Radiant Heat Loss versus Radiant Heat Gain in Premature Neonates under Radiant Warmers

Premature infants nursed on open radiant warmer beds are exposed to short-wavelength infrared power density distributed evenly over the bed surface. Additionally, infants’ sides are exposed to relatively cooler nursery walls, and to the radiant warmer bed platform which may heat and reradiate to the baby. Therefore, infants may not only gain heat from the warmer (Q_{radiant warmer}) but lose or gain radiant heat to the sides as well ( ± Q_{radiant loss}). In order to quantitate these parameters, ten premature newborn infants nursed under radiant warmers servocontrolled to 36.5 °C skin temperature (weight 1.27 ± 0.24 SD kg, gestation 31 ± 3 weeks) were investigated, and partitional calorimetry previously reported. In the present study, calculation of net rate of radiant heat transfer (Q_{net radiant}) was made from these data (––2.63 ± ––1.52 kcal/kg/h), and compared to direct measurements of Q_{radiant warmer} (––2.49 ± ––0.90 kcal/kg/h). The present report further partitions net radiant heat transfer to evaluate Q_{radiant loss}: ––0.13 ± 1.82 kcal/kg/h (range-3.16 to 1.93). From these calculations mean radiant temperature of this environment was estimated (45.3 ± 4.3 °C) and compared to the radiant warmer temperature received (45.0 ± 2.9 °C). This information suggests other strategies to reduce radiant heat loss as well as convective and evaporative losses in premature neonates nursed on open radiant warmer beds.