New standards for neutral thermal environment of healthy very low birthweight infants in week one of life.

It is generally accepted that low birthweight infants should be nursed at thermal neutral temperature--the environment in which oxygen consumption is at a minimum. Low birthweight infants do not, however, always show an increase in oxygen consumption at a temperature outside the neutral range, but react with a change in body temperature. We redefined therefore the neutral temperature for these infants as 'the ambient temperature at which the core temperature of the infant at rest is between 36.7 and 37.3 degrees C and the core and mean skin temperatures are changing less than 0.2 and 0.3 degrees C/hour respectively'. Using this definition, new guidelines of the neutral temperature have been made for healthy infants of 29-34 weeks' gestation. The neutral temperature during the first week of life is dependent on gestational age and postnatal age, whereas after the first week it depends on body weight and postnatal age. Using this definition and the guidelines, the appropriate environmental temperature for the individual patient can be chosen.