Most of your body is made up of water, with up to 75% of your body's weight due to H2O. Most of the water is found within the cells of your body (intracellular space). The rest is found in the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).
Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water levels in the body. We lose water routinely when we:
- breathe and humidified air leaves the body;
- sweat to cool the body; and
- urinate or have a bowel movement to rid the body of waste products.
In a normal day, a person has to drink a significant amount of water to replace this routine loss.
Diarrhea is the most common reason a person loses excess water. Diarrhea consists of unusually frequent or unusually liquid bowel movements and excessive watery evacuations of fecal material. Persistent diarrhea is both uncomfortable and dangerous, as a significant amount of water can be lost with each bowel movement. Worldwide, more than four million children die each year because of dehydration from diarrhea.
Vomiting is the act of forcible emptying of the stomach, in which the stomach has to overcome the pressures that are normally in place to keep food and secretions within the stomach. The stomach almost turns itself inside out - forcing itself into the lower portion of the esophagus (the tube that connects the mouth to the stomach) during a vomiting episode. Constant vomiting can be a serious cause of fluid loss and it is difficult for a person to replace water if they are unable to tolerate liquids.
Your body can lose significant amounts of water when it tries to cool itself by sweating. Whether the body is hot because of the environment (for example, working in a warm environment), intense exercising in a hot environment, or because a fever is present due to an infection; the body uses a significant amount of water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk will generate up to 16 ounces of sweat (one pound of water).
In people with diabetes, elevated blood sugar levels cause sugar to spill into the urine, and water then follows, which can cause significant dehydration. For this reason, frequent urination and excessive thirst are among the symptoms of diabetes.
The skin has an important role to play in the fluid and temperature regulation of the body. If enough skin area is injured, the ability to maintain that control can be lost. Burn victims become dehydrated because water seeps into the damaged skin. Other inflammatory diseases of the skin are also associated with fluid loss.
The inability to drink adequately is another potential cause of dehydration. Whether it is the lack of availability of water or the lack of strength to drink adequate amounts, this, coupled with routine or excessive amounts of water loss, can compound the degree of dehydration.
The body's initial responses to dehydration are thirst to increase water intake along with decreased urine output to try to conserve water. The urine will become concentrated and more yellow in color. As the level of water loss increases, more symptoms can become apparent, such as increased thirst, dry mouth, cessation of tear production by the eyes, cessation of sweating, muscle cramps, nausea and vomiting, heart palpitations, and lightheadedness (especially when standing). With severe dehydration, confusion and weakness will occur as the brain and other body organs receive less blood. Finally, coma and organ failure will occur if the dehydration remains untreated and can cause death.
Dehydration is often a clinical diagnosis. Aside from diagnosing the reason for dehydration, the health care professional's examination of the patient will assess the level of dehydration. Initial evaluations may include:
- Mental status tests to evaluate whether the patient is awake, alert, and oriented.
- Vital sign assessments may include postural readings (blood pressure and pulse rate are taken lying down and standing). With dehydration, the pulse rate may increase and the blood pressure may drop because the intravascular space is depleted of water.
- Temperature may be measured to assess fever.
- Skin will be checked to see if sweat is present and to assess the degree of elasticity. As dehydration progresses, the skin loses its water content and becomes less elastic.
- Infant evaluation: infants may have additional evaluations performed, including checking for a soft spot on the skull (sunken fontanelle), assessing the suck mechanism, muscle tone, or loss of sweat in the armpits and groin.
- Pediatric patients are often weighed during routine visits; thus a body weight measurement may be helpful in assessing how much water has been lost with the acute illness.
In some cases, blood tests to measure potential electrolyte abnormalities and urinalysis may be ordered to determine the level of dehydration in the patient.
Fluid replacement is the treatment for dehydration. This may be attempted by replacing fluid by mouth, but if this fails, intravenous fluid (IV) may be required. Should oral rehydration be attempted, frequent small amounts of clear fluids should be used.
Clear fluids include:
- clear broths,
- Jell-O, and
- other replacement fluids that may contain electrolytes (for example, Pedialyte, Gatorade, Powerade)
Dehydration occurs over time. If it can be recognized in its earliest stages, and if its cause can be addressed, then home treatment may be adequate. Steps a person can take at home to prevent severe dehydration include:
- People with vomiting and diarrhea can try to alter their diet and use medications to control symptoms to minimize water loss.
- Acetaminophen or ibuprofen may be used to control fever. Ibuprofen may irritate the stomach and cause nausea and vomiting, so it should be used with caution in individuals who already have these symptoms.
- Fluid replacements may be attempted by replacing fluid by mouth with frequent small amounts of clear fluids.
If the individual becomes confused or lethargic; if there is persistent, uncontrolled fever, vomiting, or diarrhea; or if there are any other specific concerns, then medical care should be accessed. EMS or 911 should be activated for any person with altered mental status or is unable to rehydrate orally.
Complications of dehydration may occur because of the dehydration, and/or because of the underlying disease or situation that causes the fluid loss. Complications that may occur include:
- kidney failure,
- heat-related illnesses (heat exhaustion or heat stroke), and
- electrolyte abnormalities.
Plan ahead and bring extra water to all outdoor events where increased sweating, activity, and heat stress will increase fluid loss. Encourage athletes and people who work outside to replace fluids at a rate that equals the loss.
Check weather forecasts for high heat index days. When temperatures are high, avoid exercise, outdoor exposure, and plan events that must occur outside during times of the day when temperatures are lower.
The young and elderly are most at risk of dehydration. Ensure that older people, infants, and children have adequate drinking water or fluids available and assist them as necessary. Encourage people who are incapacitated or impaired to drink plenty of water and assure they are provided with adequate fluids. During heat waves, attempts should be made to check on the elderly in their homes. During the Chicago heat wave of 1995, more than 600 people died in their homes from heat exposure.
Avoid alcohol consumption, especially when it is very hot, because alcohol increases water loss and impairs your ability to recognize early signs associated with dehydration.
Wear light-colored and loose-fitting clothing if you must be outdoors when it is hot outside. Drink plenty of water and carry a personal fan or sit in an area where a fine water sprayer (mister) is used to cool yourself.
Break up your exposure to hot temperatures. Find air-conditioned or shady areas and allow yourself to cool between exposures. Taking someone into a cooled area for even a couple of hours each day will help prevent the cumulative effects of high heat exposure.
Know the signs and symptoms of heat cramps, heat rash, heat exhaustion, and heat stroke. Preventing dehydration is one step to avoid these conditions.
- The body needs water to function.
- Dehydration occurs when water intake is less than water loss.
- Symptoms range from mild to life-threatening.
- Prevention is the important first step in treating dehydration.
- The young and the elderly are especially susceptible to dehydration.
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- Medscape: "Dehydration." Dec. 7, 2018.
- Medscape: "Dehydration Treatment and Management." Dec. 7, 2018.
- NOAA: "Climate History: July 1995 Chicago-Area Heat Wave."