Under conditions of high heat and activity, up to 60% of the cardiac output may pass through the skin for cooling and sweat production. Loss of fluid occurs by sweating. To prevent dehydration in hot environments, workers should drink at least an extra cupful of water every hour, an extra 1.5 to 2 L a day (Table 33.2). Because rapid weight loss in the heat means water loss and not fat loss, people losing weight should drink more water, possibly even 10 L, to maintain body weight. The urine should be plentiful and light colored. Urine that is dark, strong smelling, or of reduced volume indicates a large fluid deficit (3).
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