The Importance of Hydration at Altitude - Dr Ross Anderson

Hydration at altitude is even more important than at sea level. Spotting early signs of dehydration is absolutely critical to a mountaineer's success. Dr Ross Anderson takes us through the signs of dehydration and what to do if you are dehydrated on the mountain.

What is dehydration? 

Water usually enters the body as liquids and a small amount in food. Dissolved in water are salt and electrolytes that also play a vital role in the smooth running of body systems. Water and salt/electrolytes can leave the body as urine, sweat and sometimes vomit or diarrhoea.

Dehydration is a serious condition where the body is short of the required amount of water to function normally. Mild dehydration is common in those who are active in the mountains and is a result of more water leaving the body than is taken on board.  On average, 1.5L to 3 litres of water is required per day in an adult at sea level. However, more water is required in situations where you come down with diarrhoea/vomiting, in warm/hot conditions, when exercising and when acclimatising to high altitudes.

The symptoms of dehydration are not always easy to recognise.

Thirst is not as reliable as you may think.  The first symptoms tend to be tiredness, weakness, a moderate to severe headache, irritability and dizziness.  These are also symptoms that we associate with other common conditions in the mountains, namely Acute Mountain Sickness and to a lesser extent, low levels of sugar in the blood. We therefore have to be mindful of the need to consider other conditions at the same time.

The key to recognising dehydration is when you pass small amounts of dark urine - hence it is important you keep an eye on the urine's colour. This is because the kidneys are trying to preserve water.

More severe dehydration can be detected through sunken eyes, a dry tongue and a weak, rapid pulse and breathing rate.

Treatment of dehydration:

The aim is to slow down body water losses and begin replacing water.  When dehydration is due to exercise at altitude, this usually requires a combination of drinking more, resting and cooling down.  Non-diet drinks and snacks containing sugar can help in cases where low blood sugar levels are also present.

If you are dehydrated due to exercise and are able to eat, then small but regular sips of plain water is all that is required to rehydrate. If little food is being eaten for whatever reason and dehydration more severe, oral rehydration solutions should be considered.

Oral rehydration solutions:

These replace vital salts and electrolytes that the body depends on to function normally. It also makes it easier for your body to retain water when drinking the solution, which can be a problem if you only drink plain water and are not eating. You can buy sachets of rehydration salts or even make it up yourself.

In severe cases of dehydration, a medical opinion is required and some cases end up being put on a drip e.g. those unable to keep any fluids down due to persistent vomiting. Hopefully after reading this article you will be better able to spot the early signs of dehydration and step in before it becomes more severe.

For more information, see Chapter 18 of Pocket First Aid and Wilderness Medicine 3rd edition by Drs Jim Duff and Ross Anderson (our past and present medical experts). You can buy a copy from TrekSafe or Cicerone Press.