WATER EXCHANGE OF PREMATURE INFANTS—COMPARISON OF METABOLIC (ORGANIC) AND ELECTROLYTE (INORGANIC) METHODS OF MEASUREMENT 12

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Abstract
8 periods of water and electrolyte balance, totalling 48 days, were concurrently made on 4 premature [male] infants, on diets adequate to produce wt. gains of 25 to 49 g. daily. In the organic method the water balance was detd. from the wt. and water content of intake, urine, feces, and insensible loss, and the composition of the metabolic mixture (g. of protein, fat, and CHO oxidized). In the inorganic method, Cl, N, Na and K retentions were used to calculate the water retention. The close agreements between the results of both methods in 5 of 8 periods suggest that under controlled environmental and dietary conditions, either method of predicting the water balance of thriving premature infants is satisfactory. In 2 of 3 periods in which perceptible perspiration was present, the unmeasured excretions of electrolytes through the skin presumably credited the subjects with falsely high retentions of electrolytes and water. Under such conditions the organic method estimated water balances more reliably. The similarity between the actual retentions of Na, K and P and their retentions as calculated from the Cl, Ca and N retentions, and the fact that the water balance as computed from electrolyte balances represented about 70% of the body wt. gain, indicate that in normal growth electrolytes are retained in approximately the relations to one another that exist in body tissues.