PEDIATRICS Vol. 78 No. 3 September 1986, pp. 465-472
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Energy Metabolism and Substrate Utilization in Low Birth Weight Neonates Under Radiant Warmers

Keith H. Marks MB, BCh, FCP, MRCP1, Elizabeth E. Nardis BS1, and Malik N. Momin BS1

1 From the Departments of Pediatrics, The Milton S. Hershey Medical Center, The Pennsylvania State University, College of Medicine, Hershey

We evaluated the metabolic response to the thermal demands of an open radiant warmer device, as distinct from convection incubator, in 13 healthy pre-mature infants (1,395 ± 169 g, 28 ± 12 days of age, mean ± SD). Metabolic rate was 10% higher for infants under the radiant warmer than in the incubator (2.60 ± 0.4 v 2.36 ± 0.3 kcal/kg/h; P < .05). The radiant warmer also induced a small (4%), but significant, increase in nonprotein respiratory quotient (0.94 ± 0.1 v 0.90 ± 0.1; P < .05) and a 13% increase in carbon dioxide production (8.26 ± 1.1 v 7.31 ± 1.1 mL/kg/min; P < .05). Subcutaneous fat accumulation (estimated from 60-second skin-fold thickness measurements) was greater under the radiant warmer than in the incubator (0.08 ± 0.05 v 0.04 ± 0.04 mm/d; P < .05). Under the warmer, the infant's mean skin temperatures and core temperatures were normal and similar to those found in the incubator, but the foot temperature was on average 0.6°C cooler. The average rate of weight gain (18 g/kg/d) was the same in the radiant environment. The pattern of the elevated metabolic rate, shift of respiratory quotient coupled with the accumulation of subcutaneous fat, and cool extremities of infants under the radiant warmer may represent a physiologic adaptive response to thermal stress. However, the reasons for the elevated metabolic rate are unclear, because activation of the sympathetic nervous system with the release of catecholamines is not apparently involved. We speculate that change in metabolic activity is more likely related to alterations in sleep and/or behavior patterns in the exposed environment. Given this relatively short-term study of healthy premature infants receiving an excellent caloric intake (120 kcal/kg/d), we conclude that radiant warmers produce no short-term metabolic complications or adverse effects on growth. Although the clinical importance of elevated metabolic rates in infants under radiant warmers is currently uncertain, our data suggest the need for caution in the long-term use of these devices.

Key Words: premature infant • radiant warmer • incubator • calorimetry • thermoregulation

Accepted on November 25, 1985




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M. P. Meyer, M. J. Payton, A. Salmon, C. Hutchinson, and A. de Klerk
A Clinical Comparison of Radiant Warmer and Incubator Care for Preterm Infants From Birth to 1800 Grams
Pediatrics, August 1, 2001; 108(2): 395 - 401.
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