Dehydration

Dehydration facts

The body needs water to function.

Dehydration occurs when water intake is less than water loss.

Symptoms range from mild to life-threatening.

The young and the elderly are especially susceptible to dehydration.

What is dehydration?

Water is a critical element of the body, and keeping the body adequately hydrated is a must to allow the body to function. Up to 75% of the body's weight is made up of water. Most of the water is found within the cells of the body (intracellular space). The rest is found in the 

extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water in the body. We lose water routinely when we:

breathe and humidified air leaves the body (this can be seen on a cold day when you can see your breath in the air, which is just water that has been exhaled);

sweat to cool the body; and

eliminate waste by urinating or having a bowel movement.

The formula for daily fluid requirements depends upon an individual's weight. Normally, fluid and weight are calculated using the metric system; however, below is the approximation in imperial (American) units.

Body weight Daily fluid requirements (approximate)

10 pounds 15 ounces

20 pounds 30 ounces

30 pounds 40 ounces

40 pounds 45 ounces

50 pounds 50 ounces

75 pounds 55 ounces

100 pounds 50 ounces

150 pounds 65 ounces

200 pounds 70 ounces

If you would like to calculate your body weight and daily fluid requirements using the metric system, please use this formula.

For the first 10kg (kilogram) of body weight the daily fluid intake required is 100cc (or mL) per kg.

For the next 10kg of body weight, the fluid required is an additional 50 cc/kg.

For every additional kg of body weight, an additional 10cc/kg is required

This is the basic body requirement. More fluid would be needed to replace excess sweating from exercise or fever, fluid loss from vomiting, and diarrhea or increased urine production.

What causes dehydration?

Dehydration occurs because there is too much water lost, not enough water taken in, or most commonly, a combination of the two.

• Diarrhea : Diarrhea is the most common reason for a person to lose excess amounts of water. A significant amount of water can be lost with each bowel movement. Worldwide, more than four million children die each year because of dehydration from diarrhea.
• Vomiting : Vomiting can also be a cause of fluid loss. Not only can an individual lose fluid in the vomitus, but it may be difficult to replace water by drinking because of that same nausea and vomiting.

• Sweat : The body can lose significant amounts of water in the form of sweat when it tries to cool itself. Whether the body temperature is increased because of working or exercising in a hot environment or because a fever is present due to an infection; the body uses water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk may generate up to 16 ounces of sweat (a pound of water) an hour to allow body cooling, and that water needs to be replaced by the thirst mechanism signaling the person to drink fluids.
• Diabetes: In people with diabetes, elevated blood sugarlevels cause sugar to spill into the urine and water then follows, which may cause significant dehydration. For this reason, frequent urination and excessive thirst are among the early symptoms of diabetes.
• Burns : The skin acts as a protective barrier for the body and is also responsible for regulating fluid loss. Burn victims become dehydrated because the damaged skin cannot prevent fluid from seeping out of the body. Other inflammatory diseases of the skin such as toxic epidermal necrolysis, also may be associated with significant fluid loss.
• Inability to drink fluids: The inability to drink adequately is the other potential cause of dehydration. Whether it is the lack of availability of water, intense nausea with or without vomiting, or the lack of strength to drink. This coupled with routine or extraordinary water losses can compound the degree of dehydration.