Dehydration occurs because more fluid is lost from the body than is taken in. Water is essential for life. Transporting nutrients throughout the body, removing wastes, regulating body temperature, lubrication of joints and membranes, and chemical reactions that occur during cellular metabolism all require water.
The amount of water a person needs to prevent dehydration varies widely depending on the individual’s age, weight, level of physical activity, and the environmental temperature. The individual’s health and the medications they take may also affect the amount of water a person needs. Most dehydration results from an acute, or sudden, loss of fluids. However, slow-developing chronic dehydration can occur, most often in the frail elderly and infants and young children who must rely on others to supply them with liquids.
Healthy people lose water from urination, elimination of solid wastes, sweating, and breathing out water vapor. This water must be replaced through diet. Water makes up about 75% of the body weight of infants, 65% of the weight of children and 60% of the weight of an adult. In 2004, the United States Institute of Medicine (IOM) recommended that relatively inactive adult men take in about 3.7 L (about 15 cups) of fluids daily and that women take in about of 2.7 liters (about 10 cups) to replace lost water. These recommendations are for total fluid intake from both beverages and food. Highly active adults and those living in very warm climates need more fluids.
About 80% of the water the average person needs is replaced by drinking liquids. The other 20% is found in food. Below are listed some foods and the percentage of water that they contain.
* iceberg lettuce 96%
* squash, cooked. 90%
* cantaloupe, raw, 90%
* 2% milk 89%
* apple, raw 86%
* cottage cheese 76%
* potato, baked 75%
* macaroni, cooked 66%
* turkey, roasted 62%
* steak, cooked 50%
* cheese, cheddar 37%
* bread, white 36%
* peanuts, dry roasted 2%
Dehydration involves more than just water deficiency. Electrolytesare ions that form when salts dissolve in water or body fluids. In order for cells to function correctly, the various electrolytes, such as sodium(Na+ ) and potassium (K+), must remain within a very narrow range of concentrations. Often electrolytes are lost along with water. For example sodium is lost in sweat. To prevent the effects of dehydration, both water and electrolytes must be replaced in the correct proportions.
The very young and the very old are most likely to become dehydrated. Young children are at greater risk because they are more likely to get diseases that cause vomiting, diarrhea, and fever. Worldwide, dehydration is the leading cause of death in children. In the United States, 400–500 children under the age of 5 die every year of dehydration. The elderly are at risk because they are less likely to drink when they become dehydrated. The thirst mechanism often becomes less sensitive as people age. Also, their kidneys lose the ability to make highly concentrated urine. Older individuals who are confined to wheelchairs or bed and cannot get water for themselves (e.g. nursing home and hospital patients) are at risk of developing chronic dehydration.
Causes and symptoms
Diarrhea, often accompanied by vomiting, is the leading cause of dehydration. Both water and electrolytes are lost in large quantities. Diarrhea is often caused by bacteria, viruses, or parasite. Fever that often accompanies disease accelerates the amount of water that is lost through the skin. The smaller the child, the greater the risk of dehydration. Worldwide, acute diarrhea accounts for the death of about 4 million children each year. In the United States, about 220,000 children are hospitalized for dehydration caused by diarrhea annually.
Heavy sweating also causes dehydration and loss of electrolytes. Athletes, especially endurance athletes and individuals with active outdoor professions such such as roofers and road crew workers are at high risk of becoming dehydrated. Children who play sports can also be vulnerable to dehydration.
Dehydration can be mild, moderate or severe. Mild dehydration occurs when fluid losses equal 3– 5%. At this point, the thirst sensation is felt, and is often accompanied by dry mouth and thick saliva.
Moderate dehydration occurs when fluid losses equal 6–9% of their body weight. This can occur rapidly in young children who are vomiting and/or have diarrhea. In an infant, a loss of as little as 2–3 cups of liquids can result in moderate dehydration. Signs of moderate dehydration include intense thirst, severely reduced urine production, sunken eyes, headache, dizziness, irritability, and decreased activity.
Severe dehydration occurs when fluid losses are 10% or more of their body weight. Severe dehydration is a medical emergency for individuals of any age. A loss of fluids equaling 20% of a person’s body weight is fatal. Signs of severe dehydration include all those of moderate dehydration as well as lack of sweating, little or no urine production, dry skin that has little elasticity, low blood pressure, rapid heartbeat, fever, delirium, or coma.
Dehydration is diagnosed by physical symptoms. A healthcare professional or observant adult can usually tell by looking at someone that they are moderately or severely dehydrated. Blood tests and a urinalysis may be done to check for electrolyte imbalances and to determine if the kidneys are damaged. However, visual signs are enough to begin treatment.
The goal of treatment is to restore fluid and electrolyte balance. For individuals with mild dehydration, this can be done in infants and children by giving them oral rehydration solutions such as Pedialyte, Infa-lyte, Naturalyte, Oralyte, or Rehydralyte. These are available in supermarkets and pharmacies without a prescription. These solutions have the proper balance of salts and sugars to restore the electrolyte balance. Water, apple juice, chicken broth, sodas, and similar fluids are effective in treating mild dehydration. Oral rehydration fluids can be given young children in small sips as soon as vomiting and diarrhea start. They may continue to vomit and have diarrhea, but some of the fluid will be absorbed. Breastfed infants should continue to nurse on demand. Babies who are formula fed should continue to get their regular formula unless directed otherwise by a pediatrician.
Older children who are dehydrated can be given oral rehydration solutions or sports drinks such as Gatorade for moderate and severe dehydration, otherwise general fluids are fine. Athletes who are dehydrated should be given sports drinks. According to the American College of Sports Medicine, sports drinks are effective in supplying energy for muscles, maintaining blood sugar levels, preventing dehydration, and replacing electrolytes lost in sweat. Adults who are mildly or moderately dehydrated usually improve by drinking water and avoiding coffee, tea, and soft drinks that do not contain caffeine.
Individuals of all ages who are seriously dehydrated need to be treated by a medical professional. In the case of severe dehydration, the individual may be hospitalized and fluids given intravenously (IV; directly into the vein).
Dehydration is usually an acute condition, and once fluid balance is restored, there are no additional nutritional concerns. In the mobility-impaired elderly, the main concern is making sure that they have adequate access to fluids.
Most people recover from dehydration with few complications so long as rehydration fluids are available and treatment begins before the condition becomes severe. However, severe dehydration can be fatal.
The best way to prevent dehydration is to be alert to situations in which it could occur, such as exercising in hot weather or vomiting and diarrhea in infants and young children. Athletes and people who work in hot conditions should drink regularly, whether or not they feel thirsty. Rehydration of young children should begin at the first sign of fluid loss. A healthcare provider should be consulted before the situation becomes serious. Caregivers of the mobility impaired elderly and infants and young children who cannot get water for themselves should be offered fluids on a regular basis.