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Title: The Wonderful World of Water Reading Passage Dehydration is the lack of adequate body fluids for the body to carry on normal functions at an optimal level (by loss, inadequate intake, or a combination of both). Losses of only a few percent in an adult and up to 5% in infants are considered mild dehydration. Dehydration can be caused by excessive loss of water from the body as in vomiting, diarrhea, excessive urine output, and excessive sweating. It can also occur from inadequate intake as in nausea, pharyngitis, and acute illness with loss of appetite. To prevent dehydration, experts recommend that everyone drink six to eight glasses of water a day. Divers need to take into consideration additional concerns for fluid loss and replacement. Scuba tanks, for instance, have extremely dry air inside. As this air is taken into the lungs and saturated, nearly twice the normal amount of water is lost from the body. Negative pressure breathing also causes divers to lose about 350cc/hour from their circulating blood bolume, a phenomenon called immersion diuresis and seen also in snorkelers and swimmers. Cold temperature also inhibits anti-diuretic hormone(ADH), causing peripheral vasoconstriction and stimulating diuresis (urinating) resulting in losses of plasma volume. Ther hypercarbia (increased CO2) associated with diving decreases anti-diuretic hormone, promoting fluid loss from the plasma volume. These indicate the importance of entering a dive well-hydrated. Pre-hydration of divers should include regular ingestion of fluids several hour before, 15-20 minutes before and between dives, particularly if multiple dives are to be made each day. Signals of dehydration in the body include heartburn, chronic pain, low back pain, headache, mental irritation and depression, and water retention. Physical examination also shows signs of low blood pressure, rapid heart rate, and shock. Oral re-hydration may be sufficient for mild dehydration. Intravenous fluids and hospitalization may be necessary for moderate to sever dehydration. Rapid recognition and treatment for dehydration results in a good outcome. |
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