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 About Body Water Water accounts for about one half to two thirds of an average person’s weight. Fat tissue has a lower percentage of water than lean tissue and women tend to have more fat, so the percentage... read more ). 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

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 Dizziness or Light-Headedness When Standing Up In some people, particularly older people, blood pressure drops excessively when they sit or stand up (a condition called orthostatic or postural hypotension). Symptoms of faintness, light-headedness... read more ). If dehydration continues, shock Shock Shock is a life-threatening condition in which blood flow to the organs is low, decreasing delivery of oxygen and thus causing organ damage and sometimes death. Blood pressure is usually low... read more 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.

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 Excessive Sweating People with excessive sweating (hyperhidrosis) sweat profusely, and some sweat almost constantly. Excessive sweating usually has no clear cause but is sometimes caused by infections, metabolic... read more , vomiting Nausea and Vomiting in Adults Nausea is an unpleasant feeling of needing to vomit. People also may feel dizziness, vague discomfort in the abdomen, and an unwillingness to eat. Vomiting is a forceful contraction of the stomach... read more , and diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more ) result in a loss of electrolytes Overview of Electrolytes More than half of a person's body weight is water. Doctors think about water in the body as being restricted to various spaces, called fluid compartments. The three main compartments are Fluid... read more (especially sodium and potassium), even more water is lost, so sodium becomes more concentrated in the blood.

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.

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 Treatment Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more 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.

People who are vomiting may not be able to hold down enough fluid to treat dehydration. More severe dehydration requires treatment by doctors with intravenous solutions containing sodium chloride (salt). The intravenous solution is given rapidly at first and then more slowly as the physical condition improves.

Treatment is also directed at the cause of dehydration. For example, when people have nausea and vomiting Nausea and Vomiting in Adults Nausea is an unpleasant feeling of needing to vomit. People also may feel dizziness, vague discomfort in the abdomen, and an unwillingness to eat. Vomiting is a forceful contraction of the stomach... read more or diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more , drugs to control or stop the vomiting or diarrhea may be used.