Dehydration is a deficiency of water in the body.
Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration.
People feel thirsty, and as dehydration worsens, they may sweat less and excrete less urine.
If dehydration is severe, people may be confused or feel light-headed.
Treatment is restoring lost water and mineral salts (such as sodium and potassium) that are dissolved in the blood (electrolytes), usually by drinking but sometimes with intravenous fluids.
(See also About Body Water.)
Dehydration occurs when the body loses more water than it takes in. Vomiting, diarrhea, the use of drugs that increase urine excretion (diuretics), profuse sweating (for example, during heat waves, particularly with prolonged exertion), and decreased water intake can lead to dehydration.
Dehydration is particularly common among older people because their thirst center may not function as well as that in younger people. Therefore, some older people may not recognize that they are becoming dehydrated. Certain disorders such as diabetes mellitus, diabetes insipidus, and Addison disease can increase the excretion of urine and thereby lead to dehydration.
Dehydration in infants and children is also common because the amount of fluid lost during diarrhea or vomiting may represent a larger proportion of their body fluids than in older children and adults.
Symptoms of Dehydration
At first, dehydration stimulates the thirst center of the brain, causing thirst, a powerful motivator for people to drink more fluids. If water intake does not keep up with water loss, dehydration becomes more severe. Sweating decreases, and less urine is excreted. Water moves from inside the cells to the bloodstream to maintain the needed amount of blood (blood volume) and blood pressure (see About Body Water). If dehydration continues, tissues of the body begin to dry out, and cells begin to shrivel and malfunction.
Symptoms of mild to moderate dehydration include
Thirst
Reduced sweating
Reduced skin elasticity
Reduced urine production
Dry mouth
In severe dehydration, the sensation of thirst may actually decrease and blood pressure can fall, causing light-headedness or fainting, particularly upon standing (a condition called orthostatic hypotension). If dehydration continues, shock and severe damage to internal organs, such as the kidneys, liver, and brain, occur. Brain cells are particularly susceptible to more severe levels of dehydration. Consequently, confusion is one of the best indicators that dehydration has become severe. Very severe dehydration can lead to coma and death.
Diagnosis of Dehydration
A doctor's evaluation
Sometimes blood tests
Dehydration can often be diagnosed from symptoms and the results of a doctor's examination. But sometimes doctors do blood tests for people who appear seriously ill or who take certain drugs or have certain disorders. For people who require more monitoring or testing in an emergency department or intensive care unit, doctors sometimes use ultrasound or special catheters to measure the severity of dehydration.
Dehydration normally causes the sodium level in the blood to increase. The reason is that although the common causes of dehydration (such as profuse sweating, vomiting, and diarrhea) result in a loss of electrolytes (especially sodium and potassium), even more water is lost, so sodium becomes more concentrated in the blood.
Prevention of Dehydration
Prevention of dehydration is better than cure. Adults should drink at least 6 glasses of fluids daily (including fluid from eating foods high in water content, such as fruits and vegetables). Fluid intake should be increased on hot days, when working or exercising in hot weather, during or after prolonged exercise, and, if possible, when people have vomiting and/or diarrhea.
Exercise, a high body temperature, and hot weather increase the body’s need for water. Flavored sports drinks have been formulated to replace electrolytes lost during vigorous exercise. These drinks can be used to prevent dehydration. People should drink fluids with electrolytes before and during vigorous exercise as well as afterward. Before exercising, people with heart or kidney disorders should consult their doctors about how to safely replace fluids.
People should make sure that older family members have access to plenty of water when they are alone in a hot building or place.
Treatment of Dehydration
Replacing fluids and electrolytes
For treating mild dehydration, drinking plenty of water may be all that is needed. With moderate and severe dehydration, lost electrolytes (especially sodium and potassium) must also be replaced.
Oral rehydration solutions that contain appropriate amounts of electrolytes are available without a prescription. These solutions work well to treat dehydration, especially that caused by vomiting or diarrhea in children. Sports drinks do not necessarily contain enough electrolytes to be an adequate substitute for these solutions.
Treatment is also directed at the cause of dehydration. For example, when people have nausea and vomiting or diarrhea, drugs to control or stop the vomiting or diarrhea may be used.
