Know what causes dehydration so you can avoid it

By Allen Douma, M.D.
Tribune Media Services

Q. Would you please write something about flu dehydration?

A. Dehydration occurs when the body’s output of water exceeds its intake. So dehydration is the result of either insufficient intake or excessive loss.

Loss occurs through urine, evaporation through the skin (sweat) and the lungs, and loss through the digestive tract (diarrhea, vomiting or both).

Dehydration can increase thirst and cause a sense of light-headedness or feeling faint. People with mild or even moderate dehydration may have no symptoms except thirst. A frequent indication of dehydration is darkening of the urine. As less fluid is excreted, the chemicals in the urine impart a deepening yellow to orange color.

Medical conditions are frequent causes of dehydration. The three most common are diarrhea, increased water loss because of an elevated body temperature, and decreased water intake.

Because of high temperatures, people with influenza evaporate more water from their body, both through the skin and the lungs. And, because the person is feeling so bad, they often do not get enough liquids either by drinking or eating.

It typically takes days for dehydration to occur from medical problems. However, someone with severe diarrhea, especially a young child, can become dehydrated within a few hours.

Heat disorders are most likely to occur when certain risk factors are present, which include: decreased sweat production (dehydration, obesity, general skin disease, etc.), lowered evaporation of sweat (poorly ventilated clothes), increased dehydration (due to reduced fluid intake, alcohol, etc.), and/or diminished blood flow to the skin (low blood pressure, reduced output of the heart, etc.). Some drugs can adversely affect these functions as well.

Risk of heat-related problems increases with age, concurrent illness, reduced physical activity, and insufficient acclimatization to increased temperature.

The four specific medical disorders because of heat exposure are heat syncope, heat cramps, heat exhaustion and heat stroke.

Heat syncope, or sudden fainting, can result when the body senses insufficient blood flow to the skin to cool the body. It responds by dilating all blood vessels, which results in a rapid drop in blood pressure and subsequent fainting. Typically, vigorous physical activity precedes such an episode.

Heat cramps are slow, painful skeletal muscle contractions that result from the depletion of salts (electrolytes) when the loss of sweat is replaced by water alone. Here, too, physical activity usually precedes the onset of symptoms.

Heat exhaustion usually results from a combination of heavy physical activity, inadequate salt intake and a hot environment. Symptoms of heat syncope and heat cramps may be present, along with increased body temperature and changes in the blood vessels and nervous system.

Heat stroke is the most serious of the heat-related health disorders and is a life-threatening medical emergency. Heat stroke is characterized by rapid onset, sometimes without warning, of signs of brain dysfunction like impaired consciousness, high fever and absence of sweating.

To help decrease your risk, drink plenty of fluids, replace salts and minerals, wear appropriate clothing, pace yourself, stay cool indoors, and adjust to the environment.

UPDATE ON ALLERGENS: It almost seems like a horror movie to read the results of research sponsored by the National Institutes of Health on asthma and allergens in homes. The researchers found that home invaders were causing disease by leaving saliva, fecal material, secretions, cast skins, and dead bodies behind. And all of these cause allergic responses and asthma, especially in children.

They also found that these invaders, cockroaches, worsen asthma symptoms more than either dust mites or pet allergens.

Fortunately, they also found that general cleaning practices, proven extermination techniques, and consistent maintenance methods can bring the allergen levels under control.