title: Assessing neonatal heat balance and physiological strain in newborn infants nursed under radiant warmers in intensive care with fentanyl sedation.
abstract: OBJECTIVE
  To assess heat balance status of newborn infants nursed under radiant warmers (RWs) during intensive care.
  
  
  METHODS
  Heat balance, thermal status and primary indicators of physiological strain were concurrently measured in 14 newborns nursed under RWs for 105 min. Metabolic heat production (M), evaporative heat loss (E), convective (C) and conductive heat flow (K), rectal temperature (T re) and mean skin temperatures (T sk) were measured continuously. The rate of radiant heat required for heat balance (R req) and the rate of radiant heat provided (R prov) were derived. The rate of body heat storage (S) was calculated using a two-compartment model of 'core' (T re) and 'shell' (T sk) temperatures.
  
  
  RESULTS
  Mean M, E, C and K were 10.5 ± 2.7 W, 5.8 ± 1.1 W, 6.2 ± 0.8 W and 0.1 ± 0.1 W, respectively. Mean R prov (1.7 ± 2.6 W) and R req (1.7 ± 2.7 W) were similar (p > 0.05). However, while the resultant mean change in body heat content after 105 min was negligible (-0.1 ± 3.7 kJ), acute time-dependent changes in S were evidenced by a mean positive heat storage component of +6.4 ± 2.6 kJ and a mean negative heat storage component of -6.5 ± 3.7 kJ. Accordingly, large fluctuations in both T re and T sk occurred that were actively induced by changes in RW output. Nonetheless, no active physiological responses (heart rate, breathing frequency and mean arterial pressure) to these bouts of heating and cooling were observed.
  
  
  CONCLUSIONS
  RWs maintain net heat balance over a prolonged period, but actively induce acute bouts of heat imbalance that cause rapid changes in T re and T sk. Transient bouts of heat storage do not exacerbate physiological strain, but could in the longer term.
authors.affiliation: Thermal Ergonomics Laboratory, Faculty of Health Sciences, University of Ottawa, Ottawa, Canada.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Molgat-Seon
authors.forename: Thierry
authors.initials: T
authors.lastname: Daboval
authors.forename: Shirley
authors.initials: S
authors.lastname: Chou
authors.forename: Ollie
authors.initials: O
authors.lastname: Jay
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology / Q000627:therapeutic use*; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology*; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005283:Fentanyl / Q000494:pharmacology / Q000627:therapeutic use*; D006358:Hot Temperature; D006801:Humans; D007186:Incubators, Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D015931:Intensive Care, Neonatal; D008297:Male; D012127:Respiratory Distress Syndrome, Newborn / Q000188:drug therapy / Q000628:therapy*; D012881:Skin Temperature / Q000187:drug effects / Q000502:physiology
chemical_list: D000701:Analgesics, Opioid; D005283:Fentanyl