Thermal Environment and Acid-Base Homeostasis in Human Infants during the First Few Hours of Life*

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Abstract
It is known that labor and delivery result in varying degrees of respiratory and metabolic acldosis. The optimal thermal environment for recovery from this is unknown. Twenty-four healthy term infants were studied; 12 were kept warm, body temperature being maintained at 37[degree]C, 12 were exposed to room temperature (25[degree]C). In addition serial observations were made in 8 healthy and 4 depressed infants under both warm and cool conditions. Body temperatures and oxygen consumption were monitored and serial samples were obtained for acid-base analysis. In the cool group body temperature fell, the rate being more rapid immediately after birth. Both the warm and cool healthy infants were able to achieve and maintain a relatively normal pH. In the cool infants there was evidence of an increased metabolic acidosis accompanied by a compensatory lowering of the carbon dioxide tension and an increase in oxygen consumption. The depressed infants were unable to respond to cold stress in this way, the pH fell, metabolic acidosis was more marked and the increase in oxygen consumption was less. It is concluded that mild cold stress induces metabolic acidosis in newborn infants which is more pronounced in those who are depressed at birth.