Dehydration is defined as sweat, urine or respiratory water loss. It happens when the body reduces its intake of water and this loss of water also removes important blood salts like potassium and sodium.
When endorphins (chemicals that the body uses to fight stress) take over, the thirst mechanism is disregarded. So being thirsty is not a good indicator for how dehydrated one might be. Vital organs like the kidneys, brain, and heart can’t function without a certain minimum of water and salt. To understand how important water is to the human body consider the following facts:
- The body is between 45%-75% water.
- The average 160 lb. male contains about 45 litres of water, or 6% of his body weight.
- You can lose 2% of your body weight before thirst is initiated, which may get worse as the severity of dehydration increases.
- With 4%-6% body water loss, you are impatient and you have symptoms of headache.
- With 10% loss, you have dizziness and cyanosis. You also become light-headed and have fainting episodes.
- With 12% loss, you have difficulty swallowing and you require assistance in re-hydration.
- 15%-25% water loss can cause death.
- Sweat rates can be as high as 1-1/2 liters per hour, or roughly 15 liters a day.
At high altitudes, perspiration evaporates from the skin almost immediately and water requirements can be very similar to those in the desert.
The only method the human body has to stay cool when the temperature is high is by means of sweating. Sweating takes water away from the body. Sweat glands in the deep layer of the skin, the dermis, make sweat by filtering fluid and salts out of the blood, and secreting this fluid up through small tubes in the skin, the sweat ducts, that empty out into small pores at the top layer of the skin to cool it’s outer surface.
Dehydration can happen in any survival situation, whether you are in a rain forest, desert or on the ocean. When dealing with dehydration, you must first address the cause which could one of or a combination of the following:
- High Temperature
- Reduced intake of fluids
The dangers of dehydration are two fold. First, dehydration decreases a person's ability to withstand the effects of high temperature. As dehydration progresses, there is increased heat discomfort and decreased ability to perform normal physical activities.
Equally important is the effect of dehydration on a person's mental capacity. Even at levels of dehydration in which there is little physical impairment, a person's ability to think clearly and make rational decisions can be affected. Some of the mental effects of dehydration include irritability, depression, confusion and disorientation. This can cause even the best prepared person to make mistakes, which can be fatal in a survival situation.
It is important to recognise the signs of dehydration, particularly in its early stages:
The signs of mild dehydration:
- Dry Lips
- Slightly dry mouth and membranes
The signs of moderate dehydration:
- Very dry mouth membranes
- Sunken eyes
- Skin doesn’t bounce back quickly when lightly pinched and released
The signs of severe dehydration:
- All signs of moderate dehydration
- Rapid, weak pulse (more than 100 at rest)
- Cold hands and feet
- Rapid breathing
- Blue lips
- Confusion, lethargy, difficult to arouse
If urine becomes darkened or scant then fluid requirements are not being met. The only way to keep from becoming dehydrated is to drink a sufficient amount of water. The water should be cool, good tasting and convenient, so the person will be inclined to drink often. Never rely on thirst to determine how much to drink. In hot weather thirst does not keep pace with the body's need for water, so a person should drink a lot more than they feel like drinking. Even if they find themselves in a survival situation they must not try to conserve water. It is the water in the body that prevents dehydration, not the water in the bottle.
It is difficult to predict how much water is needed to prevent dehydration. Many factors affect water requirement, among these the most important are temperature, physical activity, body size, and clothing. In actual situations water consumption of more than three gallons per day for one person has often been observed. Some very rough estimates for water replacements:
- In the cold: Approximately 2 quarts per day
- In severe cold with heavy exercise: Up to 2 gallons
- Altitudes above 10,000 feet: more than 2 gallons
As a general rule anyone out of doors should consume at least 3 - 4 quarts of fluid per day. If you're engaging in even moderate activity this should be increased to 4 - 6 quarts.
There is advice that a person should saturate their system to ensure that they are properly hydrated. To saturate the system, drink as much as can be held and urinate. Repeat the process several times and the body will have as much water as it can hold. You want to be able to urinate pale yellow. Drink by your watch in hot environments. Forced drinking in the absence of thirst saves lives in the heat.
Other advice includes:
- When the mouth feels dry, keep a small pebble in it to suck on.
- Breathe through the nose to keep moisture from escaping through your breath. Do not spit.
- Try not to work hard enough to perspire.
In order to carry water successfully a good bottle is required. These need to be hard wearing and have the ability to keep water cool and be easily cleanable. Bacteria can thrive in a water bottle, particularly in warm conditions. Bottles should be washed regularly. Also, water bottles should not be shared because of the possibility of cross infection. It is not unheard of for whole groups to fall sick from sharing water bottles. If possible all water that has not come from a treated source such as a tap or commercial bottle should be boiled or treated chemically.
To sum up, the most important thing to remember about dehydration is to prevent it before it happens. Feeling thirsty is an indicator but it is not the start of dehydration. With only a loss of five percent of your body weight you will be in trouble. When you feel thirsty it is already too late, drink BEFORE you feel thirsty. In a survival situation, it cannot be stressed enough: If you cannot get to a clean water supply, GO AHEAD AND DRINK THE WATER. It is always best to rehydrate the body, from whatever source. Your survival might depend on it. When you are then found and get back to a location where you can be treated, the healthcare professionals can treat your symptoms at that point in time.