Thermal Stability of the Premature Infant in Neonatal Intensive Care

Robin B. Knobel, PhD, RN


NAINR. 2014;14(2):72-76. 

In This Article

Normal Body Temperature

The main goal of achieving thermal stability in a premature infant is to maintain a normal body temperature. Before we can discuss ways in which this goal can be accomplished, we first need to agree on the definition of normal body temperature. Temperature will vary with the site that is measured and the device with which temperature is measured. Neonatal textbooks give general temperature ranges for premature infants by site with rectal being 36.5 °C to 37.5 °C, skin as 36.2 °C–37.2 °C, and 36.5 °C to 37.3 °C for axillary sites.[2] The 2012 American Academy of Pediatrics/American Congress of Obstetricians and Gynecologists prescribe an axillary temperature standard of 36.5 °C in the delivery room and an axillary temperature range of 36.5 °C to 37.4 °C prior to discharge for an infant in an open crib in clothing.[3] Therefore, it should be a minimal safe standard to require all infants in the NICU maintain an axillary temperature of at least 36.5 °C. Because extremely low birth weight (ELBW) infants are more like poikilotherms (similar to a cold blooded animal or reptile) and have unstable body temperature which tends to follow environmental temperature, these infants should be kept warmer to minimize the chance of cold stress.[4] We previously found that ELBW infants have more stable heart rate values when kept at a central skin temperature of 36.8 °C to 36.9 °C during their first day of life.[5] Our research and that of others have also underscored the importance of monitoring two temperature sites on premature infants while cared for in the NICU.[6–8] ELBW infants have immature thermoregulation and have periods of time where they keep their peripheral temperature warmer than their central temperature.[6,7] This state is undesirable and may increase the chances of morbidity. It is imperative to monitor for this condition and minimize procedures, feedings and stimulation to the infant if the central temperature is low. Good temperature monitoring and adherence to a minimum axillary temperature level such as 36.5 °C are the first important steps to thermal stability.