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Prevent water intoxication: How to thwart a stealthy summertime killer


June 2007

An hour ago, you drained your fifth liter of water, trying to beat the triple-digit heat of a rim-to-rim Grand Canyon hike. Now you’re feeling dizzy. Time to slam another Nalgene? Hold off. Instead of heat exhaustion, you could be suffering from hyponatremia, a condition brought on by drinking too much water.

When your body retains excessive fluid, the concentration of electrolytes (such as sodium) in your cells and blood go out of balance, causing the cells to expand. Most cells can handle the swelling, but brain cells cannot; the skull prevents them from enlarging, leading to complications such as dizziness and cerebral edema. If victims keep drinking and symptoms go untreated, they can slip into a coma and die.

Hyponatremia is rare compared to other heat-related illnesses; Grand Canyon National Park reports 5 to 10 cases in a typical summer. However, diagnosis can be tricky because early hyponatremia looks a lot like dehydration – which requires the opposite treatment.

Avoid It
• Give yourself several days to acclimatize to a hot environment.
• Drink small amounts at each break, guided by your thirst level.
• Keep track of your fluid intake; in high heat, hikers should drink half a liter of water per hour.
• Salty snacks and sports drinks enhanced with electrolytes can keep sodium levels in balance.

Detect It
• Initial hyponatremia symptoms mimic those of heat exhaustion: nausea, vomiting, and dizziness.
• The above clues, plus excessive hydration, sloshing in the belly, lack of thirst, clear urine, confusion, and seizures are signs of hyponatremia.
• Symptoms can appear hours after the hike’s end, when cells have absorbed all the excess water.

Treat It
• Determine if the victim has been drinking too much. If so, stop all water consumption and allow him or her to rest and urinate.
• If their condition worsens, provide oral hydration salts or bouillon cubes (4 tablets or cubes in 4 ounces of water) to draw water from the cells.
• Snacks such as peanuts, granola bars, and potato chips can also restore salts.

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