quite difficult to tell if a young child is developing AMS. The only symptoms may be increased fussiness, crying, loss of interest or loss of appetite.

Symptoms & signs

Headache (typically throbbing, often worse for bending over or lying down), PLUS one or more of the following symptoms:
Tiredness, lassitude
Dizziness, light headedness
Nausea (or vomiting)
Loss of appetite
Insomnia, disturbed sleep, frequent waking

Treatment

Rest (avoid even the slightest exertion if this is possible) at the same (or lower) altitude until the symptoms clear (up to 4 days)
Drink enough to keep your urine pale and plentiful
Use ibuprofen or paracetamol for headache
Consider DiamoxTM (125 to 250 mg 12-hourly) for 3 days, or for the. rest of the time at altitude if symptoms return
Consider Stemeti TM (or other anti-vomiting medication) for persistent nausea/vomiting
If AMS symptoms are severe, give oxygen (1 to 2 L/min) OR use a pressure bag until symptoms clear
Check the victim regularly for signs of HAPE and HACE, especially during the night .
Descend far enough to clear symptoms (at least 500m/1700ft) if symptoms of AMS do not improve or get worse.

Facts on HAPE & HACE

HACE or HAPE occur in approximately 1 to 2% of people going to high altitude HACE and HAPE may occur alone or together
HACE usually develops after symptoms of AMS have appeared and often gets rapidly worse during the night
HACE may develop in the later stages of HAPE
HAPE is roughly twice as common as HACE
HAPE causes many more deaths than HACE
HAPE may appear without any preceding symptoms of AMS
HAPE is more likely in people with colds or chest infections
HAPE often comes on after the second night spent at a higher altitude
HAPE can develop even after descending from a higher altitude

HACE (High Altitude Cerebral Edema)

Symptoms of HACE are caused by an accumulation of fluid in or around the brain. Typically symptoms and signs of AMS become worse and HACE develops. Someone with HAPE may also develop HACE.

Symptoms & signs

Severe headache, which often feels worse on lying down and is not relieved by ibuprofen, paracetamol or aspirin
Tiredness, severe fatigue
Nausea and/or vomiting which may be severe and persistent
Loss of coordination, clumsiness. The victim needs help with simple tasks such as tying their shoelaces or packing their bag. They cannot do the finger-nose test
Staggering, falling. They cannot do the heel-to-toe walking test or the standing test.
Blurred or double vision, seeing haloes around objects
Loss of mental abilities such as memory. They cannot do a simple mental arithmetic test
Confusion, hallucinations
Change in behavior (aggression, apathy, etc.)
Drowsiness, difficult to wake up, coma, death

Tests for HACE

Heel-to-toe walking test: The victim is asked to take 10 very small steps, placing the heel of one foot to the toes of the other foot as they go. Reasonably flat ground is necessary and the victim should not be helped
Standing test: The victim stands with eyes closed, feet together and arms by their sides
Finger-nose test: With eyes closed, the victim repeatedly and rapidly alternates between touching the tip of their nose with an index finger then extending this arm to point into the distance (a useful test if the victim is in a sleeping bag)
Mental arithmetic test: Give the victim a mental arithmetic test, ego subtract 7 from 100, 7 from 93, and so on (but remember some people may be poor at arithmetic even at sea level)

If the victim cannot do any of the above tests easily (or refuses to cooperate), or show excess wobbling or falling over in the two first tests (be prepared to catch the victim if they fall over!), assume they are suffering from HACE. If in doubt about the victim's performance, compare with a healthy individual. Be prepared to keep repeating these tests.

Treatment

Descend immediately (prompt descent will begin to reverse the symptoms). Descend as low as possible, at least 1000m/3300 ft. Descend at night or in bad weather if necessary. Carry the victim if possible, as the exertion of walking can make the illness worse
If descent is not immediately possible (e.g. dangerous terrain or weather, not enough helpers or while waiting for a helicopter), oxygen or the use of a PAC and appropriate medications will keep the person alive until descent can be undertaken
Give oxygen:
- From a bottle using a mask (2 to 4 L/min), OR
- By using a pressure bag (this is roughly the equivalent of 2 to 4 L of oxygen/min) NB: If both oxygen and a pressure bag are available, give the oxygen while the bag is being prepared and after the victim comes out of the bag. Do not give oxygen inside the bag unless it is designed for this purpose and you have been trained to do so.
Give medications:
-8 mg of dexamethasone at once (by mouth, IV or 1M) followed by 4 mg 6-hourly. Dexamethasone takes several hours to work. Stop by tailing off the dose slowly (give the last 3 doses 12-hourly) it once below 2500m/8200ft AND after at least 3 days of treatment
- DiamoxTM 250 mg 8 t012-hourly
- Treat persistent vomiting with anti-vomiting medication
Prop the victim up in a semi-reclining position as lying down flat may make their condition worse
Avoid even the slightest exertion if this is possible. Even walking a few steps may make their symptoms worse or reappear. Do not leave the victim alone
If a person is turning blue or is falling into unconsciousness, give them rescue breathing before they stop breathing

HAPE (High Altitude Pulmonary Edema)

Symptoms of HAPE are due to the accumulation of fluid in or around the lungs. It may appear on its own without any preceding symptoms of AMS (this happens in about 50% of cases) or it may develop at the same time as AMS. HAPE can easily be mistaken for a chest infection or asthma: if in doubt treat for both.

Symptoms & signs

A reduction in physical performance (tiredness, fatigue) and a dry cough are often the earliest signs that HAPE is developing
Breathlessness: in the early stages of HAPE, this may mean just taking a bit longer to get one's breath back on resting after mild exercise. Later on, there is marked breathlessness with mild exercise. Finally, breathlessness occurs at rest. Record the resting respiratory rate (NB: At 6000m/20000ft, normal acclimatized respiration rate is up to 20 breaths per minute)
The dry cough may later become wet with frothy sputum, which may be bloodstained (pink or rust coloured). This is a serious sign
"Wet" sounds in the lungs when breathing in deeply (place your ear on the bare skin of the victim's back below the shoulder blades; compare with a healthy person). Note: There may be NO wet sounds in even quite severe HAPE: this is called 'dry HAPE'
There may be: fever up to 38.5°C, a sense of inner cold, pains in the chest
Blueness or darkness of face, lips, tongue or nails due to lack of oxygen in the blood (cyanosis)
Drowsiness, difficulty waking up, coma, death

Treatment

Same general treatment as for HACE, EXCEPT:

Give oxygen as for HACE but give the bottled oxygen at a rate of 4 to 6 L/min till recovering, then 2 to 4 L/min
Give medications:
- Nifedipine. This should only be used if bottled oxygen or a pressure chamber is not available and the victim is warm and well hydrated. Give the modified release (MR) form of the tablets (20 mg 12-hourly for 2 or 3 days). If a fall in blood pressure occurs due to nifedipine (pallor, weak rapid pulse, dizzy on standing), treat as shock
- DiamoxTM 250 mg 8 to 12-hourly
- An asthma reliever spray (2 puffs 4-hourly) may help

Going back up again?

Anyone seriously ill with HACE or HAPE and needing oxygen, treatment in a pressure bag or dexamethasone/nifedipine, should descend immediately after treatment. As, even if they feel completely recovered, symptoms may rapidly rebound with exertion or further ascent.
Having descended and having become symptom-free at a lower altitude, they should not go up again as it is highly likely that the HACE or HAPE will reoccur (rebound)
If re-ascent is unavoidable (eg. driving out of Tibet over high passes), give DiamoxTM 250 mg 12-hourly. If the original problem was HACE, add dexamethasone (4 mg 12hourly); if the problem was HAPE, add modified release Nifedipine (20 mg 12-hourly). Give oxygen while crossing passes

Periodic (Cheyne Stokes) breathing

This unpleasant condition occurs while sleeping at altitude. If someone suffers from it, always check them for symptoms of altitude illness.

Symptoms & signs

Short periods of normal or fast breathing followed by breath holding then several gasping breaths. This can be quite frightening for the victim's buddy
The victim often wakes feeling like they are suffocating
Sleep is disturbed and of poor quality

Treatment

Give Diamox, 'the high altitude sleeping pill', 125-250 mg at night or 12-hourly.

Notes on acetazolamide (DiamoxTM)

This is a mild diuretic, which acidifies the blood thus improving respiration and acclimatization. There are three reasons for using DiamoxTM: prevention of AMS, treatment of AMS, and for sleeping difficulties.

Prevention of AMS

There is good evidence that Diamox TM is effective for preventing AMS. However, routine preventative use for all trekkers on all treks is NOT recommended.
Preventative use is recommended for those who have a past history of Altitude Illness, or when rapid height gain is unavoidable.
Here are some examples of situations where gradual height gain is not possible:

Any ascent of Kilimanjaro under 10 days, in which case use Diamox TM 125 mg twice daily from the start of the ascent till back below 2500 m (8200 ft).
Flying or driving rapidly to altitude (e.g. Lhasa, Leh, Cuzco and Jomoson, to name some popular destinations). Consider using DiamoxTM preventively (DiamoxTM 125 mg twice daily, one day before flying and for two or three days after arrival) if the traveller is expecting to be active and carrying on and up straight away, instead of resting for two or three days after arrival. DiamoxTM is NOT needed when flying into Lukla (Everest trek) if two nights are spent below Namche Bazaar.


Treatment of AMS

If someone has symptoms of AMS (even if marginal), it is important that DiamoxTM is started promptly since it offers the best chance of enabling the trekker to continue. (DiamoxTM 125 mg twice daily, double this dose for AMS sufferers who have well-developed symptoms or who do not respond quickly). If the person has a flexible itinerary, there is also the preferable option of resting at the same altitude or even descending to cure the symptoms. This is often not possible on treks with a fixed itinerary and the case for the prompt use of DiamoxTM is much stronger.
AMS symptoms should be treated vigorously at any time but especially at the end of the day. Administer DiamoxTM, rest in a warm environment, rehydrate, give painkillers for headache and Stemetil for nausea or vomiting. A spell in a Portable Altitude Chamber (PAC) or Gamow bag is recommended. Try to abolish symptoms of AMS by active treatment before the person goes to sleep for the night, rather than hoping they will be gone in the morning.
A person with obvious symptoms of AMS that do not disappear should not ascend to sleep at a higher altitude.

Poor sleep

This is a common problem at altitude. First line of treatment for insomnia is check warmth of sleeping bag, decent insulation and advise no caffeine. DiamoxTM, which acts as a respiratory stimulant, is indicated for sleep disturbance at altitude, particularly where this is associated Nith periodic breathing (repeated bouts of stopping breathing followed by gasping breaths).

Some altitude physicians refer to DiamoxTM as 'the high altitude sleeping pill'. The starting dose is DiamoxTM 125mg (half a tablet) an hour before going to bed. (If symptoms persist try 125 mg twice daily. If that doesn't work, try 125 mg in the morning and 250 mg at night).

Diamox; allergy and side-effects

DiamoxTM may cause an allergy in some people. It must be avoided if there is past history of an adverse reaction to DiamoxTM or sulfa containing drugs (eg. SeptrinTM, BactrinTM). Some common side effects of DiamoxTM:

Extra urine output. Worries about this tend to be exaggerated. Keep your urine pale and plentiful. Use a pee bottle (SanifemTM or TupperwareTM box for women), at night in tents or lodges to avoid getting cold or falls while going out to the toilet.
The most obvious side effect is paraesthesia (tingling) in lips, fingers, toes, and a metallic taste when drinking carbonated drinks. Both symptoms are milder with lower doses and disappear on stopping the medication.
DiamoxTM can cause a person to sunburn more easily ('photosensitivity').

A common concern about DiamoxTM is that it will mask the onset of altitude illness. There is no evidence that DiamoxTM masks the onset of AMS, HACE or HAPE. However, DiamoxTM is not guaranteed to work so even if someone is taking DiamoxTM, and AMS, HACE or HAPE may still develop. In which case act accordingly.

Notes on gingko biloba

This herb has been suggested for use instead of DiamoxTM for those with a sulfa allergy (rare) or who prefer the herbal approach. The evidence for its efficacy is much more limited than for DiamoxTM. Recent reports suggest that Ginkgo may precipitate AMS and HACE if started only at the beginning of the trek (the leader/doctor should make their group aware of this). The current recommendation is to start it six weeks before the trek starts. The dose is 80 to 120 mg 12-hourly.

Painkillers at altitude

If pain relief is needed at altitude, paracetamol is the safest option. Ibuprofen is possibly more effective but carries a slightly higher risk of serious side effects. Neither drug will mask symptoms of altitude illness. Anyone starting to take anything but their regular medication must inform the leader/doctor when they do so.