title: Influence of sympathetic activity in the control of peripheral microvascular tone in preterm infants.
abstract: Microvascular dysregulation following preterm birth is associated with increased illness severity and hypotension, particularly in males. Sympathetic nervous vascular regulation is evident in females. We hypothesized that sympathetic dysfunction in male preterm infants may contribute to a failure of peripheral microvascular vasoconstriction.
  
  
  
  Microvascular blood flow of infants 24-43 wk gestational age was assessed at 6, 24, and 72 h of age by laser Doppler. Blood flow Fourier transformed frequency distribution spectra (low frequency/high frequency ratio) were used to assess the influence of sympathetic tone on microvascular regulation. Total sympathetic output was assessed as urinary normetanephrine.
  
  
  
  Microvascular sympathetic activity at 24 h postnatal age decreased in early preterm males, but not females. Peripheral sympathetic activity increased with advancing postnatal age in females, but decreased in males. In early preterm infants, total normetanephrine outputs increase significantly with postnatal age, in both sexes.
  
  
  
  Sympathetic activation following preterm birth is sexually dimorphic, with preterm males having reduced sympathetic tone and reduced upregulation of sympathetic tone following birth. There is evidence of a disconnect between central sympathetic activity and local peripheral microcirculatory sympathetic drive. This may relate to autonomic nervous immaturity and highlights the need to understand how preterm birth may affect autonomic function.
authors: Mothers and Babies Research Centre, Hunter Medical Research Institute, and Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.
authors: Celine
authors: C
authors: Corbisier de Meautsart
authors: Mothers and Babies Research Centre, Hunter Medical Research Institute, and Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|Illawarra Health and Medical Research Institute, and Graduate School of Medicine, University of Wollongong, Newcastle, Australia.
authors: Rebecca M
authors: RM
authors: Dyson
authors: Mothers and Babies Research Centre, Hunter Medical Research Institute, and Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.
authors: Joanna L
authors: JL
authors: Latter
authors: Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand.
authors: Mary J
authors: MJ
authors: Berry
authors: Mothers and Babies Research Centre, Hunter Medical Research Institute, and Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|The Robinson Institute, Lyell McEwin Hospital, University of Adelaide, Adelaide, Australia.
authors: Vicki L
authors: VL
authors: Clifton
authors: Mothers and Babies Research Centre, Hunter Medical Research Institute, and Discipline of Paediatrics and Child Health, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|Illawarra Health and Medical Research Institute, and Graduate School of Medicine, University of Wollongong, Newcastle, Australia.|Kaleidoscope Neonatal Intensive Care Unit, John Hunter Children's Hospital, New Lambton Heights, Australia.
authors: Ian M R
authors: IM
authors: Wright
mesh_terms: D005260:Female; D006801:Humans; D062071:Infant, Extremely Premature / Q000502:physiology; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D009647:Normetanephrine / Q000652:urine; D012727:Sex Characteristics; D013564:Sympathetic Nervous System / Q000502:physiology*
chemical_list: D009647:Normetanephrine