Postoperative water, electrolyte and nitrogen balances were estimated in 10 newborn infants who had undergone surgical operations within the first 4 days of life, and the results were compared with those obtained from 20 normal newborn infants.
In newborns, responses to the operation were markedly different from those of adults or older infants. Postoperative oliguria was not observed. Daily administration of water in more than 80ml/kg/day, however, resulted in definite accumulation of body water. The dose of given water (
x) and the water balance (
y) were proportional to each other, and their correlation was given by an expres-sion in the form of
y=0.75
x-27. Adequate amount of water to be given to new-born infants in early postoperative periods seemed to be 60ml/kg/day.
Urinary excretion of sodium chloride in postoperative newborns was larger than that of normal newborns in the comparable age. Urinary excretion of potassium in the operative group was slightly larger than that of the control group. Urinary potassium-nitrogen ratio in postoperative newborns was within the ratios for the normal lean muscle tissue.
Administration of 10μg/kg of aldosterone caused little change in urinary electrolyte excretion and urinary sodium-potassium ratio in newborn infants, though it caused a marked increase in urinary potassium excretion and urinary sodium-potassium ratio in older infants. Immature response of the kidney of newborn infants to aldosterone seems to be one of the principal factors causing the postoperative electrolyte metabolism characteristic of newborn infants within a few days of birth.
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