title: Severe hypercapnia causes reversible depression of aEEG background activity in neonates: an observational study.
abstract: BACKGROUND
  Elevated carbon dioxide (CO2) blood levels have a depressant effect on the central nervous system and can lead to coma in adults. Less is known about the effect of CO2on the neurological function of infants.
  
  
  OBJECTIVE
  To describe the effect of acute severe hypercapnia (PaCO2>70 mm Hg) on amplitude-integrated electroencephalography (aEEG) and cerebral oxygenation in newborn infants.
  
  
  METHODS
  Observational study of full-term and preterm infants with acute severe hypercapnia (identified by arterial blood gas measurements), monitored with aEEG. Visual analysis of the aEEG was performed in all infants. In preterm infants <32 weeks postmenstrual age (PMA), analysis of two-channel EEG was performed. Mean spontaneous activity transients (SAT) rate (SATs/min), interval between SATs (ISI in seconds) and the ISI percentage (ISP) were calculated for 10-min periods before, during and after hypercapnia. Mean regional cerebral oxygen saturation (rScO2) and fractional tissue oxygen extraction (FTOE) measured with near-infrared spectroscopy were also calculated for these periods.
  
  
  RESULTS
  Twenty-five infants (21 preterm, 4 full-term) comprising 32 episodes of acute severe hypercapnia were identified. Twenty-seven episodes were accompanied by a transient aEEG depression. Twenty-two episodes in 15 preterm infants <32 weeks PMA were quantitatively analysed. During hypercapnia, SAT rate decreased and ISI and ISP increased significantly. No significant change occurred in rScO2or FTOE during hypercapnia.
  
  
  CONCLUSIONS
  Profound depression of brain activity due to severe hypercapnia is also seen in infants. It can be recognised by an acute depression of the aEEG, without clinically detectable changes in cerebral oxygenation.
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Weeke
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Laura M L
authors.initials: LML
authors.lastname: Dix
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Floris
authors.initials: F
authors.lastname: Groenendaal
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Petra M A
authors.initials: PMA
authors.lastname: Lemmers
authors.affiliation: Department of Neonatology, Máxima Medical Centre, Veldhoven, The Netherlands.
authors.forename: Koen P
authors.initials: KP
authors.lastname: Dijkman
authors.affiliation: Department of Neonatology, Máxima Medical Centre, Veldhoven, The Netherlands.|Department of Pediatrics, Faculty of Health, Medicine and Life Science, University of Maastricht, Maastricht, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Andriessen
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Linda S
authors.initials: LS
authors.lastname: de Vries
authors.affiliation: Department of Neonatology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Mona C
authors.initials: MC
authors.lastname: Toet
mesh_terms: D001921:Brain / Q000378:metabolism*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000378:metabolism*; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D047929:Term Birth
chemical_list: D010100:Oxygen
keywords: CO2; cerebral oxygenation; cortical activity