Acute Mountain Sickness (AMS)AMS reflects a lack of acclimatization. It is not a reflection of lack of fitness or ‘a failure’ and its presence should not be ignored as the consequences can be serious. People most at risk include those with prior episodes of AMS, fast ascent, and higher altitudes. Other factors include degree of physical exertion and factors in individual susceptibility (including being overweight). Planned activities may not be possible to complete during the first few days at altitude. Sea-level fitness is not protective for altitude illness.
Symptoms Symptoms include headache, loss of appetite, nausea/vomiting, fatigue/weakness, dizziness/lightheadedness and insomnia. Severity can be graded according to tools such as the Lake Louise self-assessment scoring system (LLS). Mild high altitude headache (HAH) is common. People with persistent headache (despite initial treatment) and one of the other symptoms at altitude should assume they have AMS. A headache does not have to be present to have AMS but is usually present.
Prevention The best way to prevent AMS is slow ascent allowing sufficient time for acclimitization. Those travelling above 3000m should not ascend over 300m/day and have a rest day for every 1000m gained. Acetazolamide is a diuretic medication that is used to prevent and treat AMS. It is the most effective drug for prevention of AMS and is particularly of use in people with a history of altitude illness on previous trips/ascents. The effect of this medication is to speed up acclimatization. It does not protect against worsening AMS with continued ascent. Acetazolamide is a sulpha-based drug although data suggests that less than 10% of those with allergy to sulpha antibitoics have an allergy to Acetazolamide. Those with previous severe allergy to sulpha drugs must not take it, those with a minor and delayed reaction (eg. rash only) could seek medical advice regarding a test dose. Side effects include taste alteration (metallic), numbness and tingling in the hands and feet and possible allergy. Used in prevention of AMS it should be commenced at least one day before ascent and used until descent has begun. Varying doses have been suggested, more commonly 125 to 250mg twice a day. Dexamethasone is a glucocorticoid (steroid) that decreases the swelling of the brain (HACE). Side effects include euphoria, difficulty sleeping and raised blood sugar levels. It is more useful in treating severe AMS and HACE. Its main role in prevention is for those who cannot take Acetazolamide or for unavoidable rapid ascents (in addition to acetazolamide). Its side-effects particularly on mood and sleep make prolonged use (more than 2-3 days) potentially problematic. Ginko biloba has had varying results in studies looking at prevention of AMS. Alcohol and sleeping tablets should be avoided.
Treatment Standard treatment of HAH includes rest (stop ascent) and pain relief (paracetamol and a nonsteroidal anti-inflammatory/NSAID). The treatment of mild AMS (LLS<4) includes rest (stop ascent) for 24hrs, pain relief and acetazolamide. Descent (300-500m) will speed recovery. More serious illness (moderate to severe AMS, LLS>4) requires oxygen (if available) and descent (300-500m) as well as pain relief, acetazolamide and dexamethasone. A hyperbaric bag can he used when descent is not possible.
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| Last Updated on Tuesday, 25 May 2010 19:54 |
