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Water and Electrolytes
Pages 247-261

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From page 247...
... The normal daily turnover of water via these routes is approximately 4% of total body weight in adults and much higher, 15% of total body weight, in infants. As Figure 11-1 shows, even in the absence of visible perspiration, approximately one-half of the turnover occurs through what is called insensible water loss, i.e., water lost from the lungs and skin.
From page 248...
... Diarrhea can increase intestinal loss dramatically. Figure 1 1-1 includes an estimate of minimal urine volume required when urinary solute concentration is maximal (about 1,400 mosmol/ liter in the healthy adult and 700 mosmol/liter in the infant)
From page 249...
... Median daily intake of water as such among respondents in the 1977-1978 Nationwide Food Consumption Survey was 2.8 cups (USDA, 19841. In 1981, daily per capita milk consumption was approximately one and one-third cups, per capita coffee and tea consumption was about one and onehalf cups, and soft drink consumption was one and three-fourths cups per capita.
From page 250...
... Since milk is X7% water and average milk secretion is 750 ml/day for the first 6 months, the extra fluid required would be less than 1,000 ml/day. Infants and Children Infants must be treated as a separate category for several reasons: their large surface area per unit of body weight, their higher percentage of body water and its high rate of turnover, the limited capacity of their kidneys for handling the solute load from high protein intakes required for growth, and their susceptibility to severe dehydration due in part to their inability to express thirst.
From page 251...
... When sodium intake is high, the aldosterone level decreases and urinary sodium increases. When dietary sodium intake is low, the aldosterone level increases and urinary excretion of sodium rapidly falls almost to zero.
From page 252...
... Because of the difficulty of assessing sodium use from dietary recall, dietary surveys probably underestimate total sodium intake, even when contributions of water and other marginal sources are included. From data on daily urinary sodium excretion over 24 hours, Dahl and Love (1957)
From page 253...
... or less (NRC, 19891. Pregnancy and Lactation During pregnancy, there is an increased need for sodium because of the increased extracellular fluid volume in the mother, the requirements of the fetus, and the level of sodium in the amniotic fluid.
From page 254...
... Infants and Children The sodium requirement is obviously highest In Infants anct young children in whom extracellular fluid volume is rapidly expanding. Forbes (1952)
From page 255...
... Dietary Sources anc! Usual Intakes Potassium is widely distributed in foods, since it is an essential constituent of all living cells.
From page 256...
... The contribution of drinking water to potassium intake is negligible. The mean concentration in household tap water was reported to be 2.15 m/liter (range.
From page 257...
... CHLORIDE . Chloride, the principal inorganic anion in the extracellular fluid compartment, is essential in maintaining fluid and electrolyte balance, and is a necessary component of gastric juice.
From page 258...
... Estimate of Requirements Because both the intake of chloride from food and its losses from the body under normal conditions parallel those of sodium, the requirements specified for all age and sex groups except infants parallel those of sodium on a mEq basis (see Table 11-1~. Human milk contains 11 mEq of chloride per liter, which makes the chloride level higher than the sodium level on a mEq basis.
From page 259...
... Federal/State Survey of' Organics and Inorganics in Selected Drinking Water Supplies.
From page 260...
... 1977. Sodium and potassium intakes and excretions of normal men consuming sodium chloride or a 1:1 mixture of sodium and potassium chloride.
From page 261...
... 1981. Hypokalemic metabolic alkalosis in normotensive infants with elevated plasma renin activity and hyperaldosteronism: role of dietary chloride deficiency.


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