Altitude sickness prevention: Travel Health: NEVDGP

Information mostly taken from: "International Travel and Health" (WHO year book - internet only)
Australian Immunisation Handbook, 8th Edition - 9/2003 - Part1 - Part 2 & Part 3 (large pdf files)
Centre for Disease Control, USA - www.cdc.gov/travel Travel Health Seminar Oct 96, June 97,Feb 98, March 99, May 2000, August 2002 & March 2005 - Victorian Medical Postgraduate Foundation.
Manual of Travel Medicine, Melbourne, Oct 2004. Updated 06/09/2006. Additional references & disclaimer.

AMS (Acute Mountain Sickness)
WHAT IS IT?
Most people who ascend rapidly to heights above 2500 metres (8200 ft) have a period of unpleasant acclimatisation. During this time they may have a variety of symptoms, the most prominent of which are headache, lassitude, insomnia, loss of appetite, nausea and vomiting. These symptoms are collectively referred to as acute mountain sickness (AMS). Acute mountain sickness is a preventable and potentially serious disease. Travellers to the Himalayas, Tibet, Nepal, the Andes, Mount Kilimanjaro and Mount Kenya, or the Rocky Mountains should be aware of AMS.

HOW AND WHEN DOES IT OCCUR?
Acute mountain sickness is infrequent below 2500 m. It occurs in travellers who rapidly ascend to altitudes of 2500 m or more; travellers who drive, ride or fly to high altitude sites in the Andes and the Himalayas are more at risk than those who walk in. The risk relates more to the speed of ascent than the altitude reached. The problem is caused by the reduction in atmospheric pressure with altitude. Less oxygen reaches the muscles and the brain, and the heart and lungs must work harder to compensate. Individual susceptibility to acute mountain sickness is highly variable, and males are more susceptible than females. Youth and fitness do not prevent AMS. see also Children & altitude

WHAT ARE THE SYMPTOMS?
AMS develops over a few hours to a few days usually during the first 1-2 days at high altitude. In rare cases AMS may be delayed by as long as 3 weeks.

Mild form of AMS: Symptoms include headache, dizziness, fatigue, loss of appetite, nausea, and a general feeling of being unwell that is often compared to having the flu or a hangover.
The symptoms of mild AMS are an important warning and should not be ignored.
Nb. The use of sleeping tablets and alcohol can aggravate AMS

Severe AMS: It may develop from mild AMS or it may begin with little or no warning. There are 2 types of severe AMS-high altitude pulmonary oedema "HAPE" (fluid in the lungs) and high altitude cerebral oedema (swelling of the brain). They may occur independently, but usually both forms occur together. The symptoms may include severe headache, vomiting, severe lassitude, drowsiness, giddiness, stumbling, inability to sit upright, shortness of breath at rest, cyanosis (blue' nails and lips), cough and white or pink frothy sputum. It is important to remember that people with AMS are a risk to themselves as well as others, are more likely to fall or have other injuries and be belligerent, irrational and irresponsible. (Refusing to descend to a lower altitude). A simple daily test of a persons ability to walk a straight line will often detect early cases.

HOW CAN ACUTE MOUNTAIN SICKNESS BE PREVENTED?
The most effective preventive measure to avoid AMS is gradual acclimatisation and slow ascent. The altitude at which the climber sleeps is the most important factor: climb high but sleep low. Once above 3000 m particular care should be taken not to increase the sleeping altitude by more than 300 metres per day, and to spend an extra day for each 1000 m gained. For trekking above 3500 m it is advisable that you travel with an experienced leader or guide. Treks organised by good professionals are planned so that you acclimatise on the approach route.
Recently the use of a high carbohydrate diet prior to acclimatisation has been recommended.
Those who fly to high altitude must be prepared to spend time acclimatising on arrival. The body's water losses increase during an active day in the dry cold air at high altitude, therefore, fluid intake should be increased (you may need as much as 4-7 litres per day).
Drugs to prevent AMS often only hide the warning symptoms. In general it is much safer to rely on good planning and gradual ascent rather than medication
However drugs may be useful in selected individuals, such as those known to be at risk of AMS, and those flying to altitude (eg Le Paz in Bolivia is 3600 metres), for a rescue or some other critical task.

Acetazolamide (Diamox) Diamox 250 mg tablets(1/4 up to 1 tablet) given twice a day commencing one or 2 days before the ascent to altitude above 2500 m and continued for at least 5 days at the higher altitude hastens the acclimatisation process and decreases the frequency of AMS by about 30 to 50 percent. Side effects are common, but they are mild and usually well tolerated. They include paraesthesia (tingling sensation in fingers and toes), bowel disturbances, sleepiness and increased urine volume. Acetazolamide should not be taken by individuals who are allergic to sulpha drugs. Spironolactone 25 mg 4 times a day, can be used in those allergic to sulpha medication but efficacy studies are limited.

Salmeterol inhaler: (Serevent, Oxis) 125mg inhaled 12 hourly starting the day before ascent has recently been shown to be useful in preventing HAPE. It should be used in conjunction with Acetazolamide.

Dexamethasone: is a cortisone-like medication and is superior to acetazolamide in preventing AMS; the dose is 2 to 4 mg every 6 hours, begun the day of the ascent, continued for 3 days at the higher altitude, then tapered over 5 days. Symptoms of AMS have been observed after the abrupt discontinuation of the drug. However it is mostly reserved for treating AMS

OTHER CONSIDERATIONS
Higher risk of UV sunlight injuries, hypothermia, thrombophebitis (dangerous blood clots in leg veins) and retinopathy (eye damage) occur. Insurance to cover helicopter evacuation may save you a $100,000 bill.

TREATMENT OF ACUTE MOUNTAIN SICKNESS?

Mild AMS
The rule is to remain at the same altitude until you have recovered. This often takes only 1 or 2 days. Most cases of mild AMS will improve with rest, aspirin or paracetamol in normal doses, and avoidance of alcohol. If necessary, descent of a few hundred metres is usually curative. Insomnia should not be treated with sleeping pills, since they tend to aggravate a low oxygen level during sleep.

Severe AMS
The most effective and important immediate measure in those with severe AMS is descent or evacuation to a lower altitude. Frequently a descent of 500-1000 m is sufficient.
Additional measures include oxygen, Dexamethasone (8 mg initially, then 4 mg every 6 hours for 1 to 3 days, then tapered over 5 days), nifedipine (a calcium channel blocker, 10mg every 8 hours) for high altitude pulmonary oedema and acetazolamide.
Drug treatment should never be used to avoid descent, or enable further ascent, by a person with AMS. A portable hyperbaric chamber such as the Gamow, Certec bag (a large portable airtight bag with an air pump) may be very useful in diagnosing and treating AMS. Like medication, however, it is no substitute for evacuation of a victim. The total packed weight of the bag and pump is approximately 5 - 7 Kg (pump included).

Initial information source:- Fairfield Hospital Travel information pamphlet:- 1994

Medical Examination after travel: It is advisable (if not essential) to visit your local doctor promptly if you

suffer from a chronic disease, such as cardiovascular disease, diabetes mellitus, chronic respiratory disease;

experience illness in the weeks following their return home, particularly if fever, persistent diarrhoea, vomiting, jaundice, urinary disorders, skin disease or genital infection occurs;

consider that you may have been exposed to a serious infectious disease while travelling;

have spent more than 3 months in a developing country.