Dehydration

From Wikipedia, the free encyclopedia

Dehydration (hypohydration) is defined as excessive loss of body water.^[1] It is literally the removal of water (Ancient Greek: ὕδωρ, hýdōr) from an object. In physiological terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes. Some definitions even require a rise in blood sodium concentration^[2], but in reality a loss of body water usually accompanies a loss of solutes as well.^[2]

[edit] Difference from hypovolemia

Hypovolemia is specifically a decrease in volume of blood plasma.^[3][4]. Furthermore, hypovolemia defines water deficiency only in terms of volume rather than specifically water.

Nevertheless, the conditions are usually appear simultaneously.

[edit] Medical causes of dehydration in humans

In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These include:

• External or stress-related causes
  • Prolonged physical activity with sweating without consuming adequate water, especially in a hot and/or humid environment
  • Prolonged exposure to dry air, e.g. in high-flying airplanes (5-12% relative humidity)
  • Blood loss or hypotension due to physical trauma
  • Diarrhea
  • Hyperthermia
  • Shock (hypovolemic)
  • Vomiting
  • Burns
  • Lacrimation
  • Use of Methamphetamine, Amphetamine and other stimulants.
  • Drinking of Alcohol. (In place of water)

• Infectious diseases
  • Cholera
  • Gastroenteritis
  • Shigellosis
  • Yellow fever

• Malnutrition
  • Electrolyte disturbance
    • Hypernatremia (also caused by dehydration)
    • Hyponatremia, especially from restricted salt diets
  • Fasting
  • Recent rapid weight loss may reflect progressive depletion of fluid volume (the loss of 1 L of fluid results in a weight loss of 1 kg or 2.2 lb).^[5]
  • Patient refusal of nutrition and hydration
  • Inability to swallow (obstruction of the esophagus)

• Other causes of obligate water loss
  • Severe hyperglycemia, especially in Diabetes mellitus
    • Glycosuria

[edit] Symptoms and prognosis

Symptoms may include headaches similar to what is experienced during a hangover, muscle cramps, a sudden episode of visual snow, decreased blood pressure (hypotension), and dizziness or fainting when standing up due to orthostatic hypotension. Untreated dehydration generally results in delirium, unconsciousness, swelling of the tongue and in extreme cases death.

Dehydration symptoms generally become noticeable after 2% of one's normal water volume has been lost. Initially, one experiences thirst and discomfort, possibly along with loss of appetite and dry skin. This can be followed by constipation. Athletes may suffer a loss of performance of up to 30%^[6], and experience flushing, low endurance, rapid heart rates, elevated body temperatures, and rapid onset of fatigue.

Symptoms of mild dehydration include thirst, decreased urine volume, abnormally dark urine, unexplained tiredness, irritability, lack of tears when crying, headache, dry mouth, dizziness when standing due to orthostatic hypotension, and in some cases can cause insomnia.

In moderate to severe dehydration, there may be no urine output at all. Other symptoms in these states include lethargy or extreme sleepiness, seizures, sunken fontanel (soft spot) in infants, fainting, and sunken eyes.

The symptoms become increasingly severe with greater water loss. One's heart and respiration rates begin to increase to compensate for decreased plasma volume and blood pressure, while body temperature may rise because of decreased sweating. Around 5% to 6% water loss, one may become groggy or sleepy, experience headaches or nausea, and may feel tingling in one's limbs (paresthesia). With 10% to 15% fluid loss, muscles may become spastic, skin may shrivel and wrinkle (decreased skin turgor), vision may dim, urination will be greatly reduced and may become painful, and delirium may begin. Losses greater than 15% are usually fatal. ^[7]

In people over age 50, the body’s thirst sensation diminishes and continues diminishing with age. Many senior citizens suffer symptoms of dehydration. Dehydration along with hyperthermia results in seniors dying during extreme hot weather.

Dehydration is the excessive loss of water from the body. Diseases of the gastrointestinal tract can lead to dehydration in various ways. Often, dehydration becomes the major problem in an otherwise self-limited illness. Fluid loss may even be severe enough to become life-threatening.

Numerous studies have shown that for terminally ill patients who choose to die, deaths by dehydration are generally peaceful, and not associated with suffering, when supplemented with adequate pain medication.^{[8][9][10][11][12][13]}

[edit] Treatment

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Nurses encourage a patient to drink an Oral Rehydration Solution to improve dehydration he acquired from cholera.

The best treatment for minor dehydration is drinking water and stopping fluid loss. Sports drinks and other rehydration fluids are preferable to water; plain water restores only the volume of the blood plasma, inhibiting the thirst mechanism before solute levels can be replenished.^[14] To stop fluid loss from vomiting and diarrhea, avoid solid foods and drink only clear liquids. In some cases, eating of salted foods may have a positive impact on the person. However, eating salted foods should come with more intake of a clear liquid. It is wise to slowly drink liquids when dehydrated. ^[15]

In more severe cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (rehydration, through oral rehydration therapy or intravenous therapy). Even in the case of serious lack of fresh water (e.g., at sea or in a desert), drinking seawater or urine does not help, nor does the consumption of alcohol. It is often thought that the sudden influx of salt into the body from seawater will cause the cells to dehydrate and the kidneys to overload and shut down but it has been calculated that an average adult can drink up to 0.1 liters of seawater per day before the kidneys start to fail^{[citation needed]}

When dehydrated, unnecessary sweating should be avoided, as it wastes water. If there is only dry food, it is better not to eat, as water is necessary for digestion. For severe cases of dehydration where fainting, unconsciousness, or other severely inhibiting symptom is present (the patient is incapable of standing or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is the norm in all but the most extreme cases.

[edit] Avoiding dehydration

Dehydration is best avoided by drinking plenty of water. The greater the amount of water lost through perspiration, the more water must be consumed to replace it and avoid dehydration. Since the body cannot tolerate large deficits or excesses in total body water, consumption of water must be roughly concurrent with the loss (in other words, if one is perspiring, one should also be drinking water frequently). Drinking water beyond the needs of the body entails little risk when done in moderation, since the kidneys will efficiently remove any excess water through the urine with a large margin of safety.

A person's body, during an average day in a temperate climate such as the United Kingdom, loses approximately 2.5 litres of water.^{[citation needed]} This can be through the lungs as water vapor, through the skin as sweat, or through the kidneys as urine. Some water (a less significant amount, in the absence of diarrhea) is also lost through the bowels. In warm or humid weather or during heavy exertion, however, the water loss can increase by an order of magnitude or more through perspiration; all of which must be promptly replaced. In extreme cases, the losses may be great enough to exceed the body's ability to absorb water from the gastrointestinal tract; in these cases, it is not possible to drink enough water to stay hydrated, and the only way to avoid dehydration is to reduce perspiration (through rest, a move to a cooler environment, etc.)

A useful rule of thumb for avoiding dehydration in hot or humid environments or during strenuous activity involves monitoring the frequency and character of urination. If one develops a full bladder at least every 3-5 hours and the urine is only lightly colored or colorless, chances are that dehydration is not occurring; if urine is deeply colored, or urination occurs only after many hours or not at all, water intake may not be adequate to maintain proper hydration.

When large amounts of water are being lost through perspiration and concurrently replaced by drinking, maintaining proper electrolyte balance becomes an issue. Drinking fluids that are hypertonic or hypotonic with respect to perspiration may have grave consequences (hyponatremia or hypernatremia, principally) as the total volume of water turnover increases.

If water is being lost through abnormal mechanisms such as vomiting or diarrhea, an imbalance can develop very quickly into a medical emergency.

During sports events such as marathons, water stops and water breaks are provided to avoid dehydration of athletes.

[edit] See also

• Hypovolemia, a depletion of blood volume that can be caused by dehydration
• Safe water
• Starvation
• Water intoxication
• Water therapy
• Water deprivation test

[edit] References

• Ira R. Byock, M.D., Patient Refusal of Nutrition and Hydration: Walking the Ever-Finer Line. American Journal Hospice & Palliative Care, pp. 8-13. (March/April 1995)

[edit] Notes

1. ^ MedicineNet > Definition of Dehydration Retrieved on July 2, 2009
2. ^ ^{a b} TheFreeDictionary.com --> dehydration Citing The American Heritage Science Dictionary 2005. Retrieved on July 2, 2009
3. ^ MedicineNet > Definition of Hypovolemia Retrieved on July 2, 2009
4. ^ TheFreeDictionary.com --> hypovolemia Citing Saunders Comprehensive Veterinary Dictionary, 3 ed. Retrieved on July 2, 2009
5. ^ Dehydration Symptoms - Benefits of Drinking Water - Signs of Fluid Imbalance
6. ^ Bean, Anita (2006). The Complete Guide to Sports Nutrition. A & C Black Publishers Ltd.. pp. 81–83. ISBN 0713675586. 
7. ^ http://faculty.washington.edu/kepeter/118/notes/pdf-set5/118water-bal-06.htm
8. ^ Ganzini L, Goy E, Miller L, Harvath T, Jackson A, Delorit M (2003). "Nurses' experiences with hospice patients who refuse food and fluids to hasten death". N Engl J Med 349 (4): 359–65. doi:10.1056/NEJMsa035086. PMID 12878744. 
9. ^ McAulay D. "Dehydration in the terminally ill patient". Nurs Stand 16 (4): 33–7. PMID 11977821. 
10. ^ Van der Riet P, Brooks D, Ashby M (2006). "Nutrition and hydration at the end of life: pilot study of a palliative care experience". J Law Med 14 (2): 182–98. PMID 17153524. 
11. ^ Miller F, Meier D (1998). "Voluntary death: a comparison of terminal dehydration and physician-assisted suicide". Ann Intern Med 128 (7): 559–62. PMID 9518401. 
12. ^ Printz L (1992). "Terminal dehydration, a compassionate treatment". Arch Intern Med 152 (4): 697–700. doi:10.1001/archinte.152.4.697. PMID 1373053. 
13. ^ Sullivan R (1993). "Accepting death without artificial nutrition or hydration". J Gen Intern Med 8 (4): 220–4. doi:10.1007/BF02599271. PMID 8515334. 
14. ^ "Formulating carbohydrate-electrolyte drinks for optimal efficacy." Murray, R. & Stofan, J. (2001).
15. ^ "Healthwise Handbook," Healthwise, Inc. 1999

[edit] External links

Look up dehydration in Wiktionary, the free dictionary.

• Water requirements in adults
• Definition of dehydration by the U.S. National Institutes of Health's MedlinePlus medical encyclopedia
• Rehydration Project at rehydrate.org