Dehydration is the removal of water (hydor in ancient Greek) from an object. Medically, dehydration is a serious and potentially life-threatening condition in which the body contains an insufficient volume of water for normal functioning.

The term "volume depletion" is similar to dehydration, but it refers to the loss of salts as well as water. Also see Hypovolemia.

Medical causes of dehydration

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
  • Blood loss or hypotension due to physical trauma
  • Diarrhea
  • Hyperthermia
  • Shock
  • Prolonged physical activity without consuming adequate water, especially in a hot environment
  • Survival situations, especially desert survival conditions
  • Vomiting

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

• Malnutrition
  • Electrolyte imbalance
    • Hypernatremia (also caused by dehydration)
    • Hyponatremia, especially from restricted salt diets
  • excessive consumption of alcohol
  • Fasting
  • Patient refusal of nutrition and hydration

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

Symptoms and prognosis

Symptoms may include headaches similar to what is experienced as a hangover, 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, and 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. Athletes may suffer a loss of performance of up to 50%, and experience flushing, low endurance, rapid heart rates, elevated body temperatures, and rapid onset of fatigue.

The symptoms become increasingly severe with greater water loss. One's heart and respiration rates will increase to compensate for decreased plasma volume and blood pressure, while body temperature may rise due to 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, vision may dim, urination will be greatly reduced and may become painful, and delirium may begin. Losses of greater than 15% are usually fatal. [1]

Treatment

Correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (rehydration). 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.

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. The best treatment for minor dehydration is consumption of an electrolyte-balanced fluid like a sports drink. For severe cases of dehydration where fainting, unconsciousness, or any other severely inhibiting symptom is present (the patient is incapable of standing or thinking clearly), emergency attention is required. Fluids will be given through an IV, and within a few hours, the patient will return to normal unless a complication occurred.

Avoiding dehydration

A person's body loses, during an average day in a temperate climate such as the United Kingdom, approximately 2.5 litres of water. This can be through the lungs as water vapor, through the skin as sweat, or through the kidneys as urine. Some (a less significant amount, in the absence of diarrhea) is also lost through the bowels.

During vigorous exercise or in a hot environment, it is easy to lose several times this amount. Heavy exercise in high temperatures could cause the loss of over 2.5 litres of fluid per hour, which exceeds the body's absorptive capacity.

Ethical concerns

Judge Lynch of the Massachusetts Supreme Judicial Court argued that death by dehydration symptoms was "cruel and violent" in his opinion on the 1986 Brophy case:

• The mouth would dry out and become caked or coated with thick material.
• The lips would become parched and cracked.
• The tongue would swell, and might crack.
• The eyes would recede back into their orbits and the cheeks would become hollow.
• The lining of the nose might crack and cause the nose to bleed.
• The skin would hang loose on the body and become dry and scaly.
• The urine would become highly concentrated, leading to burning of the bladder.
• The lining of the stomach would dry out and the sufferer would experience dry heaves and vomiting.
• The body temperature would become very high.
• The brain cells would dry out, causing convulsions.
• The respiratory tract would dry out, and the thick secretions that would result could plug the lungs and cause death.
• At some point within five days to three weeks, the major organs, including the lungs, heart, and brain, would give out and the patient would die.

Be advised the death due to dehydration can occur in 3 days (or less in hot weather) and no one normally lives more than about 5-6 days

External links

• National Center for Home Food Preservation - Food Dehydrators
• Tips from the SAS Survival Guide by John Wiseman
• Dehydration Information
• Report of a navy officer including some tips
• Water requirements in adults
• Definition of Dehydraton by the US National Institutes of Health

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)es:Deshidratación