Dehydration

Dehydration is not having enough water in the body.

Sometimes people dismiss dehydration as a minor nuisance. However, without treatment, dehydration can have serious effects, including confusion (delirium), dizziness, falls, and death.

When a person is dehydrated, blood pressure falls, the body's organs do not receive enough blood and nutrients, and the body cannot cool itself adequately. Also, the levels of many electrolytes tend to become abnormal. The body tries to keep blood pressure from falling by moving water from cells and the spaces around the cells into the blood vessels. Then, the tissues dry out. The kidneys try to conserve water by concentrating urine more or by not making any urine.

Dehydration can occur at any age. But older people are prone to dehydration because of changes that occur as the body ages—for example, older people sense thirst less quickly and intensely, and the kidneys function less well. Other conditions that make dehydration more likely include the following:

• Hot weather, because sweating is increased
• Fever, because sweating is increased and breathing becomes more rapid (causing more water to be lost in the air that is breathed out)
• Diarrhea, because water is lost in the stool
• Vomiting, because water is lost in the vomit
• Diabetes that is poorly controlled, because the body produces more urine
• Kidney disorders, because the kidneys are less able to concentrate urine as needed
• Problems with walking, because getting water is difficult
• Dementia, because the sense of thirst is reduced and the ability to get water when needed is impaired
• Use of diuretics, because these drugs increase the amount of water (and salt) excreted by the kidneys

Symptoms and Diagnosis

When dehydration is mild, the skin and the membranes of the nose and eyes become dry. A dehydrated person may feel confused and sluggish. After standing up, the person may feel light-headed and may faint. As dehydration becomes more severe, the body makes less urine, and the urine becomes dark. Severe dehydration can lead to a fall in blood pressure that can be life threatening.

Blood and urine tests help doctors diagnose dehydration and determine how severe it is. Doctors measure levels of certain electrolytes and other substances that indicate how well the kidneys are functioning.

Treatment

Treatment involves replacing lost fluids. How rapidly they are replaced depends on how severe dehydration is. People who have mild dehydration are usually given about 2 to 3 liters of water to drink over a period of a few hours. People who have moderate dehydration are usually given a fluid that contains some salt (sodium) and other electrolytes. Dilute broths and rehydration formulas (available in pharmacies without a prescription) are a good choice.

Some people must be given fluids through a tube inserted in a vein (intravenously). Such people include those who are severely dehydrated, those who cannot swallow, and those who are in a coma. If electrolytes must also be replaced, they are given intravenously with the fluids.