EFFECTS OF WITHHOLDING FLUID IN THE IMMEDIATE POSTNATAL PERIOD
Authors: HANSEN JOHN D. L. , SMITH CLEMENT A. 
Published: December 2021

These studies were undertaken primarily to evaluate the importance of fluid intake soon after birth and to determine whether consequences of its omission are modified by the relative excess of water in the body of the newborn infant. Weight losses, outputs of Na, K, Cl, N and water, and serum concentrations were investigated in nine infants receiving no intake for 72 hours after birth and in nine controls receiving approximately 50 cc. water/kg. daily. In seven other infants, 2.5 to 10% glucose was added to the water intake of the first three days.

The results can be summarized as follows:

1. The amounts of electrolytes and nitrogen excreted in the urine were unaffected by water intake. Thus, infants of 36 weeks or more in gestational age excreted averages of about 0.3 mEq. of Na, 0.45 mEq. of K, 0.35 mEq. of Cl and 80 mg. N/kg. daily during three days after birth, whether or not water was provided. The average weight loss of 13% in three days without water intake as against 8% when water was given indicates the greater loss of body water necessitated if fluid is withheld.

2. Five infants of less than 35 weeks' gestational age excreted amounts of electrolytes 2 to 3 times larger (and somewhat larger amounts of nitrogen) per kg. of body weight than did the more mature infants. Again, the excretions were uninfluenced by water intake. The weight losses of these more premature infants were increased by omission of water intake to about the same degree as in the less premature or full-term ones similarly restricted.

3. In infants of all gestational ages studied, omission of water produced a rather uniform increase in urine concentration; the highest osmolarity of 680 mOsm./l. on the third day was in the urine of a premature infant. Concentrations of Na and Cl in the serum, and of B.U.N. rose in all infants not receiving water, again without regard to maturity.

4. The measurements obtained from infants were compared on the basis of surface area with values which have been established for adults. On this comparison, daily losses of body weight, and thus of body water, were approximately similar for infants and adults during fasting with and without water intake, but outputs of electrolytes by the infants were relatively reduced.

5. The provision of water and glucose to infants, either on the fourth day following birth, or instead of water alone during the first three days, resulted in conservation of body water, but no sodium- or nitrogen-sparing was demonstrated.

While possible explanations of these various results are considered above, it seems reasonable to draw a few broad and clinically applicable conclusions here. The composition of the infant at birth affords no protection against the chemical consequences of water deprivation. Age-conditioned limitations in concentration of urine result in inefficient conservation of body water and, therefore, in the occurrence of hemoconcentration before it would take place in the adult. Although thus unable to maintain homeostasis, the clinically satisfactory status of the infants studied and their prompt return to normal serum concentrations after one subsequent day of water and glucose administration suggests their tolerance of three days without water intake. When fluid is given during the immediate postnatal period, the results of this study suggest that body water will be conserved if the fluid be glucose solution rather than plain water.