Getting High: An Update In Altitude Medicine

With Australians now frequently travelling to high altitude destinations around the world, the field of altitude and expedition medicine is growing. I attended the 5^th Update in Altitude and Expedition Medicine conducted by Queensland-based Medicine on the Edge. The conference was held on the slopes of Mount Kilimanjaro, Tanzania; and concluded with a climb to the summit, at 5,895 metres, the highest point in Africa.

Following a midnight breakfast, we set off for the summit under a moonlit sky. (Author’s diary, Barafu 4,600m).

For some, mountain climbing epitomises challenge and achievement. For others, it is immersion in a timeless world of untamed beauty. In practice, Kilimanjaro is a high altitude walk requiring some clambering and crawling. It is physically accessible to many with suitable preparation. The effects of high altitude however can test the fittest of lowlanders.

Considerations for Expedition at Altitude

Mountain climbing is not necessarily good for you. There are specific high altitude syndromes which if not addressed can present serious risk to the mountaineer. In addition, frostbite, high UV exposure, loss of appetite, reduced carbohydrate absorption, dehydration and hyponatraemia are all associated with high altitude. Lightning strike, avalanche and other physical hazards outside human control may also be encountered.

Medical assistance and retrieval services are not always available. Even if in range, rescue helicopters typically have an operational ceiling of 4,000 to 5,500 metres which is well below many peaks. Good planning, preparation and knowledge of acute altitude syndromes are therefore essential to ensure safety on the slopes.

Any intending climber with chronic conditions is well advised to consult their current specialists about the safety of their proposed itinerary. A history of cardiac, pulmonary or psychiatric illness presents particular risks at altitude. In all cases, medication use needs to be stabilised and the effects of freezing considered for sensitive medicines such as insulin.

For women, travel above 2,500 metres in the first trimester of pregnancy risks miscarriage and is strongly advised against. Furthermore, most of the medications used for altitude illness are contraindicated in pregnancy. Female climbers are recommended to carry a pregnancy test kit so that ectopic pregnancy in particular can be ruled out in the event of abdominal pain. This may avoid an emergency evacuation.

Altitude illness

With increasing altitude, atmospheric pressure declines so the amount of oxygen available to breathe is less. Acute altitude sickness is caused by hypobaric hypoxia in which inadequate oxygen is transferred into the blood. Reduced oxygenation directly impairs metabolism and affects many organ systems. It also triggers compensatory changes in vascular tone with consequent cerebral or pulmonary fluid shift that leads to symptoms.

The rate of ascent, maximum altitude attained, sleeping elevation, and strenuous exercise at altitude are known risk factors for the development of altitude sickness. Individual susceptibility also varies and is not readily predictable. Altitude related syndromes are commonly distinguished according to definitions adopted at the Lake Louise Hypoxia and Mountain Medicine Symposium held in Canada 1991.

High Altitude Headache (HAH) is the most commonly experienced high altitude illness, affecting 80% of people who ascend to high altitude. A throbbing, bi-temporal or occipital, band-like headache develops within 24 hours of ascent above 2,500 metres. It is often worse at night and early morning, on exertion, and lying down. HAH resolves with oxygen, paracetamol, ibuprofen and hydration. It is recommended that the climber descend to lower altitude if there is no improvement.

Sitting…I have a mild headache but no other issues.
(Author’s diary, Moir Camp 4,200m)

Acute Mountain Sickness (AMS) occurs following gain in altitude. It is characterised by the presence of headache and at least one of the following symptoms: anorexia, nausea or vomiting, fatigue or weakness, dizziness or light-headedness, disturbed sleeping which may be related to periodic breathing. Apathy, photophobia, irritability and reduced urinary output may also occur. Even with acclimatisation, AMS affects 77% of climbers reaching the summit of Mount Kilimanjaro.

A long cold night…not restful and I frequently need to move.
(Author’s diary, Lava Tower 4,610m)

High Altitude Cerebral Oedema (HACE) can be considered ‘end stage’ or severe AMS. In the setting of a recent gain in altitude, HACE is defined as the presence of either a change in mental status and/or ataxia in a person with AMS; or mental status changes with ataxia in a person without AMS.

High Altitude Pulmonary Oedema (HAPE) is defined as the presence of at least two of the following symptoms: dyspnoea at rest, cough, weakness or decreased exercise performance, chest tightness or congestion, plus at least two of the following signs: pulmonary crackles or wheezing, central cyanosis, tachypnoea, or tachycardia.

Breathing is the greatest challenge. I have difficulty with any additional exertion. (Author’s diary, Climbing to Stella Point 5,756m)

Prevention

The best preventative strategy for altitude illness is gradual ascent to allow acclimatisation. Ideally individuals should take two or more days to ascend to an initial 3,000 metres, with subsequent increases in sleeping elevation of no more than 500 metres each day.

I feel better today although my oxygen saturation is down to 79% at rest.
(Author’s diary, Lava Tower 4,610m)

Very rapid ascent above 3,000 metres, as is frequently undertaken when climbing Mount Kilimanjaro, presents a high risk of developing AMS. In such situations, preventative acetazolamide should be considered.

Acetazolamide is a carbonic anhydrase inhibitor. By promoting acidosis, it stimulates respiration and so improves oxygenation. The resultant regular breathing may also alleviate sleep problems at altitude.

All but one climber of our group took acetazolamide, 125mg orally twice a day, from the day before ascent until beginning our descent. The fellow who abstained, although very fit, developed symptoms of AMS. Most of us experienced known side effects such as tingling fingers, toes or lips; metallic taste and polyuria. These effects were tolerable and nocturnal polyuria whilst inconvenient emboldened us to brave the cold and gaze at the extraordinary high altitude night sky.

Dexamethasone is recommended as a second line agent for AMS prophylaxis. Nifedipine, tadalafil, sildenafil or inhaled salmeterol may also be protective in individuals with a history of HAPE, but should only be used on specialist advice.

Treatment

Anyone with altitude illness of any severity should stop, rest, and rehydrate. Simple analgesics and antiemetics may help.

In the case of HACE or HAPE descent is the highest priority. Supplemental oxygen and a portable hyperbaric chamber may be of benefit if descent is delayed by weather, or for logistical reasons. Symptoms typically start to improve following descent of 300 to 1,000 metres, but may persist for a number of days in severe cases. Further ascent is not advisable without medical clearance.

There is good evidence for the use of drug therapies in conjunction with descent for severe altitude illness. For adults with severe AMS or HACE, use dexamethasone 8mg orally, IV or IM for the first dose, then 4mg six-hourly.

For adults with HACE who can take oral medications, consider adding acetazolamide 250mg orally. In adults with HAPE, nifedipine controlled-release 20mg orally, eight-hourly may be used. Dexamethasone should be added to nifedipine for patients with concurrent HAPE and HACE.

We encountered a young Norwegian being carried down by his brother and porter. Unable to stand unaided or respond to others, he was fortunate to stumble into our conference group. After a mountainside consultation and dexamethasone, he was able to proceed down to a safer altitude.
(Author’s diary, Descent to Millennium Camp, 3,800m)

High Attitude

Kilimanjaro certainly proved the most challenging workshop I have attended. Although our planning, research and physical preparation was rewarded, the experience of sustained exertion at high altitude pushed boundaries well beyond what I had envisaged. All of the party I had trained with made it to the summit. It made our usual daily challenges seem small. Some described it as the hardest thing they had ever done.

Mountaineering isn’t for everyone. However, if a recreational climb it is on your ‘bucket list’, then go for it! Climb with an experienced team and allow adequate time for acclimatisation. Take advice on an appropriate medical kit. Check the current availability of medical and evacuation services. Obtain appropriate medical insurance before you go. And have the experience of a lifetime!