Whether you’re hiking, biking, doing some serious wilderness travel, preparing yourself for survival in the worst case scenario or just enjoying the great outdoors you should know about dehydration.
In this article you’ll learn:
- The importance of water
- What is dehydration?
- The symptoms of dehydration
- The Particular Problems Of Dehydration In The Outdoors
- Am I dehydrated?
- How to treat dehydration
The Importance Of Water
All known forms of life depend on water for their survival.
Medical textbooks generally agree that somewhere around 60 percent of adult male, and 50 percent of adult female body weight is water. This means a the amount of water in a man of average weight (70 kilograms or 154 lbs) is approximately 40 litres (85 US Pints).
Water is vital to your body both as a solvent and as an essential part of many metabolic processes within the body. It helps digest your food, transport waste, and control your body temperature. Without water, these metabolic processes could not exist and your body would begin to malfunction at a cellular level.
In short, water is essential to human life.
What Is Dehydration?
Dehydration is defined as the excessive loss of body fluid. It’s important to remember that dehydration does not only mean loss of water. Water and electrolytes (mainly sodium and potassium) are usually lost in roughly the same proportion they exist in blood plasma.
The Symptoms Of Dehydration
If you’re dehydrated, you’ll start to notice thirst and discomfort, headaches similar to having a hangover possibly along with loss of appetite and dry skin. If you’re hiking, skiing, biking or some other strenuous activity, you may experience flushing, low endurance, rapid heart rate, elevated body temperatures, and rapid onset of fatigue.
Dehydration symptoms generally become noticeable after 2% of your normal water volume has been lost.
Think about this for a second. If you weigh 70 kilos (154 lbs) your body contains around 40 litres (85 US Pints) of water when you are hydrated. A 2% loss is just under a litre – 800ml to be precise (1.7 US Pints). This means by the time you start noticing the symptoms of dehydration you’re probably already short of nearly a litre of fluids.
If dehydration continues, you may notice other symptoms including decreased urine volume, abnormally dark urine, cloudy urine, stinging during urination, sudden episodes of visual snow, unexplained tiredness, irritability, lack of tears when crying, headache, dry mouth, decreased blood pressure (hypotension) and dizziness when standing due to orthostatic hypotension.
In moderate to severe dehydration, there may be no urine output at all. This is where it starts to get serious. Symptoms include lethargy or extreme sleepiness, seizures, fainting, and sunken eyes.
The symptoms become increasingly severe with greater water loss. Heart and respiration rates increase to compensate for decreased plasma volume and blood pressure. Body temperature may rise as the body struggles to sweat.
At around 5% to 6% water loss (this is still only around 2 litres (2.1 US Pints) for our 70 kilo example) , you may become groggy or sleepy, experience headaches or nausea, and may feel tingling in your limbs (paraesthesia)
With 10% to 15% fluid loss, your muscles may become spastic, your skin may shrivel and wrinkle (decreased skin turgor)
Fluid losses greater than 15% are usually fatal.
Particular Problems Of Dehydration For The Wilderness Traveller
As you can imagine from these symptoms, anything beyond minor dehydration can cause serious problems when you are engaged in wilderness travel, using cutting tools or making navigation decisions. In a survival situation longer than a day or two, your ability to secure water will probably make the difference between life and death.
When you are removed from the reliable, easy, clean sources of water you usually have on tap (sorry!) you need to take care of what you drink and work hard to make sure you drink enough. Water, rather than being a commodity, assumes its rightful position as something that is precious – a vital preserver of your life and your body’s ability to function.
Both hypothermia and hyperthermia are very much linked with hydration. Blood plasma volume is key to your body’s ability to maintain an optimal core temperature. Think of your home heating system or your car’s cooling system. When either of these run low on fluids the entire system breaks down.
If you lead or travel with groups in the outdoors, dehydration, along with hypothermia and hyperthermia, should be closely monitored in the group as one individual’s problem can quickly turn into a serious situation for the whole group.
If water is being lost through vomiting or diarrhoea, an electrolyte imbalance can develop very quickly into a medical emergency. In remote wilderness areas this is a dangerous situation, especially for the lone traveller. To avoid finding yourself in a survival situation you should make it your business to know the ins and outs of purifying drinking water and pay close attention to hygiene and sanitation.
Similarly, fever and burns (including sunburn) increase body temperature requiring more fluid for the body to function properly.
Am I Dehydrated?
Thirst isn’t a reliable indicator and often lags behind your actual need for hydration. There are a couple of easy ways to keep an eye on your hydration:
The old favourite is to monitor the frequency and character of your urination. If your bladder is full at least every 3–5 hours and your urine is a light straw colour, it’s unlikely that dehydration is occurring. If your urine is deeply coloured and/or you urinate infrequently or not at all, your fluid intake probably isn’t enough to maintain proper hydration.
Another quick indicator is saliva. If you can draw plenty of saliva into your mouth – as if you’re about to spit – it’s a rough and ready indicator of adequate hydration. This is an easy way for the an outdoor group leader to monitor their group. Group members are often less than keen for you to closely inspect their urination habits! (Of course for the outdoor leader working in snow the urination of others can be monitored easily!).
How To Treat Dehydration
The most effective treatment for minor dehydration is drinking water and stopping excessive fluid loss. Small, frequent sips provide your body with the best chance to absorb fluids. Remember that plain water restores only the volume of the blood plasma and doesn’t restore electrolyte balance.
For minor dehydration this shouldn’t be a problem but if you’ve been sweating heavily and rehydrating solutions are available it might be worth taking a sachet. If you don’t have rehydrating solution with you dissolve a small amount of salt in water or try flat fizzy drinks (soda) – if you happen to have such things with you.
More severe cases require the replenishment of necessary water and electrolytes through oral rehydration therapy or fluid replacement by intravenous therapy. As oral rehydration is less painful, less invasive, less expensive, and easier to provide, it is the treatment of choice for mild dehydration. Solutions used for intravenous rehydration must be isotonic or hypotonic. Pure water injected into the veins will cause the breakdown of red blood cells. At this stage you’re needing professional medical care and evacuation.
Sources for further in depth study
Textbook of medical physiology, Guyton & Hall 2006