THERMAL BALANCE AND METABOLIC-RATE DURING UPPER RESPIRATORY-TRACT INFECTION IN INFANTS

Sequential recordings were made in the first five months after birth o f metabolic rate, environmental temperature, and body temperature duri ng sleep at home in 17 infants, each with an older sibling. Further re cordings were made whenever an older sibling developed an upper respir atory tract infection (URTI), again four to six days later, and again two weeks later, aiming to achieve recordings before, during, and afte r an URTI in the infant. The temperature of the room and wrapping of t he infant were determined according to their usual practice by the par ents. Parents added appropriate wrapping to achieve thermal neutrality based on our calculated values and the measured oxygen consumption. I n five of the six infants who developed an URTI in the first three mon ths after birth there was no change or a decrease in metabolic rate at the time of the infection; for infants older than 3 months the metabo lic rate increased in three of the five episodes recorded. Peripheral skin temperature decreased at the time of URTI at all ages. though in the older infants it usually increased in parallel with rectal tempera ture during the latter part of the night, when pyrexia was most common . Infants thus respond to URTI by heat conservation. In the younger in fants the lower metabolic rate and the further decrease in this rate w ith URTI means that fever is rare, and their temperature may decrease on infection. In the older infants the increase in metabolic (from alr eady higher baseline) result fever. These differences contribute to th e increased vulnerability of the older infants to heat stress, particu larly at the time of acute viral infections.