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

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