The Effect of Sleep State on Active Thermoregulation in the Premature Infant

Abstract

Summaryduring extended periods might heavily contribute to the overall Alterations in thermoregulatory mechanisms related to sleep state may play an important role in the problems of homeostasis experienced by the premature infant. In the adult, homeothermic regulation of body temperature may. be suspended during REM. We measured oxygen consumption (VOz) in six premature infants 33-35 wk gestation both at thermoneutrality and during a mild thermal stress to determine whether thermoregulatory responses were intact during REM sleep. All infants were studied under radiant warmers. Skin temperature was allowed to fall 7-8 times during a 6-8 h study period while VOz, VCOZ, heart rate and TcPOz were continuously recorded. Sleep state was scored using EEG, EOG, EMG and behavioral criteria. A total of 1,162 onemin epochs were scored. In all states including REM, VOZ was significantly higher during the cool periods. The mean increases: 21.5%, 23.3%, 11.1% and 5.3% for Awake, Indeterminate, REM and NREM respectively. When REM and NREM were compared at thermoneutrality, there was no difference in the VOZ (8.80 + 0.11 and 8.93 f 0.15 cc/kg/min, mean f S.E., for REM and NREM, respectively). We conclude that in contrast to the adult, active thermoregulation occurs in the premature infant during REM sleep. SpeculationIn the adult, the reason for temporary poikilothermy during REM sleep is unknown. Some have considered this phesomenon a regression to a phylogenetically primitive condition which is necessarv for normal hvpothalamic function. Because the newborn " -period is characterized by profound ontogenic change, it is reasonable to s~eculate that the difference we observed between the premature and the adult is due to a developmental phenomenon. We further suggest that this developmental process may serve to protect the premature infant during REM sleep from extended periods of poikilothermy.Alterations in thermoregulatorv mechanisms related to sleep state may play an importaGt role the problems of homeostask ex~erienced bv the Dremature infant. Verv little information is av'ailable conckrning'the effects of arousal itate on the control of body temperature. As early as 1941, Day (4) observed a fall in rectal temperature with the onset of sleep in children. The decline in rectal temperature was coincident with increased evaporative water loss and rise in skin temperature indicating that the observed changes were possibly regulated phenomenon.In the adult, homeothermic regulation of body temperature may be suspended during REM sleep (9). Normal responses to cooling, such as shivering and vasomotor activity, seem to be absent during REM. Likewise, panting, sweating and vasomotor responses to warming also seem to be nonfunctional during REM (1 1). In contrast to the adult and older child, the newborn spends more time in REM sleep. A suspension of body temperature regulation poor control of body temperature in these infants.There has been little reported concerning the ability of the newborn to actively thermoregulate during sle...

Day-to-Day Energy Expenditure Variability in Low Birth Weight Neonates

“…The coefficient of variation (mean + SEM) during each 2-h measurement of gaseous metabolism within the same infant was 10 + 1.2% and 12 + 1.9% for VOz and VC02, respectively. This spontaneous variability of respiratory gas exchange within individual measurements may be attributed to the expected relationship between VOz, VC02, and state of activity (quiet sleep, active sleep, and quiet wakefulness) over the measurement period and was within the range of previous findings (21)(22)(23)(24). Table 2 summarizes the results from the longitudinal measurements of V02, VC02, and TUN excretion for each infant.…”

Sleep Organization and Energy Expenditure of Breast-Fed and Formula-Fed Infants

“…In another series of seven neonates, a 9.4% increase in Vo2 was shown in the transition from NREM to REM (9). Equivocal results have been reported for preterm infants: Scopes and Ahmed (8) detected a 16% increase in Vo2, and Darnall and Ariagno (24) showed no difference in Vo2 between REM and NREM. Conflicting results have been reported on adults; some investigators have detected significant increases in energy expenditure during REM sleep (25,26), whereas others have not (27,28).…”

The carotid body and arousal in the fetus and neonate

“…Thus brown fat metabolism, shivering and sweating are all suspended during REM (Parmeggiani & Rabini, 1967; Parmeggiani et al , 1977). In the human infant, however, thermoregulation is preserved during REM sleep, and may even be more effective (Stothers & Warner, 1977a, b; Darnall & Ariagno, 1982). …”