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Dehydration

Dehydration

Definition

Dehydration is the loss of water and salts that are essential for normal body function.

Description

Dehydration occurs when the body loses more fluid than it takes in. Dehydration can upset the delicate fluid-salt balance needed to maintain healthy cells and tissues. The human body is generally over 60 percent water. The body works to maintain water balance through mechanisms such as the thirst sensation. When the body requires more water, the brain stimulates nerve centers to encourage a person to drink in order to replenish the water stores. Water intake can vary widely on a daily basis, influenced by such factors as access to water, thirst, habit, and cultural factors.

The kidneys are responsible for maintaining water balance through the elimination of waste products and excess water. Water is primarily absorbed through the gastrointestinal tract and excreted by the kidneys as urine. The variation in water volume ingested is dependent on the ability of kidneys to dilute and concentrate the urine as needed.

Children need more water than adults because they expend more energy, and most children who drink when they are thirsty get as much water as their systems require. Dehydration in children usually results from losing large amounts of fluid and not drinking enough water to replace the loss. This condition generally occurs in children who have a stomach flu characterized by vomiting and diarrhea or who cannot or will not take enough fluids to compensate for excessive losses associated with fever and sweating of acute illness. Dehydration can result from illness; a hot, dry climate; prolonged exposure to sun or high temperatures; not drinking enough water; and overuse of diuretics or other medications that increase urination.

Types of dehydration

Dehydration is classified as mild, moderate, or severe based on how much of the body fluid is lost, estimated by loss in bodyweight. Mild dehydration is the loss of no more than 5 to 6 percent loss of body weight. Loss of 7 to 10 percent is considered moderate dehydration. Severe dehydration (loss of over 10 percent of body weight) is a life-threatening condition that requires immediate medical care.

Complications of dehydration

When the body's fluid supply is severely depleted, hypovolemic shock is likely to occur. This condition, which is also called physical collapse, is characterized by pale, cool, clammy skin; rapid heartbeat; and shallow breathing.

Blood pressure sometimes drops so low it cannot be measured, and skin at the knees and elbows may become blotchy. Anxiety , restlessness, and thirst increase. After a child's temperature reaches 107°F (41.7°C) damage to the brain and other vital organs occurs quickly.

Demographics

Dehydration is a major cause of infant illness and death throughout the world. Dehydration is often a result of gastrointestinal disease and diarrhea in children. Among children in the United States, short-term diarrhea results in approximately 200,000 hospitalizations and 300 deaths per year. In developing countries, dehydration from illness is a common cause of death in children under five years of age, accounting for about 2 million deaths per year.

Causes and symptoms

Dehydration is a deficit of body water that results when the output of water exceeds intake. Dehydration stimulates a child's thirst mechanism. Causes of dehydration may include the following:

  • decreased water or fluid intake
  • diarrhea
  • vomiting
  • excessive heat
  • excessive sweating
  • fever
  • excessive urination (polyuria)
  • diuretics or other medication that increase fluid loss
  • caffeine or alcohol consumption

Sweating and the output of urine both decrease during dehydration. If water intake continues to fall short of water loss, dehydration worsens and a child may become critically ill.

Reduced fluid intake may be a result of the following:

  • appetite loss associated with acute illness
  • nausea
  • bacterial or viral infection or inflammation of the pharynx (pharyngitis)
  • inflammation of the mouth caused by illness, infection, irritation, canker sores , or vitamin deficiency

Other conditions that can lead to dehydration include the following:

  • disease of the adrenal glands, which regulate the body's water and salt balance and the function of many organ systems
  • diabetes mellitus
  • eating disorders
  • kidney disease
  • chronic lung disease

With mild dehydration, increased thirst and restlessness are usually the only apparent symptoms. In moderately dehydrated children, eyes are somewhat sunken, and the mouth and tongue are dry. Thirst is increased: an older child asks for water, and a younger child drinks eagerly when offered a cup or spoon of water. The skin is less elastic than it should be and is slow to return to its normal position after being pinched. The radial pulse (wrist area) is detectable, but rapid. The soft spot on a baby's head (fontanelle) is somewhat sunken. Two of the following symptoms usually indicate some degree of dehydration: drinks eagerly, thirsty, restless, irritable, sunken eyes, or skin pinch goes back slowly.

Children with severe dehydration are usually lethargic, in a stupor, or even in a coma. Symptoms are even more apparent (deeply sunken eyes without tears, very dry mouth and tongue, rapid and deep breathing). A skin pinch retracts very slowly (over two seconds). Children who are awake are very thirsty, although a child may drink poorly if in a stupor. A child may not have urinated for six hours or longer. When in hypovolemic shock, systolic blood pressure taken in the arm is low or not detectable, the arms and legs are cool, and the nail beds may have a bluish or purplish discoloration. Two of the following symptoms indicate severe dehydration: lethargic or unconscious, very slow skin pinch, sunken eyes, and not able to drink or drinking poorly.

Dehydration can cause confusion, constipation , discomfort, drowsiness, and fever. The skin turns pale and cold, the mucous membranes lining the mouth and nose lose their natural moisture. The pulse sometimes races and breathing becomes rapid. Significant fluid loss can cause serious neurological problems or death.

When to call the doctor

A doctor should be notified whenever an infant or child exhibits signs of dehydration or a parent is concerned that a stomach virus or other acute illness may lead to dehydration.

A doctor should also be notified if any of the following is the case:

  • Symptoms of dehydration worsen.
  • A breast-fed or bottle-fed infant is unable to feed or feeds poorly.
  • An infant or child urinates very sparingly or does not urinate at all during a eight-hour period.
  • An infant younger than two months of age has diarrhea or is vomiting.
  • Dizziness, listlessness, or excessive thirst occurs.
  • The child's heart is beating fast.
  • The child has dry eyes, sunken eyes, a dry mouth, or is not producing tears.
  • There is blood in the stool or vomit.

An infant can become dehydrated within hours after the onset of illness. In general, the smaller the child, the lower the threshold should be for healthcare intervention if dehydration is suspected.

Diagnosis

A child's symptoms and medical history alone usually suggest dehydration. Physical symptoms are usually all that is necessary for diagnosing dehydration, although laboratory tests may be ordered by the physician. Physical examination may reveal shock, rapid heart rate, and/or low blood pressure. Laboratory tests, including blood tests (to check electrolyte levels) and urine tests (e.g. urine specific gravity and creatinine), may be used to evaluate the severity of the problem.

Treatment

Increased fluid intake and replacement of lost electrolytes are extremely important for restoring fluid balances in infants and children who are dehydrated. Treatment is given based on severity of dehydration. Treatment should include two phases: a rehydration phase and a maintenance phase. In the rehydration phase, fluid losses are replaced quickly, within three to four hours until normal hydration is achieved. In the maintenance phase, calories and fluids are given. Rapid refeeding should follow rapid rehydration with the goal of returning the child to an unrestricted, age-appropriate diet including solids. Withholding foods to rest the gut is not recommended. Breastfeeding should be continued at all times through both stages of treatment. Full-strength formula is usually tolerated. Changing formula or diluting to half strength are common practices but are usually unnecessary and may even prolong symptoms and delay nutritional recovery.

To replace calories quickly during acute illness, food should be given as soon as the child will tolerate it. During both rehydration and maintenance phases, fluid losses from vomiting and diarrhea should be replaced continuously. Restricting lactose (milk and milk products) is usually not necessary but may be helpful in a child with a severe intestinal disease or diarrhea in a malnourished child.

Children with minimal dehydration weighing less than 10 kilograms (22 pounds) should be given 60 to 120 mL (24 ounces) of an oral rehydration solution (ORS) for each episode of vomiting or diarrheal stool. Those weighing more than 10 kg (22 lbs) should be given 120 to 240 mL (48 ounces). Food should not be restricted. Children with mild to moderate dehydration should be given 50 to 100 mL (roughly 23.5 ounces) of an ORS per kilogram body weight during two to four hours to replace fluid losses. Additional ORS should be administered to replace ongoing losses from vomiting and diarrhea. In a sick child, a teaspoon, syringe, or medicine dropper can be used to offer a small amount at first with amounts increasing as tolerated. If the child appears to want more, more can be given. Severe dehydration is a medical emergency requiring intravenous fluids immediately.

For moderate or severe dehydration, a child should be treated in a medical facility. Moderate dehydration can be treated orally, but severe dehydration requires the child to take fluids intravenously (IV). When treating dehydration, the underlying cause must also be addressed. For example, if dehydration is caused by vomiting, medications may be prescribed to resolve these symptoms. However, anti-diarrheal medications are not recommended in children. A child who is dehydrated due to diabetes, kidney disease, or adrenal gland disorders must receive treatment for these conditions as well as for the resulting dehydration.

For older children who are mildly dehydrated, just drinking plain water may be all the treatment that is needed. For infants and younger children, especially when ill, drinking a commercial ORS should be encouraged. Parents should follow label instructions when giving children Pedialyte or other commercial products recommended for relieving dehydration. Sports drinks are not recommended as they contain a lot of sugar and may worsen diarrhea.

In order to accurately calculate fluid loss, it is important to chart weight changes every day and keep a record of how many times a child vomits or has diarrhea. Parents should note how many times a baby's diaper must be changed.

Alternative treatment

Gelatin water may be substituted for electrolyte-replacement solutions if an ORS is unavailable. It is made by diluting a 3-oz package in a quart of water or by adding one-fourth teaspoon of salt and a tablespoon of sugar to a pint of water. Receiving the right amount of electrolytes is very important, and thus homemade remedies such as gelatin (or adding salt or sugar to water) are not recommended because of the potential for quantity errors when mixing. However, these may be useful if ORS cannot be obtained in an emergency. Parents should keep a can of ORS on hand for emergencies.

Formulas containing soy fiber have been reported to reduce liquid stools.

Prognosis

Mild dehydration rarely results in complications. If the cause is eliminated and lost fluid is replaced, mild dehydration can usually be cured quickly.

Vomiting and diarrhea that continue for several days without adequate fluid replacement can be fatal. However, dehydration that is rapidly recognized and treated has a good outcome.

Prevention

Ensuring that children always drink adequate fluids during an illness helps to prevent dehydration. Parents can prevent dehydration in infants and children who are vomiting or who have diarrhea by increasing fluids to compensate for losses. Infants and children with diarrhea and vomiting should be given ORS such as Pedialyte immediately to help prevent dehydration.

Children who are not ill can maintain proper fluid balance by drinking water or fluids even before they are thirsty. Children should drink fluids before going outside to exercise or play (especially on a hot day). Dehydration can usually be prevented by drinking enough fluid for urine to remain the color of pale straw. Water in foods, especially fruits and vegetables, is a great source of fluid. Fruits and vegetables can contain up to 95 percent water, so a well-balanced diet is a good way to stay hydrated.

Parents should know whether any medication their child is taking can cause dehydration and should get prompt medical care to correct any underlying condition that increases the risk of dehydration.

Other methods of preventing dehydration and ensuring adequate fluid intake are as follows:

  • eating more soup at mealtime
  • drinking plenty of water and juice at mealtime and between meals
  • keeping a glass of water nearby

Children should not be given coffee or tea, because they increase body temperature and water loss. Avoiding caffeinated soft drinks may also reduce the risk of dehydration. These beverages are all diuretics (substances that increase fluid loss).

KEY TERMS

Diuretic A group of drugs that helps remove excess water from the body by increasing the amount lost by urination.

Electrolytes Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Resources

BOOKS

Batmanghelidj, F. Water: For Health, For Healing, For Life: You're Not Sick, You're Thirsty! New York: Warner Books, 2003.

Kleinman, Ronald E., and the American Academy of Pediatrics Committee on Nutrition. Pediatric Nutrition Handbook, 5th ed. Elk Grove Village, IL: American Academy of Pediatrics, 2003.

Physicians Committee for Responsible Medicine. Healthy Eating for Life for Children. Hoboken, NJ: Wiley, 2002.

Speakman, Elizabeth, and Norma Jean Weldy. Body Fluids and Electrolytes, 8th ed. London: Mosby Incorporated, 2001.

Willett, Walter C., and P. J. Skerrett. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. New York: Simon & Schuster Source, 2002.

Workman, M. Linda. Introduction to Fluids, Electrolytes and Acid-Base Balance. London: Saunders, 2001.

PERIODICALS

Steiner, M. J., et al. "Is this child dehydrated?" Journal of the American Medical Association 291, no. 22 (June 2004): 274654.

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 600071098. Web site: <www.aap.org>.

American College of Emergency Physicians. 1125 Executive Circle, Irving, TX 750382522. Web site: <www.acep.org>.

WEB SITES

Rehydration Project. Available online at <www.rehydrate.org> (accessed November 16, 2004).

"Why Is Dehydration so Dangerous?" Rehydration Project. Available online at <www.rehydrate.org/dehydration/index.html> (accessed November 16, 2004).

Crystal Heather Kaczkowski, MSc. Maureen Haggerty

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Dehydration

Dehydration

Definition

Dehydration is the loss of water and salts essential for normal body function.

Description

Dehydration occurs when the body loses more fluid than it takes in. This condition can result from illness; a hot, dry climate; prolonged exposure to sun or high temperatures; not drinking enough water; and overuse of diuretics or other medications that increase urination. Dehydration can upset the delicate fluid-salt balance needed to maintain healthy cells and tissues.

Water accounts for about 60% of a man's body weight. It represents about 50% of a woman's weight. Young and middle-aged adults who drink when they're thirsty do not generally have to do anything more to maintain their body's fluid balance. Children need more water because they expend more energy, but most children who drink when they are thirsty get as much water as their systems require.

Age and dehydration

Adults over the age of 60 who drink only when they are thirsty probably get only about 90% of the fluid they need. Developing a habit of drinking only in response to the body's thirst signals raises an older person's risk of becoming dehydrated. Seniors who have relocated to areas where the weather is warmer or dryer than the climate they are accustomed to are even likelier to become dehydrated unless they make it a practice to drink even when they are not thirsty.

Dehydration in children usually results from losing large amounts of fluid and not drinking enough water to replace the loss. This condition generally occurs in children who have stomach flu characterized by vomiting and diarrhea, or who can not or will not take enough fluids to compensate for excessive losses associated with fever and sweating of acute illness. An infant can become dehydrated only hours after becoming ill. Dehydration is a major cause of infant illness and death throughout the world.

Types of dehydration

Mild dehydration is the loss of no more than 5% of the body's fluid. Loss of 5-10% is considered moderate dehydration. Severe dehydration (loss of 10-15% of body fluids) is a life-threatening condition that requires immediate medical care.

Complications of dehydration

When the body's fluid supply is severely depleted, hypovolemic shock is likely to occur. This condition, which is also called physical collapse, is characterized by pale, cool, clammy skin; rapid heartbeat; and shallow breathing.

Blood pressure sometimes drops so low it can not be measured, and skin at the knees and elbows may become blotchy. Anxiety, restlessness, and thirst increase. After the patient's temperature reaches 107 °F (41.7 °C) damage to the brain and other vital organs occurs quickly.

Causes and symptoms

Strenuous activity, excessive sweating, high fever, and prolonged vomiting or diarrhea are common causes of dehydration. So are staying in the sun too long, not drinking enough fluids, and visiting or moving to a warm region where it doesn't often rain. Alcohol, caffeine, and diuretics or other medications that increase the amount of fluid excreted can cause dehydration.

Reduced fluid intake can be a result of:

  • appetite loss associated with acute illness
  • excessive urination (polyuria)
  • nausea
  • bacterial or viral infection or inflammation of the pharynx (pharyngitis)
  • inflammation of the mouth caused by illness, infection, irritation, or vitamin deficiency (stomatitis)

Other conditions that can lead to dehydration include:

  • disease of the adrenal glands, which regulate the body's water and salt balance and the function of many organ systems
  • diabetes mellitus
  • eating disorders
  • kidney disease
  • chronic lung disease.

An infant who does not wet a diaper in an eight-hour period is dehydrated. The soft spot on the baby's head (fontanel) may be depressed. Symptoms of dehydration at any age include cracked lips, dry or sticky mouth, lethargy, and sunken eyes. A person who is dehydrated cries without shedding tears and does not urinate very often. The skin is less elastic than it should be and is slow to return to its normal position after being pinched.

Dehydration can cause confusion, constipation, discomfort, drowsiness, fever, and thirst. The skin turns pale and cold, the mucous membranes lining the mouth and nose lose their natural moisture. The pulse sometimes races and breathing becomes rapid. Significant fluid loss can cause serious neurological problems.

Diagnosis

The patient's symptoms and medical history usually suggest dehydration. Physical examination may reveal shock, rapid heart rate, and/or low blood pressure. Laboratory tests, including blood tests (to check electrolyte levels) and urine tests (e.g., urine specific gravity and creatinine), are used to evaluate the severity of the problem. Other laboratory tests may be ordered to determine the underlying condition (such as diabetes or an adrenal gland disorder) causing the dehydration.

Treatment

Increased fluid intake and replacement of lost electrolytes are usually sufficient to restore fluid balances in patients who are mildly or moderately dehydrated. For individuals who are mildly dehydrated, just drinking plain water may be all the treatment that is needed. Adults who need to replace lost electrolytes may drink sports beverages (e.g., Gatorade or Recharge) or consume a little additional salt. Parents should follow label instructions when giving children Pedialyte or other commercial products recommended to relieve dehydration. Children who are dehydrated should receive only clear fluids for the first 24 hours.

A child who is vomiting should sip one or two teaspoons of liquid every 10 minutes. A child who is less than a year old and who is not vomiting should be given one tablespoon of liquid every 20 minutes. A child who is more than one year old and who is not vomiting should take two tablespoons of liquid every 30 minutes. A baby who is being breast-fed should be given clear liquids for two consecutive feedings before breastfeeding is resumed. A bottle-fed baby should be given formula diluted to half its strength for the first 24 hours after developing symptoms of dehydration.

In order to accurately calculate fluid loss, it's important to chart weight changes every day and keep a record of how many times a patient vomits or has diarrhea. Parents should note how many times a baby's diaper must be changed.

Children and adults can gradually return to their normal diet after they have stopped vomiting and no longer have diarrhea. Bland foods should be reintroduced first, with other foods added as the digestive system is able to tolerate them. Milk, ice cream, cheese, and butter should not be eaten until 72 hours after symptoms have disappeared.

Medical care

Severe dehydration can require hospitalization and intravenous fluid replacement. If an individual's blood pressure drops enough to cause or threaten the development of shock, medical treatment is usually required. A doctor should be notified whenever an infant or child exhibits signs of dehydration or a parent is concerned that a stomach virus or other acute illness may lead to dehydration.

a doctor should also be notified if:

  • a child less than three months old develops a fever higher than 100 °F (37.8 °C)
  • a child more than three months old develops a fever higher than 102 °F (38.9 °C)
  • symptoms of dehydration worsen
  • an individual urinates very sparingly or does not urinate at all during a six-hour period
  • dizziness, listlessness, or excessive thirst occur
  • a person who is dieting and using diuretics loses more than 3 lb (1.3 kg) in a day or more than 5 lb (2.3 kg) a week

When treating dehydration, the underlying cause must also be addressed. For example, if dehydration is caused by vomiting or diarrhea, medications may be prescribed to resolve these symptoms. Patients who are dehydrated due to diabetes, kidney disease, or adrenal gland disorders must receive treatment for these conditions as well as for the resulting dehydration.

Alternative treatment

Gelatin water can be substituted for electrolyte-replacement solutions. It is made by diluting a 3-oz package in a quart of water or by adding one-quarter teaspoon of salt and a tablespoon of sugar to a pint of water.

Prognosis

Mild dehydration rarely results in complications. If the cause is eliminated and lost fluid is replaced, mild dehydration can usually be cured in 24-48 hours.

Vomiting and diarrhea that continue for several days without adequate fluid replacement can be fatal. The risk of life-threatening complications is greater for young children and the elderly. However, dehydration that is rapidly recognized and treated has a good outcome.

Prevention

Patients who are vomiting or who have diarrhea can prevent dehydration by drinking enough fluid for their urine to remain the color of pale straw. Ensuring that patients always drink adequate fluids during an illness will help prevent dehydration. Infants and young children with diarrhea and vomiting can be given electrolyte solutions such as Pedialyte to help prevent dehydration. People who are not ill can maintain proper fluid balance by drinking several glasses of water before going outside on a hot day. It is also a good idea to avoid coffee and tea, which increase body temperature and water loss.

Patients should know whether any medication they are taking can cause dehydration and should get prompt medical care to correct any underlying condition that increases the risk of dehydration.

Other methods of preventing dehydration and ensuring adequate fluid intake include:

  • eating more soup at mealtime
  • drinking plenty of water and juice at mealtime and between meals
  • keeping a glass of water nearby when working or relaxing

Resources

OTHER

"HydrationGetting Enough Water." Loyola University Health System. May 13, 1998. http://www.luhs.org.

KEY TERMS

Electrolytes Mineral salts, such as sodium and potassium, dissolved in body fluid.

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Dehydration

Dehydration

Dehydration is the excessive loss of water from the body. Water can be lost through urine, sweat, feces, respiration, and through the skin. Symptoms of dehydration in order of severity are: thirst, nausea , chills, clammy skin, increased heart rate, muscle pain, reduced sweating, dizziness, headache, shortness of breath, dry mouth, fatigue , lack of sweating, hallucinations, fainting, and loss of consciousness. Dehydration can affect mental alertness, renal function, circulation, and total physical capacity.

The following can help to avoid dehydration:

  1. Drink before feeling thirsty
  2. Drink enough fluid to have pale yellow urine
  3. Avoid caffeine and alcohol, which act as diuretics
  4. Drink two to three cups of fluid two hours before exercise or heavy outside work in hot temperatures
  5. Drink one to two cups of fluid every fifteen minutes during exercise or heavy outside work in hot temperatures
  6. Avoid exercising during midday heat, and wear appropriate clothing that allows airflow around the body

Athletes, elderly persons, young children, and those with specific illnesses that affect fluid balance, such as severe diarrhea, are at higher risk for dehydration than the average person.

see also Malnutrition; Oral Rehydration Therapy; Sports Nutrition.

Mindy Benedict

Bibliography

Dorland's Pocket Medical Dictionary, 23d edition (1982). Philadelphia: W. B. Saunders.

Berning, Jacqueline R., and Steen, Suzanne Nelson (1998). Nutrition for Sport and Exercise, 2nd edition. Gaithersburg, MD: Aspen.

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dehydration

dehydration Removal or loss of water from a substance or tissue. Water molecules can be removed by heat, catalysts or a dehydrating agent such as concentrated sulphuric acid. Dehydration is used in food preservation, such as the freeze-drying process of such items as coffee and meat. In medicine, excessive water loss is often a symptom or result of disease or injury.

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dehydration

dehydration Removal of water, especially from a chemical compound by heat, sometimes in the presence of a catalyst or dehydrating agent, e.g. sulphuric acid. Also refers to removal of water from crystals, oil, etc., commercially by distillation, chemicals, or heat. In metamorphism, prograde metamorphic reactions commonly involve dehydration of hydrous minerals.

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dehydration

dehydration The removal of water, especially from a chemical compound by heat, sometimes in the presence of a catalyst or dehydrating agent (e.g. sulphuric acid), or the removal of water from crystals, oil, etc., commercially by distillation, chemicals, or heat.

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dehydration

dehydration (dee-hy-dray-shŏn) n. loss or deficiency of water in body tissues. The condition may result from inadequate water intake and/or from excessive removal of water from the body; for example, by sweating, vomiting, or diarrhoea.

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dehydration

dehydration Drying, normally used for factory‐dried, as distinct from wind‐dried, materials.

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Dehydration

Dehydration

Definition

Dehydration is the excessive loss of water from body tissues accompanied by an imbalance in essential electrolytes, such as sodium, potassium, and chloride.

Description

Dehydration occurs when the body loses more fluid than it takes in. Dehydration can be caused by illness, injury, infection, prolonged exposure to sun or high temperatures, inadequate water intake, or over-use of diuretics or other medications that increase urination.

Water is distributed throughout three compartments in the body: inside the cells (intracellular), in the tissue (interstitial), and in the bloodstream (intravascular). Each compartment contains differing amounts of electrolytes that must remain in balance in order for body organs and systems to function correctly. Dehydration upsets this delicate balance. Total body water also varies in relation to age, gender, and amount of body fat. Adult males have approximately 60% water content, adult females have 50%, infants have an estimated 77%, and the elderly have 46% to 52%. An increase in body fat causes a decrease in the percent fluid content because fat does not contain significant amounts of water.

Causes and symptoms

Different types of dehydration have different causes. When managing patients with dehydration, the type of water loss must be determined to ensure appropriate treatment. In addition, water and sodium levels in the body are closely related; if one is abnormal, the other often is too.

Isotonic dehydration is an equal loss of water and sodium. Isotonic means that the number of particles contained on one side of a permeable membrane is the same as on the other side, thus there is no fluid shift in either direction. The amount of intracellular and extracellular water remains in balance. This can be caused by a complete fast, vomiting, and diarrhea.

Hypertonic dehydration occurs when water loss is greater than sodium loss. Blood sodium levels may be > 145 mmol/l (normal range = 135 to 145 mmol/l). Higher blood sodium levels combined with decreased water in the intravascular space increases the osmotic pressure in the bloodstream, which, in turn, pulls more fluid out of the cells. This type of dehydration is usually caused by extended fever with limited oral rehydration. Mortality is more likely to occur from hypertonic than from isotonic dehydration.

Hypotonic dehydration occurs when sodium loss is greater than water loss. Blood sodium levels may be less than 135 mmol/l; and the osmotic pressure is greater inside the cells, which pulls more fluid out of the intravascular space into the intracellular space. This type of dehydration occurs with overuse of diuretics, which causes excessive sodium and potassium loss. Potassium depletion affects respiration, increases nausea, and, if severe enough, may cause respiratory arrest or central nervous system (CNS) seizures. Potassium depletion may also cause arrhythmias (an alteration in the heartbeat). As a result, patients are told to take diuretics with orange juice or to eat a banana, both of which are high in potassium.

Strenuous activity, excessive sweating, prolonged time in the sun, and extended vomiting or diarrhea cause fluid loss. Elderly people who move to warm, dry climates frequently become dehydrated because of the climate change combined with a tendency to not drink enough water. Large amounts of fluid can also be lost from prolonged fever. Healthy people require about 1 milliliter of water for each calorie their body metabolizes; but during a fever the metabolic rate increases by seven percent for each 1 F rise in body temperature. Fever also increases the respiratory rate, resulting in additional water loss from the lungs. Further causes of fluid loss that may be overlooked include caffeine and alcohol consumption, which increase urination and fluid excretion.

Decreased oral intake of fluids is a common cause of dehydration and often occurs during times of appetite loss from illness or after oral surgery or injury. The elderly are at high risk for decreased intake because their thirst mechanism may no longer function or they may be physically unable to get a drink. Infants, another high-risk group, are more likely to develop dehydration than adults because they have a higher metabolic rate and their immature kidneys have difficulty concentrating urine. Children who do not wet their diapers for three hours or more are dehydrated. Dehydration is also associated with disorders of the adrenal glands, which regulate water-electrolyte balance; diabetes mellitus; eating disorders; renal disease; and chronic lung disease.

Symptoms of dehydration at any age may include some or all of the following: cracked lips, dry or sticky mucous membranes, sunken eyes, lethargy, and/or confusion. Urine output is minimal and the skin loses its elasticity (turgor) and is slow to return to its normal position after being raised off the back of the hand (tenting). The heart rate and respiratory rate may be elevated. A dehydrated infant may not shed tears when crying and may have a depressed fontanel (soft spot on their head), although recent studies have shown that a depressed fontanel is not an accurate indicator of dehydration.

Diagnosis

The general diagnosis of dehydration can be made based on the patient's symptoms and medical history. Physical examination may reveal any of the symptoms mentioned above, along with shock, rapid heart rate, and low blood pressure. Blood tests are required to determine what deficiency exists (or what is elevated) so that therapy for electrolyte replacement can be planned. Blood tests to check electrolyte levels and urine tests such as urine specific gravity are used to evaluate the severity of the fluid loss. Other laboratory tests may be ordered to determine if an underlying condition (e.g., diabetes or an adrenal gland disorder) is the cause.

Treatment

Increased fluid intake and replacement of lost electrolytes are usually sufficient to restore fluid balance in patients who are mildly or moderately dehydrated. For individuals who are mildly dehydrated, just drinking plain water may be all the treatment that is needed. Adults may replace lost electrolytes by drinking sports beverages, such as Gatorade or Recharge. Parents should follow label instructions when giving children Pedialyte or other commercial products recommended for the treatment of dehydration in children. Children who are dehydrated should be given only clear fluids for the first 24 hours.

A child who is vomiting should sip one or two teaspoons of liquid every 10 minutes. A child who is less than a year old and who is not vomiting should be given one tablespoon of liquid every 20 minutes. A child who is more than one year old and who is not vomiting should take two tablespoons of liquid every 30 minutes. A baby who is being breast-fed should be given clear liquids for two consecutive feedings before breastfeeding is resumed. A bottle-fed baby should be given formula diluted with water to half the formula strength for the first 24 hours after symptoms of dehydration are identified.

To calculate fluid loss accurately, weight changes should be charted every day and a record kept of how many times a patient vomits or has diarrhea. A record of fluid output (including sputum or vomit) and of fluid intake or replacement should be kept for at least 24 to 48 hours to see if balance is being accomplished. Parents should note how many times a baby's diaper must be changed. If dehydration continues, emergency department treatment or hospitalization to receive intravenous fluids and electrolytes may be necessary.

Children and adults can gradually return to their normal diet after they have stopped vomiting and no longer have diarrhea. Gelatin is often a welcomed substitute for additional water and does count as fluid replacement. Bland foods should be reintroduced first, with other foods added as the digestive system is able to tolerate them. Milk, ice cream, cheese, and butter should not be eaten until 72 hours after symptoms have disappeared.

When treating dehydration, the underlying cause must be addressed. For example, if dehydration is caused by vomiting or diarrhea, medications should be prescribed to resolve these symptoms. Patients who are dehydrated due to diabetes, kidney disease, or adrenal gland disorders must receive treatment for these conditions as well as for the resulting dehydration. If dehydration is being caused by diuretics, a dose adjustment made by the physician or a change to a different diuretic may be necessary.

Prognosis

Mild dehydration rarely results in complications. If the cause is eliminated and lost fluid is replaced, mild dehydration can usually be resolved in 24 to 48 hours. Vomiting and diarrhea that continue for several days without adequate fluid replacement can be fatal since more is lost than water and sodium. Severe potassium loss may lead to cardiac arrhythmias, respiratory distress or arrest, or convulsions (seizures). The risk of life-threatening complications is greater for young children and the elderly. However, dehydration that is rapidly recognized and treated has a good outcome.

Health care team roles

The nurse and the physician have the greatest responsibility in recognizing and treating dehydration. For hospitalized patients, the physician should order appropriate fluid and electrolyte replacement and the nurse should ensure that the correct fluids are given to the patient. The nurse should monitor the patient for signs that the dehydration (e.g., decrease in fever, increase in blood pressure, reduced heart rate) is resolving and should notify the physician if it is not.

Blood tests used to diagnose dehydration are collected by specially trained nursing assistants or by laboratory technicians. Outpatient samples in a physician's office may be taken by the nurse or a technician. In some institutions, the nurse collects the blood sample. Usually, urine samples are collected by the nurse, and results calculated by the laboratory technician.

Prevention

Patients who are vomiting or who have diarrhea can prevent dehydration by drinking enough fluid to keep their urine the color of pale straw. Infants and young children with diarrhea and vomiting can be given electrolyte solutions such as Pedialyte to help prevent dehydration, as well as suppository medication to stop the vomiting. People who are not ill can maintain proper fluid balance by drinking several glasses of water before going outside on a hot day. It is also a good idea to avoid coffee and tea, which increase body temperature and water loss.

KEY TERMS

Extracellular— Outside the cells.

Hypertonic— One solution having a greater amount of solute (dissolved substance in a solution) than another solution, thus it exerts more osmotic pressure than the second solution and the body will attempt to equalize pressure by passing fluid through the cell membranes.

Hypotonic— One solution having a lesser amount of solute than another solution, thus it exerts less osmotic pressure than the second solution.

Intracellular— Inside the cells.

Isotonic— Two solutions exerting the same amount of osmotic pressure on a cell membrane.

Osmotic pressure— The pressure exerted on a semipermeable membrane that separates two solutions and the particles they contain.

Patients should ask a pharmacist whether or not any medications they are taking may cause dehydration and what to do to prevent it other than adequate fluid intake. Prompt medical attention should be sought to correct any underlying condition that increases the risk of dehydration.

Resources

BOOKS

Andreoli, Thomas E., et al., eds. Cecil Essentials of Medicine, 5th ed. Philadelphia, PA: W.B. Saunders Company, 2001.

Porth, C. Pathophysiology: Concepts of Altered Health States. Philadelphia, PA: Lippincott, 1998.

Rakel, Robert E., ed. Conn's Current Therapy 2000. Philadelphia, PA: W.B. Saunders Company, 1999.

Thelan, Lynne, et al. Critical Care Nursing: Diagnosis and Management. St. Louis, MO: Mosby, 1998.

PERIODICALS

Pace, B. "Preventing Dehydration from Diarrhea." JAMA 285, no. 3 (2001): 362.

Sullivan, A. "Hydration for Adults." Nursing Standard 14, no. 8 (1999): 44-46.

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Dehydration

Dehydration

Definition

Description

Demographics

Causes and symptoms

Diagnosis

Treatment

Nutrition/Dietetic concerns

Prognosis

Prevention

Resources

Definition

Dehydration is a condition in which the body looses too much water usually as a result of excess sweating, vomiting, and/or diarrhea.

Signs of dehydration

General dehydration

  • Thirst
  • Less frequent urination
  • Dry skin
  • Fatigue
  • Light-headedness
  • Dark colored urine

Dehydration in children

  • Dry mouth and tongue
  • No tears when crying
  • No wet diapers for 3 hours or more
  • Sunken abdomen, eyes, or cheeks
  • High fever
  • Listlessness or irritability
  • Skin that does not flatten when pinched and released

source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services.

(Illustration by GGS Information Services/Thomson Gale.)

Description

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.

KEY TERMS

Diabetes— a condition in which the body either does not make or cannot respond to the hormone insulin. As a result, the body cannot use glucose (sugar). There are two types, type 1 and type 2.

Diuretic— a substance that removes water from the body by increasing urine production.

Electrolyte— ions in the body that participate in metabolic reactions. The major human electrolytes are sodium (Na+), potassium (K+), calcium (Ca 2+), magnesium (Mg2+), chloride (Cl-), phosphate (HPO4 2-), bicarbonate (HCO3-), and sulfate (SO4 2-).

Laxative— A substance that stimulates movement of food through the bowels. Laxatives are used to treat constipation.

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. Electrolytes are 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.

Demographics

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.

Certain chronic illnesses that disrupt fluid balance can cause dehydration. Kidney disease and hormonal disorders, such as diabetes, adrenal gland, or pituitary gland disorders, can cause fluid and electrolyte loss through excessive urination. Disorders such as cystic fibrosis or other genetic disorders resultING in inadequate absorption of nutrients from the intestines can cause chronic diarrhea that leads to dehydration. Individuals with eating disorders who abuse laxatives, diuretics , and enemas, or regularly cause themselves to vomit are vulnerable to severe electrolyte imbalances and dehydration. The same is true of people with alcoholism. People who have severe burns over a large part of their body also are likely to become dehydrated because they no longer have skin to act as a barrier to evaporation.

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.

Diagnosis

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.

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).

Nutrition/Dietetic concerns

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.

Prognosis

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.

Prevention

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.

Resources

BOOKS

Batmanghelidj, F. Water: For Health, for Healing, for Life: You’re Not Sick, You’re Thirsty!.New York: Warner Books, 2003.

Panel on Dietary Reference Intakes for Electrolytes and Water, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board. DRI, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academies Press, 2005.

PERIODICALS

Wellbery, Caroline. “Diagnosing Dehydration in Children.” American Family Physician. 71 no.5 (March 1, 2005):1010.

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Blvd. Elk Grove Village, IL 60007. Telephone: (847) 434-4000. Website: <http://www.aap.org>

American College of Sports Medicine. 401 West Michigan Street, Indianapolis, IN 46202. Telephone: (317) 637-9200. Fax: (317) 634-7871. Website: <http://www.ascm.org.>

OTHER

Ellsbury, Dan E. and Catherine S. George. “Dehydration.” eMedicine.com, March 30, 2006. <http://www.emedicine.com/ped/topic556.htm>

Kenney, Larry. “Dietary Water and Sodium Requirements for Active Adults.” Sports Science Exchange 92.17, no.1 (2004) <http://www.gssiweb.com/Article_Detail.aspx?articleID=667>

Murray, Robert. “The Risk and Reality of Hyponatremia.” Gatorade Sports Science Institute, 2006.<http://www.gssiweb.com/>

Mayo Clinic Staff. “Dehydration.” MayoClinic.com, January 3, 2007. <http://www.mayoclinic.com/health/dehydration/DS00561>

Medline Plus. “Dehydration.” U. S. National Library of Medicine, April 5, 2007. <http://www.nlm.nih/gov/medlineplus/ency/article/000982.htm.html>

Tish Davidson, A.M.

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Dehydration

Dehydration

Definition

Dehydration is the condition of the body when fluid loss is greater than fluid intake. Hydration describes a condition of fluid balance (water homeostasis) when adequate fluid levels are maintained. When fluid balance is not maintained, the individual is said to be dehydrated.

Description

All people of all ages must drink fluids every day to ensure proper performance of normal body functions. Drinking only when feeling thirsty is not enough to replace fluid lost through normal urination, sweating (perspiration), and engaging in physical exercise . The body and bloodstream are composed of fluid and every cell, tissue, and organ in the body requires a certain amount of fluid in order to function. When people drink water or other liquids, the fluid passes through the mouth, throat, esophagus, and stomach, into the intestines, and then into the

(Illustration by GGS Information Services. Cengage Learning, Gale.)
Symptoms of dehydration
  • Constipation
  • Dark urine (may have a strong odor)
  • Decreased or absent urine output
  • Dizziness
  • Dry lips and mouth
  • Dry nasal passages
  • Fatigue
  • General weakness
  • Headache
  • Loose skin (lacking elasticity)
  • Muscle weakness or cramps
  • Sunken eyes
Symptoms of severe dehydration
  • Falling down
  • Irritability
  • Kidney and urinary tract infections
  • Mental confusion
  • Rapid pulse and heart beat
  • Rapid weight loss
  • Sudden drops in blood pressure

bloodstream, carrying nourishment for the whole body and helping to maintain body temperature.

Amounts of fluid lost by each individual varies depending on age, overall health, and amount of physical activity. In young and middle-aged adults, total body water is about 50 to 60 % total body water decreases in senior adults to about 50%of body weight. Typical fluid replacement in a healthy adult should consist of about eight glasses of water (or other clear fluids) each day, enough to equal about a third of body weight. People who are more physically active require even more replacement fluid. Drinking less than eight glasses of water can result in a mildly dehydrated state that will likely go unnoticed, but excessive loss of water from the body through excess urination, strenuous exercise, diarrhea , vomiting, high fever, or certain gastrointestinal or kidney disorders is enough to cause noticeable symptoms of dehydration and sometimes severe, life-threatening dehydration.

Athletes are at risk of dehydration when excess fluid is lost in sweating during physical exertion. Children are at high risk because their percentage of water per body weight is lower than in bodies with larger frames, and yet their bodies actually use more water. Risk is highest in senior adults because replacement of lost fluid is more difficult in the presence of underlying illnesses, including diabetes, kidney disease, heart disease and gastrointestinal diseases, as well as a host of reasons they may have for not drinking enough, including difficulty getting up from resting positions to go to the bathroom and fear of accidents when the ability to control urination has been lost (incontinence).

Dehydration occurs more frequently in senior adults because of changes due to aging. A healthy body normally has its own ways to protect against losing too much water, but in senior adults these functions are often reduced or compromised by disease conditions. Fluid-related changes due to aging include: 1) the body's way of triggering thirst is less sensitive as people age, which reduces desire to drink fluid, 2) a lower percentage of body weight is composed of water in older individuals and dehydration can occur more rapidly, and 3) aging kidneys are less able to concentrate urine and excrete the water load.

The body's use of water and the effects of water loss on body function is a highly complex process. Important to this process are levels of body chemicals called electrolytes, which are present in body fluid and essential for proper functioning of the heart, muscles, brain, nervous system, and for regulating fluid balance and maintaining hydration. Electrolytes, including Dehydration sodium , potassium, chloride, and bicarbonate, among others, carry electrical signals that aid communication within cells and between organ systems. Amounts of electrolytes must be balanced to maintain critical functions of cells and organs. Because electrolytes are also involved in helping to regulate amounts of fluid inside and outside of body cells, changes in fluid balance that occur with excess losses or poor replacement also upset electrolyte balance and the specific functions electrolytes control. Sodium is present in fluid outside of body cells (extra-cellular sodium) and plays a significant role in regulating total fluid levels, which, in turn, affects blood pressure , heart function and other functions. Potassium inside of cells (intra-cellular potassium) aids cell functioning and helps regulate heart beat and muscle contraction. Bicarbonate helps balance acidity and alkalinity (pH) of the blood and other body fluids. At the cellular level, sodium, potassium, and chloride influence urinary output, fluid retention, fluid loss and thirst, making balance between these electrolytes extremely important. When there are fluid losses, electrolytes are lost too, leading to complications. The reverse is also true; if electrolyte levels change because of medications, diet (e.g., excess consumption of salt, which is sodium chloride), or diseases (e.g., increased chloride with kidney disease or overactive thyroid), changes in fluid level occur. Even mild dehydration must be treated in order to avoid critical imbalances in fluid and electrolyte levels that can change the way essential body processes are carried out, sometimes resulting in serious consequences such as organ dysfunction or failure.

Demographics

Dehydration can occur among all populations. Older adults (over age 65) are at greatest risk of dehydration, which is a frequent cause of hospitalization among this age group. Senior adults at greatest risk of dehydration include those who have the following characteristics:

  • are over age 85
  • live alone and do not drink enough or have access to fluids
  • over-consume alcohol
  • take medications such as diuretics, laxatives, and sedatives
  • have acute or chronic illness that affects normal eating and drinking habits
  • are confused or have mental problems or communication problems
  • have difficulty swallowing

Causes and symptoms

The cause of dehydration is always loss of fluid and lack of replacement. It results from not taking in enough fluid to replace normal losses through urination, sweating, and exercise. It can also happen when excess fluid is lost in illnesses that increase urinary output or cause vomiting, diarrhea, or high fever. Physical exertion that results in excessive sweating may dehydrate the body. Bleeding (e.g., gastrointestinal bleeding), infection, or draining of open wounds can reduce fluid levels, also. Taking certain medications may also cause dehydration, especially diuretics that are used to remove excess fluid from the circulation of people with blood pressure and heart problems. Individuals who have severe burns lose excess fluids through the loss of tissue, and dehydration in this case can be severe and life-threatening.

Common symptoms of dehydration are dry lips and mouth, dry nasal passages, sunken eyes, loose skin, headache, fatigue, muscle cramps, dizziness , and general weakness. Decreased amounts of urine and reduced frequency of urination may also occur, but the affected person may not pay attention to urine output. Constipation can also be a symptom of dehydration; it may occur when not enough fluid is available to help move waste through the intestines. Rapid weight loss may be an important sign of serious dehydration, as well as development of kidney and urinary tract infections, mental confusion, falling down, irritability, rapid pulse and heart beat (100 or more beats per minute), and sudden drops in blood pressure when rising from sitting to a standing position (postural or orthostatic hypotension).

Diagnosis

Diagnosing dehydration includes taking a recent health history , especially checking for the presence of specific illnesses, vomiting, diarrhea, constipation, fever, or other noticeable symptoms such as less frequent urination or lack of thirst. The doctor will also want to know about chronic illnesses and current medications. A physical examination will reveal dry lips, mouth, and nasal passages. Laboratory tests are important indicators of dehydration; blood tests include complete blood count (CBC), blood chemistries such as electrolytes (i.e., sodium, potassium, chloride), blood urea nitrogen (BUN), and creatinine, among others. Examination of urine and measurement of a 24-hour urine sample may be done to determine if output is normal or decreased. Heart rate and blood pressure will be measured and an electrocardiogrammay be taken to see if heart rhythm is altered. In hospitalized patients with possible dehydration, fluid intake and output may be measured to determine if kidney function is impaired.

Treatment

Treatment of dehydration requires restoring fluid level and hydration either by drinking more fluids or, when dehydration is more severe, receiving intravenous fluids. Electrolytes sometimes need replacing as fluids are being replaced. Fluid replacement products that contain essential body chemicals and nutrients are available at pharmacies and some supermarkets; pharmacists can offer advice about the best ones to help correct or prevent dehydration and to restore electrolyte balance. Monitoring fluid intake and urine output may be recommended by the doctor. Hospitalization is often necessary in severe dehydration that involves changes in blood pressure, heart rate, and nervous system or kidney function. Hospital care will include immediate replacement of fluids but may also involve treating an underlying chronic illness such as diabetes, kidney disease, or heart disease, which has resulted in fluid loss and dehydration. Treatment may also involve changing medications that have caused excess fluid loss.

Nutrition/Dietetic concerns

Besides drinking to restore fluid balance, normal consumption of food is necessary when someone is dehydrated. Because intestinal upsets with either diarrhea or vomiting can result in loss of interest in eating or the temporary inability to keep food down or digest it, foods should be kept simple and as soft or liquid as possible, including weak tea, broth, bouillon, plain soups, and lightly cooked vegetables. Large amounts of fluids should not be consumed all at once as this delays gastric emptying and encourages urination. It is recommended the dehydrated individuals sip fluids in small amounts at frequent intervals (e.g., 100–200 ml every 20 minutes) to achieve effective rehydration. High fiber foods such as whole fruit, bread, grains, and meat should be avoided until the intestinal tract has had a rest. Milk is not a clear liquid and may not be tolerated; milk is not ideal for fluid replacement. Caffeine—containing drinks and alcohol encourage excess urination and should be avoided.

The World Health Organization (WHO) recommends a homemade solution to help the dehydrated person correct fluid levels and also receive needed sugars and nourishment. To rehydrate the body, the following ingredients can be combined and sipped frequently over several hours:

  • 1 quart of water
  • three-fourths teaspoon of table salt
  • 1 teaspoon of baking powder
  • 4 tablespoons of sugar
  • 1 cup of orange juice

QUESTIONS TO ASK YOUR DOCTOR

  • How did I become dehydrated?
  • How can I drink more fluids without feeling bloated or going to the bathroom too often?
  • Besides drinking, what can I do to avoid becoming dehydrated again?
  • How will I know if I become dehydrated?

Prognosis

Dehydration can usually be reversed by correcting fluid levels through drinking or receiving fluids intravenously. Imbalances in the electrolyte sodium can cause too much water to be absorbed by brain cells, causing them to swell and rupture, a serious complication of dehydration. Underlying chronic diseases can complicate the correction of dehydration, resulting in organ system dysfunction. Severe dehydration can lead to shock and kidney failure, which can be life-threatening.

Prevention

Preventing dehydration is easier than treating it once it occurs. Drinking at least eight glasses of water a day prevents dehydration. More may be needed in hot weather. Beginning each day with a glass of water containing a small amount of lemon or other citrus juice helps restore fluid and blood sugar (glucose) levels that have diminished overnight. Water and other clear liquids (tea, juices, and clear soups) can be consumed slowly throughout the day rather than drinking too much at mealtimes, which will dilute digestive juices. Alcoholic beverages and excessive amounts of caffeine-containing drinks, which dehydrate the body, should be avoided.

Caregiver concerns

Any older individual who has an illness that causes fever, diarrhea, or vomiting may become dehydrated if fluid is not replaced through drinking water and other clear fluids. In these situations, caretakers must always watch for early signs of dehydration such as dry mouth , dark urine, and fatigue or irritability. Older individuals may not drink enough for various reasons: They may not feel thirsty it may be difficult to hold a glass containing liquid, or they have difficulty getting up from a chair or bed and want to avoid trips to the bathroom. Some elderly people take diuretic medications and have a time during the day, usually morning, when they urinate frequently. Some will not drink because they are incontinent and want to reduce the possibility of having accidents. Caregivers must always encourage drinking to replace what is excreted or replace fluid loss during certain illnesses through diarrhea, vomiting, or fever. Caregivers should also understand the symptoms of severe dehydration and know when to call the doctor or an ambulance.

KEY TERMS

Diuretic —A drug designed to encourage excretion of urine in people who accumulate excess fluid such as individuals with high blood pressure or heart conditions.

Electrolytes —Substances in the body that are able to conduct electricity. Electrolytes are essential in the normal functioning of body cells and organs.

Hydration —Taking in water or fluid to replace loss of fluid.

Incontinence —Loss of ability to control urination or to control bowel movements (fecal incontinence).

Postural hypotension (orthostatic hypotension) —A sudden drop in blood pressure when rising from a sitting or lying down position.

Rupture —A tear or break in body tissue of an organ.

Water homeostasis —A condition of adequate fluid level in the body in which fluid loss and fluid intake are equally matched and sodium levels are within normal range.

Resources

BOOKS

“Dehydration.” The Merck Manual of Diagnosis and Therapy, Section 6, edited by R. S. Porter. White House Station, NJ: Merck Research Laboratories, 2007.

OTHER

“Dehydration.” MayoClinic.com. January 3, 2007 [cited March 21, 2008]. http://www.mayoclinic.com/health/dehydration/DS00561.

Stöppler M. C., and William C. Shiel Jr. “Dehydration: How to recognize and Prevent its Effects.” Dehydration Symptoms, Causes, Prevention, Signs, and Effects. MedicineNet. January 4, 2006 [cited March 21, 2008]. http://www.medicinenet.com/script/main/art.asp?articlekey=16387&pf=3&page=1.

“Symptoms of Dehydration.” Heart Spring. February 14, 2007 [cited March 21, 2008]. http://www.heartspring.net/symptoms_of_dehydration.html.

ORGANIZATIONS

American Academy of Family Physicians, 114 Tomahawk Creek Parkway, Leawood, KS, 66211-2672, (800) 274 2237, (913) 906-6269, [email protected], www.familydoctor.org.

L. Lee Culvert

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Dehydration

Dehydration

Definition

Dehydration is the excessive loss of water from body tissues accompanied by an imbalance in essential electrolytes, such as sodium, potassium, and chloride.

Description

Dehydration occurs when the body loses more fluid than it takes in. Dehydration can be caused by illness, injury, infection , prolonged exposure to sun or high temperatures, inadequate water intake, or overuse of diuretics or other medications that increase urination.

Water is distributed throughout three compartments in the body: inside the cells (intracellular), in the tissue (interstitial), and in the bloodstream (intravascular). Each compartment contains differing amounts of electrolytes that must remain in balance in order for body organs and systems to function correctly. Dehydration upsets this delicate balance. Total body water also varies in relation to age, gender, and amount of body fat. Adult males have approximately 60% water content, adult females have 50%, infants have an estimated 77%, and the elderly have 46% to 52%. An increase in body fat causes a decrease in the percent fluid content because fat does not contain significant amounts of water.

Causes and symptoms

Different types of dehydration have different causes. When managing patients with dehydration, the type of water loss must be determined to ensure appropriate treatment. In addition, water and sodium levels in the body are closely related; if one is abnormal, the other often is too.

Isotonic dehydration is an equal loss of water and sodium. Isotonic means that the number of particles contained on one side of a permeable membrane is the same as on the other side, thus there is no fluid shift in either direction. The amount of intracellular and extracellular water remains in balance. This can be caused by a complete fast, vomiting, and diarrhea .

Hypertonic dehydration occurs when water loss is greater than sodium loss. Blood sodium levels may be >145 mmol/l (normal range=135 to 145 mmol/l). Higher blood sodium levels combined with decreased water in the intravascular space increases the osmotic pressure in the bloodstream, which, in turn, pulls more fluid out of the cells. This type of dehydration is usually caused by extended fever with limited oral rehydration. Mortality is more likely to occur from hypertonic than from isotonic dehydration.

Hypotonic dehydration occurs when sodium loss is greater than water loss. Blood sodium levels may be less than 135 mmol/l; and the osmotic pressure is greater inside the cells, which pulls more fluid out of the intravascular space into the intracellular space. This type of dehydration occurs with overuse of diuretics, which causes excessive sodium and potassium loss. Potassium depletion affects respiration, increases nausea, and, if severe enough, may cause respiratory arrest or central nervous system (CNS) seizures. Potassium depletion may also cause arrhythmias (an alteration in the heartbeat). As a result, patients are told to take diuretics with orange juice or to eat a banana, both of which are high in potassium.

Strenuous activity, excessive sweating, prolonged time in the sun, and extended vomiting or diarrhea cause fluid loss. Elderly people who move to warm, dry climates frequently become dehydrated because of the climate change combined with a tendency to not drink enough water. Large amounts of fluid can also be lost from prolonged fever. Healthy people require about 1 milliliter of water for each calorie their body metabolizes; but during a fever the metabolic rate increases by seven percent for each 1°F rise in body temperature. Fever also increases the respiratory rate, resulting in additional water loss from the lungs . Further causes of fluid loss that may be overlooked include caffeine and alcohol consumption, which increase urination and fluid excretion.

Decreased oral intake of fluids is a common cause of dehydration and often occurs during times of appetite loss from illness or after oral surgery or injury. The elderly are at high risk for decreased intake because their thirst mechanism may no longer function or they may be physically unable to get a drink. Infants, another high-risk group, are more likely to develop dehydration than adults because they have a higher metabolic rate and their immature kidneys have difficulty concentrating urine. Children who do not wet their diapers for three hours or more are dehydrated. Dehydration is also associated with disorders of the adrenal glands , which regulate water-electrolyte balance; diabetes mellitus ; eating disorders; renal disease; and chronic lung disease.

Symptoms of dehydration at any age may include some or all of the following: cracked lips, dry or sticky mucous membranes, sunken eyes, lethargy, and/or confusion. Urine output is minimal and the skin loses its elasticity (turgor) and is slow to return to its normal position after being raised off the back of the hand (tenting). The heart rate and respiratory rate may be elevated. A dehydrated infant may not shed tears when crying and may have a depressed fontanel (soft spot on their head), although recent studies have shown that a depressed fontanel is not an accurate indicator of dehydration.

Diagnosis

The general diagnosis of dehydration can be made based on the patient's symptoms and medical history. Physical examination may reveal any of the symptoms mentioned above, along with shock , rapid heart rate, and low blood pressure . Blood tests are required to determine what deficiency exists (or what is elevated) so that therapy for electrolyte replacement can be planned. Blood tests to check electrolyte levels and urine tests such as urine specific gravity are used to evaluate the severity of the fluid loss. Other laboratory tests may be ordered to determine if an underlying condition (e.g., diabetes or an adrenal gland disorder) is the cause.

Treatment

Increased fluid intake and replacement of lost electrolytes are usually sufficient to restore fluid balance in patients who are mildly or moderately dehydrated. For individuals who are mildly dehydrated, just drinking plain water may be all the treatment that is needed. Adults may replace lost electrolytes by drinking sports beverages, such as Gatorade or Recharge. Parents should follow label instructions when giving children Pedialyte or other commercial products recommended for the treatment of dehydration in children. Children who are dehydrated should be given only clear fluids for the first 24 hours.

A child who is vomiting should sip one or two teaspoons of liquid every 10 minutes. A child who is less than a year old and who is not vomiting should be given one tablespoon of liquid every 20 minutes. A child who is more than one year old and who is not vomiting should take two tablespoons of liquid every 30 minutes. A baby who is being breast-fed should be given clear liquids for two consecutive feedings before breastfeeding is resumed. A bottle-fed baby should be given formula diluted with water to half the formula strength for the first 24 hours after symptoms of dehydration are identified.

To calculate fluid loss accurately, weight changes should be charted every day and a record kept of how many times a patient vomits or has diarrhea. A record of fluid output (including sputum or vomit) and of fluid intake or replacement should be kept for at least 24 to 48 hours to see if balance is being accomplished. Parents should note how many times a baby's diaper must be changed. If dehydration continues, emergency department treatment or hospitalization to receive intravenous fluids and electrolytes may be necessary.

Children and adults can gradually return to their normal diet after they have stopped vomiting and no longer have diarrhea. Gelatin is often a welcomed substitute for additional water and does count as fluid replacement. Bland foods should be reintroduced first, with other foods added as the digestive system is able to tolerate them. Milk, ice cream, cheese, and butter should not be eaten until 72 hours after symptoms have disappeared.

When treating dehydration, the underlying cause must be addressed. For example, if dehydration is caused by vomiting or diarrhea, medications should be prescribed to resolve these symptoms. Patients who are dehydrated due to diabetes, kidney disease, or adrenal gland disorders must receive treatment for these conditions as well as for the resulting dehydration. If dehydration is being caused by diuretics. a dose adjustment made by the physician or a change to a different diuretic may be necessary.

Prognosis

Mild dehydration rarely results in complications. If the cause is eliminated and lost fluid is replaced, mild dehydration can usually be resolved in 24 to 48 hours. Vomiting and diarrhea that continue for several days without adequate fluid replacement can be fatal since more is lost than water and sodium. Severe potassium loss may lead to cardiac arrhythmias, respiratory distress or arrest, or convulsions (seizures). The risk of life-threatening complications is greater for young children and the elderly. However, dehydration that is rapidly recognized and treated has a good outcome.

Health care team roles

The nurse and the physician have the greatest responsibility in recognizing and treating dehydration. For hospitalized patients, the physician should order appropriate fluid and electrolyte replacement and the nurse should ensure that the correct fluids are given to the patient. The nurse should monitor the patient for signs that the dehydration (e.g., decrease in fever, increase in blood pressure, reduced heart rate) is resolving and should notify the physician if it is not.

Blood tests used to diagnose dehydration are collected by specially trained nursing assistants or by laboratory technicians. Outpatient samples in a physician's office may be taken by the nurse or a technician. In some institutions, the nurse collects the blood sample. Usually, urine samples are collected by the nurse, and results calculated by the laboratory technician.

Prevention

Patients who are vomiting or who have diarrhea can prevent dehydration by drinking enough fluid to keep their urine the color of pale straw. Infants and young children with diarrhea and vomiting can be given electrolyte solutions such as Pedialyte to help prevent dehydration, as well as suppository medication to stop the vomiting. People who are not ill can maintain proper fluid balance by drinking several glasses of water before going outside on a hot day. It is also a good idea to avoid coffee and tea, which increase body temperature and water loss.

Patients should ask a pharmacist whether or not any medications they are taking may cause dehydration and what to do to prevent it other than adequate fluid intake. Prompt medical attention should be sought to correct any underlying condition that increases the risk of dehydration.


KEY TERMS


Extracellular —Outside the cells.

Hypertonic —One solution having a greater amount of solute (dissolved substance in a solution) than another solution, thus it exerts more osmotic pressure than the second solution and the body will attempt to equalize pressure by passing fluid through the cell membranes.

Hypotonic —One solution having a lesser amount of solute than another solution, thus it exerts less osmotic pressure than the second solution.

Intracellular —Inside the cells.

Isotonic —Two solutions exerting the same amount of osmotic pressure on a cell membrane.

Osmotic pressure —The pressure exerted on a semipermeable membrane that separates two solutions and the particles they contain.


Resources

BOOKS

Andreoli, Thomas E., et al., eds. Cecil Essentials of Medicine, 5th ed. Philadelphia, PA: W.B. Saunders Company, 2001.

Porth, C. Pathophysiology: Concepts of Altered Health States. Philadelphia, PA: Lippincott, 1998.

Rakel, Robert E., ed. Conn's Current Therapy 2000. Philadelphia, PA: W.B. Saunders Company, 1999.

Thelan, Lynne, et al. Critical Care Nursing: Diagnosis and Management. St. Louis, MO: Mosby, 1998.

PERIODICALS

Pace, B. "Preventing Dehydration from Diarrhea." JAMA 285, no. 3 (2001): 362.

Sullivan, A. "Hydration for Adults." Nursing Standard 14, no. 8 (1999): 44-46.

Abby Wojahn, R.N.,B.S.N.,C.C.R.N.

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