The Metabolic Response of Infants to Heat Stress *

The physiological adjustments of man to high environmental temperatures have been studied extensively in the adult. However, the influence of environmental temperature on the water and electrolyte balance of infants has not been adequately determined. This paper reports the changes in the distribution of body water and electrolyte which occurred in infants exposed to heat stress. Accurate balances were assured by the determination of skin losses. The most striking result of exposure to high environmental temperatures is the production of sweat. Adolph2 has summarized most of the work on this subject and has shown that the volume of sweat is proportional to the heat load. The concentration of sodium and chloride in the sweat of unacclimatized adults has been determined by many workers." '9U 5,36,"4,7,49 The reported concentrations vary from 10 to 140 mM per liter. The higher values may be erroneous because of evaporation occurring during the collection of sweat. Johnson, Pitts, and Consolazio' have summarized the factors which may modify the electrolyte composition of sweat. Desoxycorticosterone acetate lowers the chloride concentration of the sweat in adults.'6 Similarly, adrenal cortical extract decreases the concentration of sodium and chloride and raises the concentration of potassium."' Although it is known that the sweat of infants contains electrolyte,' the exact concentiations have not been measured. Under conditions in which there was probably little sweating, Romminger and Meyer42 and Swanson and Iob4 found an appreciable loss of electrolyte from the skin. The latter workers found significant amounts of potassium in the skin washings of infants under one year of age kept at room temperature of 780F. while dressed in light clothing. Approximately 1.7 mM of potassium per day or 35 per cent of the apparent retentions, excluding