Caudwell Xtreme Everest - Exploring Human Physiology At Extreme Altitude
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NEWS: 7th May 2007
 
Translating the lessons learnt from hypoxia in the mountains

"We need help urgently. We have a man in his forties who cannot move his right side"

The Caudwell Xtreme Team received this message whilst at Cho Oyu Base Camp in September 2006. Jon Morgan, who is both a mountain guide and anaesthetist, and I set off across the moraines from Advance Base Camp (5,600m) to the casualty at 5,900m. When we got there, we found a man in his mid forties unable to speak, swallow or move his right side. The possible diagnoses were that he had either had a stroke or he had high altitude cerebral oedema (HACE). We gave him steroids, oxygen and aspirin, and with a team of sherpas, we evacuated him back to ABC.

In the meantime the Caudwell Xtreme Team had set up a mini High Dependency Unit or Stroke Unit. Basic supportive treatment was started, a drip was started, and the oxygen continued. We performed a portable scan (TCD) examination (SonoSite Micromax) of the blood supply to the patient?s brain. There was reduced blood supply to the left side of the brain highly suggestive of a stroke. Over the next couple of days sherpas evacuated the patient over the moraines, and then we used a jeep to take him from the roadhead to the Tibetan-Nepalese border and finally helicopter to Kathmandu. From there he was transferred back to North America, and has gone on to make a reasonable recovery.

The brain is the most sensitive organ in the body to the lack of oxygen. Blockage of the main arteries to the brain either during surgery (or by strangulation!) will result in unconsciousness within three to four minutes and cell death or a stroke will occur shortly after that. Stroke is a major cause of both disability and death, and is the third commonest cause of death in the Western world and there are estimated 130,000 strokes each year in England and Wales.

One of the questions we are trying to answer on the Caudwell Xtreme Everest Expedition is how the brain is able to cope for long periods of time with oxygen levels that are somewhere between one half and one third normal levels. The follow on then has to be to see whether there are lessons we can learn from the apparent tolerance of the brain to lack of oxygen we see at altitude. Then can we use this knowledge to improve the outcomes in patients who suffer from the potentially devastating condition of stroke?

The modern treatment for a thrombotic (clot-based) stroke is to use clot busting drugs (thrombolytic agents) to clear the blood flow to the brain. These clot busting drugs need to be started within 3 hours of the start of symptoms of the stroke and a brain scan is needed to be certain the drug treatment is suitable. Recent evidence suggests that the TCD scanning technique that we used on the patient in Cho Oyu and are using on Everest may be useful in predicting which patients with strokes will benefit from the clot busting treatment. Currently although we have shown the technique will work in the mountains up to 6,400m, there are very few hospitals in the UK offering the technique. Convincing doctors that the TCD technique is practical in hospitals is an important step in reducing the adverse outcomes from strokes.


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