Responses of the newborn infant to overheating.

The responses of newborn babies to overheating were investigated by exposing them to progressively higher incubator air temperatures until either sweating occurred or the rectal temperature reached 37.9 degrees C. 112 studies were performed on 83 healthy term and preterm infants. Activity, posture, heart rate, respiratory rate, skin colour and abdominal skin and hand temperature were monitored. Most babies regardless of gestational age became less active, and they frequently fell asleep at the warmest setting. The majority of infants altered their posture from predominantly flexion to extension. There were no significant changes in heart rate or respiratory rate. The skin of almost all the babies became redder, and the difference between central and peripheral skin temperatures decreased with warming. The pattern of these changes varied with maturity suggesting the development of vasomotor control. It is a surprising finding that even the most immature babies appear to make appropriate responses to heat stress. These responses may aid in the recognition of a baby who is too warm.