Dehydration is the loss of water and salts that are essential for normal body function.
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.
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
- excessive heat
- excessive sweating
- 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
- 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.
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.
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 (2–4 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 (4–8 ounces). Food should not be restricted. Children with mild to moderate dehydration should be given 50 to 100 mL (roughly 2–3.5 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.
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.
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.
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).
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.
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Crystal Heather Kaczkowski, MSc. Maureen Haggerty